UNIVERSITY OF CALIFORNIA
COLLEGE OF AGRICULTURE
AGRICULTURAL EXPERIMENT STATION
BERKELEY, CALIFORNIA
DISEASES OF CHICKENS
J. R. BEACH and M. A. STEWART
BULLETIN 674
November, 1942
UNIVERSITY OF CALIFORNIA
BERKELEY, CALIFORNIA
CONTENTS
PAGE
General considerations of disease
and of control measures 3
Types of poultry disease 3
Breeding for disease resistance . . 5
Types of measures for the control
of infectious diseases and para-
sites 6
Sanitary considerations in the
construction, equipment, and
care of poultry houses 7
Sanitation of poultry yards 11
Disinfection and disinfectants. . . 12
Direct Sunlight 13
Heat 13
Disinfecting with chemicals ... 14
Details of disinfection 15
Phenol, or carbolic acid 16
Cresol, or cresylic acid 16
Crude carbolic acid 16
Saponified cresol solutions 16
Sheep-dips 17
Chlorine disinfectants 17
Iodine 17
Chlorinated lime (chloride of
lime) 17
Quicklime (unslaked lime, cal-
cium oxide) 17
Lye (sodium hydroxide) 18
Copper sulfate (bluestone) .... 18
Potassium permanganate 18
Bichloride of mercury (corro-
sive sublimate) 18
Sodium orthophenylphenate . . 19
Formalin and formaldehyde gas 19
Paraffin-oil emulsion 21
Lime-sulfur dip 21
Kerosene emulsion 21
Wettable sulfur 21
Creolin 21
Anthracene oil 21
Management practices in prevent-
ing and controlling transmis-
sible diseases 22
Measures to prevent introduc-
tion of infection to a farm. . 22
Measures to prevent the spread
and recurrence of disease on
a farm 24
Medication of drinking water . . 25
Medication of the feed 25
Infectious diseases 26
Pullorum disease (bacillary white
diarrhea) 26
Infectious bronchitis 39
Avian pneumoencephalitis 41
Infectious avian encephalomyeli-
tis (epidemic tremor) 46
PAGE
Infectious laryngotracheitis 47
Infectious coryza, or colds 53
Fowl pox 60
Fowl typhoid 71
Fowl cholera 73
Edema of the wattles 75
Colibacillosis 76
Avian tuberculosis 76
Lymphomatosis 78
Coccidiosis 86
Mycosis of the crop 98
Infection of chickens with human
and equine varieties of sleeping
sickness 99
Nutritional diseases 100
Vitamin-A deficiency 100
Vitamin-D deficiency (rickets) . . . 104
Kiboflavin (vitamin G) deficiency 106
Pantothenic acid (filtrate factor
or antidermatitis vitamin) defi-
ciency 107
Gizzard erosions 108
Perosis (slipped tendon) 108
Nonspecific diseases 110
Cannibalism 112
External parasites 113
General characteristics of mites. . 113
The common poultry mite 114
The scaly-leg mite 117
The depluming mite 118
The tropical fowl mite and the
feather mite, or northern fowl
mite 119
The air-sac mite 121
The subcutaneous mite of fowl. . . 121
The quill mite 121
Differentiating ticks from mites . . 121
The fowl tick, or blue bug 122
Lice 124
General characteristics of fleas. . . 127
The sticktight flea 128
The western hen flea 129
The common house fly 130
Wound-invading maggots 132
The common bedbug and the Mex-
ican chicken bug 134
Internal parasites 135
Flukes 135
Tapeworms 136
General characteristics of round-
worms 141
The large roundworm of poultry. 142
The cecum worm 145
The gizzard worm 146
Hairworms, or capillaria worms . . 148
The gapeworm 149
DISEASES OF CHICKENS
J. R. BEACH 3 and M. A. STEWART 4
GENERAL CONSIDERATIONS OF DISEASE AND OF
CONTROL MEASURES
TYPES OF POULTRY DISEASE
Diseases of poultry may be grouped into three general types: (1)
transmissible diseases caused by specific infectious agents known as
bacteria, viruses, or fungi (molds) and animal parasites, and certain
diseases which appear to be transmissible but for which a specific cause
has not been found; (2) diseases due to specific deficiencies of certain
essential ingredients in the diet; and (3) a group termed "nonspecific,"
which includes those diseases and abnormal conditions not as yet shown
to be associated with infection, parasitism, or dietary deficiencies.
Infectious and parasitic diseases have been the most serious causes of
poultry mortality, and it is these which have received the most attention
since the seriousness of poultry diseases was recognized and intensive
study of them began, about thirty years ago. Knowledge since accumu-
lated, however, has made available to poultry raisers control measures
by which the losses from the majority of these diseases may be kept
within reasonable limits. Diseases of this classification and the means for
their prevention and control constitute the subject with which this bul-
letin is principally concerned.
The diseases definitely related to nutrition are principally those re-
sulting from vitamin deficiencies. The existence of such diseases on
poultry farms in epidemic proportion was first recognized about 1920
and they have become of increasing significance as methods of rearing
and feeding poultry have become more and more artificial. Knowledge
of poultry nutrition, however, has kept pace with dietary deficiency
diseases, and most of this type of trouble can be avoided. In fact, some
1 Received for publication March 11, 1942.
2 This bulletin supersedes Agricultural Extension Circular 8, Diseases and Para-
sites of Poultry in California, by J. R. Beach and S. B. Freeborn. That circular, after
five editions, is now out of print. The material included in the present bulletin is
strictly factual as far as possible. In cases in which knowledge still is incomplete,
an attempt has been made to present differences of opinion in unbiased fashion.
Most emphasis is given to the disease problems of greatest economic importance to
commercial poultry raisers of California. A major portion of the material presented
is based upon work done at the California Agricultural Experiment Station, but in-
formation obtained from the work of others has been freely used and is hereby ac-
knowledged. The inclusion of extensive bibliographic references, however, has been
omitted.
:i Professor of Veterinary Science and Veterinarian in the Experiment Station.
1 Associate Professor of Entomology and Associate Entomologist in the Experiment
Station.
[3]
4 University oi California — Experiment Station
of the nutritional diseases had been seen in the laboratory before they
were known to have occurred on farms.
There is a tendency to ascribe to the feed much of the sickness among
poultry which may appear suddenly or which is of an obscure nature,
but in most cases it is impossible to determine that the feed is at fault.
Sickness caused by a spoiled ingredient in a ready-mixed mash has been
encountered occasionally, however, and losses from food poisoning in
PHARYNX
1ST. PORTION,
2ND. PORTION,
ESOPHAGUS
Fig. 1. — Diagram showing the location of anatomical parts of chickens.
flocks which are fed kitchen refuse or garbage are fairly common. In
the latter case the poisonous material is usually spoiled canned fruit,
vegetables, or meat, which causes a disease known as "botulism" or
"limberneck."
Rations which are compounded from ingredients of good quality on
the basis of present knowledge of poultry nutrition are not likely to be
the cause of sickness and death. But rations designed to stimulate very
high egg production or very rapid growth are apt to be responsible for
loss of birds. Poultrymen should be guided by the recommendations of
poultry departments of the agricultural experiment stations, 5 or other
reliable sources of information, to ensure that their feeding practices
are sound, and that they secure the benefit of the new developments in
poultry nutrition.
3 For the recommendations of the poultry department of this station, see : Alm-
quist, H. J., T. H. Jukes, and W. E. Newlon. Feeding chickens. California Agr. Ext.
Cir. 108:1-41. Eevised 1940.
Bul. 674] Diseases of Chickens
BREEDING FOR DISEASE RESISTANCE
The possible application of selective breeding to the reduction of
poultry disease and mortality is well stated in the following excerpts
from Bulletin 626 :
"Some poultrymen are prone to suggest that, if birds are properly
selected and mated, strains will be created with such inherent vigor that
they can withstand adverse conditions commonly found on poultry
ranches. But this seems more than can logically be expected to result
from good breeding. Inadequate or deficient rations, insanitary condi-
tions, and generally poor management cannot be overcome by better
breeding of poultry."
"Some experimental evidence of the inheritance of resistance to spe-
cific infections in chickens has been obtained. Roberts and Card (1926
and 1936) have demonstrated inherited differences in susceptibility to
pullorum disease, and Lambert and Knox (1932) obtained similar re-
sults with fowl typhoid. They failed, however, to obtain strains in which
all the birds were resistant. Furthermore, such diseases can be more
efficiently controlled by other means. On the other hand, there is evi-
dence on the hereditary nature of resistance to certain other disease
conditions for which methods of prevention and control are not yet
known. This applies particularly to neurolymphomatosis (paralysis)
and may also be true of other forms of lymphomatosis (big-liver disease
or leukemia), leucosis, and certain types of tumors." [See p. 78.]
"Losses from pathology associated with the digestive system in the
1933 flock were unusually high and were found predominantly in the
families from one male and his son. After elimination of these families,
losses from disorders of the alimentary system dropped sharply for the
succeeding years."
"All available evidence indicates that disease resistance is specific
in nature. Creating a strain resistant to one disease does not mean that
the strain will be resistant to any other disease. Nor does it mean that
the strain will be unusually susceptible to some other disease. Geneti-
cally, every disease presents a separate problem of breeding for resist-
ance. Whether or not genetics can be effectively applied to the control
of all diseases is questionable."
"Breeding for disease resistance is slow and costly. Where adequate
means are available to control diseases by means of agglutination tests,
vaccines, specific drugs, or sanitation, trying to breed for resistance is
uneconomic. Where no means of control are available and where there
are evidences of different responses by birds of different strains or fam-
ilies, genetic selection is advisable, even though improvement of the
stock comes slowly." 6
That mortality from nonspecific disease or functional disturbances
of vital organs may be influenced by breeding for longevity is indicated
by additional excerpts from the same source.
6 Taylor, L. W., and I. M. Lerner. Breeding for egg production. California Agr.
Exp. Sta. Bul. 626:21, 22, 23, 43, 44. 1938.
6 University of California — Experiment Station
"Just how much .... mortality is due to inherited factors cannot be
estimated accurately, but there is good evidence in many cases that at
least part of the mortality up to the completion of the first laying year
is controlled by genetic factors, and hence the condition is amenable to
improvement by proper breeding methods."
". . . . Greater vitality will ensue in a flock as a consequence of selection
of longer-lived strains. Differences in mortality between families in the
same flock are known to persist for several generations, as they have in
the California Station flock, and hence are probably heritable. Despite
the poultryman's interest in obtaining long-lived birds, comparatively
few reports are available on the results of selection for longevity. This
fact may indicate that breeding for characters influencing longevity is
a complex process."
TYPES OF MEASURES FOR THE CONTROL OF INFECTIOUS
DISEASES AND PARASITES
There are two types of measures or procedures which are useful in the
prevention and control of infections and parasitic diseases. The first
consists of the specific measures, such as vaccination for fowl pox or
spraying with an oil to destroy mites, which are effective against a spe-
cific germ or parasite. These are taken up later in the discussions of in-
dividual diseases. The second type includes the more general measures
which are embraced by the term "sanitation" and which apply to all.
In its broader aspect, sanitation may be defined as providing a place
in which chickens may live safely and produce efficiently. More specifi-
cally, it consists of protecting them from undue exposure to infection
and parasites. The effective application of sanitary measures must,
therefore, be based upon knowledge of how infection and parasitism
are spread from fowl to fowl or from pen to pen on a farm, perpetuated
on a farm from year to year, and introduced on a farm for the first time.
Different diseases are spread in very different ways. Transmission of
infection from one bird to another or from pen to pen may be by birds
actively diseased or by birds that have nearly or entirely recovered from
some disease but which continue to carry the disease-producing agent.
These latter are often referred to as "latent cases of infection" or as
"healthy carriers." This is the common means by which respiratory
diseases are spread and perpetuated on a farm.
Certain diseases are known to be spread and transmitted by insect
vectors, such as flies and mosquitoes. In districts where the latter are
very plentiful, fowl pox, which is spread by them, is more difficult to
control.
The sanitary procedure for a farm must be designed to cope with the
particular disease problem which is present. For example, the separation
of young birds from the old may be of greater importance in controlling
Bul. 674] Diseases of Chickens 7
a certain disease or preventing its spread than maintaining proper clean-
liness. In many cases, however, it is extremely difficult or impossible to
determine how the disease is introduced or is carried from one place to
another. Therefore, it is necessary to employ general sanitary measures
which apply to any type of infection.
Cleaning and disinfection, if properly done, are usually, but not al-
ways, adequate to make a building in which an infectious disease has
occurred safe for further use. However, there are some disease-producing
agents, such as coccidia and the virus of fowl pox, which are so resistant
that they would not be destroyed by disinfection as ordinarily practiced.
In this case, the mechanical removal of infection by cleaning is of really
more importance than the application of disinfectants. That is why, in
a cleaning and disinfection process, the cleaning should be given as much
emphasis as disinfection. The two are complementary ; but the thorough
mechanical cleaning is, perhaps, the more important, at least when
dealing with resistant organisms.
SANITARY CONSIDERATIONS IN THE CONSTRUCTION, EQUIPMENT,
AND CARE OF POULTRY HOUSES
The type of poultry house is not so important as that it possess those
features of design and arrangement that are essential to sanitation.
Floors and foundations should be impervious to moisture, have a smooth,
hard surface to facilitate cleaning, and be rat- and vermin-proof ; con-
crete is the most suitable material. Wood floors are more difficult to
clean and they furnish shelter for rats and vermin. Dirt floors are ob-
jectionable because they cannot be adequately cleaned or disinfected.
The walls should be constructed of matched lumber so as to provide a
smooth surface and be free from cracks that would permit draughts
and in which mites and ticks could find lodging places. The openings
to admit light and for ventilation should be covered with wire netting to
exclude wild birds ; or, better still, with wire screen to exclude insects
as well as birds. They should be large enough to admit plenty of light,
fresh air, and also direct sunlight, exposure to which is beneficial to
fowls and destructive to bacteria. Facilities for ventilation that will
ensure an abundance of fresh air day and night in all kinds of weather
should be provided. The extent to which especial attention must be given
to ventilation depends upon the type of the building, the size of the pens,
and the number of fowls kept in a pen. 7
Droppings boards are optional. If they are installed, chickens should
7 For recommendations on poultry housing, see : Dougherty, J. E., and H. L.
Belton. Poultry houses and equipment. California Agr. Exp. Sta. Bul. 476:1-77.
Revised, 1940, by H. L. Belton and V. S. Asmundson.
University of California — Experiment Station
Fig. 2. — A, A sanitary type of metal feed hopper designed for hanging on the out-
side of a wire-enclosed sun porch ; B, a type of metal feed hopper with wire guard to
exclude chickens and prevent soiling of feed with droppings. (From Bui. 613.)
Fig. 3. — Feed hopper and waterer suitable for chicks. The wire
platform aids in keeping the adjacent area in a sanitary condition.
(From Bui. 613.)
be excluded from them by wire netting beneath the roosts. If they are
not installed, litter will have to be changed more often, which is likely
to be more costly than the daily cleaning of droppings boards would be.
Furthermore, the fertilizer value of droppings undiluted with litter will
be lost and all eggs laid by chickens while on the roost will fall to the
Bul. 674]
Diseases of Chickens
Fig. 4. — A sanitary homemade type of feed hopper of wood construction with
a revolving crosspiece to prevent chickens from roosting above the feed ; adapt-
able for use inside a house or on range. (From Bul. 476.)
Fig. 5. — A sanitary homemade feed hopper that can be installed on the out-
side of a wire fence or sun porch or in the front wall of a poultry house. Feed is
replenished from the outside. (From Ext. Cir. 58.)
floor and be eaten by the other chickens. The latter may cause some of
the chickens to become egg eaters and may be the means of spreading
infections, such as pullorum disease (p. 26), which are transmitted
through eggs.
Feed troughs or hoppers should be of a type that will prevent fowls
from getting in them or roosting over them, and that can be easily
cleaned (figs. 2-5). Removable hoppers are preferable to built-in ones.
10
University of California — Experiment Station
Devices for drinking should be designed to supply fresh, clean water
continuously, and to prevent the floors around from becoming dampened
by overflow or by water scattered by fowls (fig. 6). A continuous
Fig. 6. — A, A sanitary type of water container placed on a wire-mesh plat-
form. This can easily be made automatic by piping water to it and controlling
the flow by means of a float valve. B, A method of supplying chickens with
running water ; the overflow passes into a drainage pit below the lath platform.
It could be made more sanitary by putting a wire guard around the vessel as
in A and by covering the platform with wire mesh. C, Two types of sanitary
waterers made of galvanized metal. The one on the left could easily be made
automatic. D, A good method of supplying water to chickens. The overflow
from the cup is carried through the drain tile to an outside pit or sewer. A
desirable improvement would be increasing the length of the vertical water
pipe and drain tile and surrounding it with a wire-mesh-covered platform.
(From Bui. 613; original for D by courtesy of L. Van Es, University of
Nebraska.)
flow or drip system, arranged so that pollution by droppings cannot
occur, is preferable to open troughs or pans. Water containers should be
surrounded by a wire-mesh-covered platform to exclude fowls from litter
or areas of floor which have become moistened with water scattered by
Bul. 674] Diseases of Chickens 11
the birds when drinking. The exclusion of chickens from the moist areas
around watering devices, in either the houses or the yards, is an impor-
tant factor in general sanitation, and is absolutely essential in the pre-
vention of intestinal parasitism.
When the contour of the land permits, building sites should be selected
that will provide free natural drainage away from the houses. If this is
not possible, a drainage system should be installed.
A regular schedule for cleaning operations should be arranged and
adhered to as carefully as for any other farm operation. Droppings
should be removed from droppings boards daily, whether or not fowls
are excluded from them by wire netting, and stored in flyproof bins or
maggot traps (p. 130) or hauled a considerable distance from the houses.
Litter, in the form of the cheapest absorbent material available, such
as straw, shavings, or rice hulls, should be liberally supplied. If at all
feasible, it should be renewed once a week through the first laying year,
that is, until the birds are about 18 months old. This is the period of
greatest danger from infections and parasitic diseases. If there is no
special infection problem to be dealt with, the litter for older birds ordi-
narily will not require renewal of tener than once a month unless, in the
meantime, it becomes damp. Litter changes should be made more often
in houses which have no droppings boards, when fowls are confined to
the houses, and when there is a large number of birds per unit of floor
space.
A house should be regularly cleaned and disinfected in the thorough
manner described later, not less than twice each year and at such other
times as it may become empty. Trash, such as loose boards and empty
feed sacks, should not be allowed to accumulate in or around poultry
houses. The cleaning of premises in preparation for disinfection, either
as a routine procedure or after an outbreak of an infectious disease, is
described in the section on disinfection.
SANITATION OF POULTRY YARDS
Soil upon which chickens are kept always constitutes the most difficult
problem in poultry sanitation. Many types of disease germs discharged
with the excretions of infected birds find in soil a suitable medium for
their preservation until they may be taken up again by other chickens.
Soil, once infected, may remain so for varying lengths of time, according
to the nature of the infection, the character of the soil, and the conditions
of weather or climate. Left unpopulated, the infection in the soil will
gradually die out, but for some types of infection the time required for
this to occur is greater than any normal period of disuse of a yard on a
poultry farm. Therefore, even the practice of leaving brooder yards idle
12 University of California — Experiment Station
from one brooding season to the next or the rotation in use of yards is
likely to be inadequate for purification of contaminated soil. Disinfec-
tion of soil by means of chemicals is, as a rule, of uncertain value. A better
treatment, and one which may remove enough of the contamination to
make it worth the effort, is to sweep up and haul away the surface dirt
and accumulated droppings, particularly from the portion of the yard
adjacent to the houses.
Certain diseases, such as coccidiosis and intestinal worm infestation,
are so widespread that few poultry farms have escaped their ravages.
As time goes on, soil contamination is likely to build up, make control
of those diseases more difficult, and losses greater.
Such experiences have persuaded poultrymen to try raising their
chickens without direct contact with soil as a means of protecting them
from soil-borne diseases. The procedure has proved to be of much benefit
and also satisfactory from a husbandry standpoint. Both field experi-
ence and experimentation have clearly demonstrated that chickens do
not obtain any nutrient from soil or crops growing in the yards which
cannot be supplied in the feed, and that exposure to sunshine is the chief
if not the only benefit which chickens derive from being out of doors.
Consequently, small yards, surfaced with concrete or asphalt, or sun
porches, with the tops, bottoms, and sides made of wire netting, have
replaced soil yards on a large number of farms. From a sanitation aspect,
the sun porches are preferable. Usage has shown that the hard-surfaced
yards are difficult to keep clean unless covered with litter, and in warm
weather they become so hot that the chickens do not use them.
These substitutes for soil yards will not entirely eliminate soil-borne
diseases and parasites, and unless proper attention is given to their
cleanliness and sanitation, their benefit may be lost. They will, however,
reduce the likelihood of extensive outbreaks of such diseases, make it
easier to control any that do occur, and progressively reduce the prob-
lem. Therefore, raising chickens without direct contact with soil from
birth through the first laying year and even after, if desired, is highly
recommended.
DISINFECTION AND DISINFECTANTS 8
Disinfection means the act of destroying the cause of infection and
is based on our knowledge of the existence of disease germs. These germs
are extremely small and may remain for an indefinite time in dust,
cracks, and crevices, and in small particles of manure or other material
8 For additional information on disinfection, see :
Pope, George W. The disinfection of stables. U. S. Dept. Agr. Farmers' Bui.
954:1-12.1932.
Bonnikson, H. P. Disinfection of dairy stables. California State Dept. Agr. Mo.
Bui. 19 (5): 352-55. 1930.
Bul. 674] Diseases of Chickens 13
that may stick to the floor, to the walls of buildings, or to feed troughs
or other accessories. Efforts to remove and destroy them must, therefore,
be exceedingly thorough to be effective.
Direct Sunlight. — Sunlight is a natural agency that will destroy or
weaken the infective properties of some viruses and bacteria and the
eggs of many parasitic worms. Thus the value of placing the openings
in poultry houses to permit the entrance of as much sunlight as possible
is evident. Sunlight, however, cannot be regarded as more than an acces-
sory to other means of destroying disease germs.
Heat . — Heat is one of the most effective and most used disinfectants
available, but the possibilities for its application to poultry-house disin-
fection are limited. Some of the ways in which it may be utilized are as
follows :
Very hot water is destructive to bacteria and, where available direct
from a pipe line, can be utilized both for cleaning and disinfection.
When it is practicable to equip poultry houses with a hot-water line
from a steam boiler, the problem of cleaning and disinfection is greatly
simplified.
A jet of live steam can be utilized for disinfection when available.
Steam is ineffective a few inches away from the nozzle, however, and the
nozzle must be held close to the object against which it is directed and
moved slowly and systematically about until the entire surface has been
touched and heated to a boiling temperature. Merely filling a room with
steam is valueless.
Heat can also be applied by means of a "fire gun" (a large blowtorch)
to concrete floors and, to a more limited extent, to other parts of build-
ings and metal accessories. Its use should be restricted to types of build-
ings in which it would not create a fire hazard, to concrete yards, metal
feed hoppers, metal water vessels, and similar pieces of equipment. Al-
though the flame itself is intensely hot, a comparatively long exposure
must be given to raise the temperature of an object or surface to be
disinfected high enough to destroy all bacteria present. To be effective,
the flame should be moved very slowly and systematically over the entire
surface of the floor or equipment being treated. Stafseth of the Michigan
Agricultural Experiment Station has estimated that the disinfection of
concrete floors with this apparatus would require 1 hour for each 180
square feet (approximately) of floor area. The fire gun can be used
advantageously as an adjunct to chemical disinfection for burning up
particles of litter or droppings not removed by the cleaning process. Its
use on soil is of doubtful value because it cannot be relied upon to raise
the temperature of the soil sufficiently to such a depth as to make the
effort worth while.
14 University of California — Experiment Station
A steam sterilizer of the type used for milking equipment on dairy
farms can also be adapted to poultry farms for sterilizing accessories
and equipment, such as feed hoppers, drinking vessels, feeding buckets,
and nests. Gas or electric heating units can be obtained separately and
a sterilizer cabinet can be built from galvanized metal to any size and
shape desired. This is perhaps the most practical and effective means
of utilizing heat for disinfection on poultry farms.
Disinfecting with Chemicals. 9 — Certain chemicals which have the
power to destroy disease germs must be depended upon for the most part
in the practical work of disinfection. The selection of suitable and de-
pendable disinfectants is no easy matter. They vary greatly in character
and in their fitness for the purpose in view. An ideal disinfectant would
be: (1) highly effective against a large variety of germs; (2) highly
soluble in hard as well as soft water ; (3) retentive of germicidal action
after the exposure to air and contact with organic matter that occurs
when it is applied; (4) relatively nonpoisonous to man and farm animals;
(5) nondestructive of metals and fabrics; (6) of such composition that
it does not leave an objectionable residue or odor; (7) reasonable in
cost. Not all of these properties will be found in any one chemical disin-
fectant. Therefore, in selecting one for a particular purpose, the objec-
tionable features as well as the germ-destroying power of the preparation
must be given consideration. For example, a disinfectant which leaves
an oily residue might be satisfactory for a poultry house but not suitable
for an incubator or incubator room.
Disinfectants of similar composition are sold under a variety of trade
names. Before purchasing an unfamiliar brand, one should carefully
examine the label and make comparisons with some well-known product
of the same type. The "phenol coefficient" usually given on the label
is a fair, although not entirely satisfactory, means of comparison. To
protect the buyer against inferior products, federal and state laws re-
quire that the labels of disinfectants shall contain no statement, design,
or device which is false, fraudulent, or misleading in any particular.
Samples of commercial disinfectants are collected and tested, and when
evidence of adulteration or mislabeling is found, proper legal action
is instituted. These laws have less control, however, over statements
9 Some of the materials mentioned in this bulletin may become scarce or unavail-
able for civilian use because of the war. Where two or more chemicals are effective
in the prevention, control, or treatment of a disease, all have been mentioned. If
the reader finds that none of these are available now, he will naturally do the best
he can with any substitutes he can obtain. Great caution should, however, be exer-
cised in the use of substitutes, particularly those untested for the proposed service.
When in doubt about the advisability of using certain materials as substitutes for
those recommended, readers should consult the farm advisors in their respective
counties or the Agricultural Extension Service, University of California, Berkeley,
California.
Bul. 674] Diseases of Chickens 15
made by salesmen, by radio, or other advertising matter. Buyers, there-
fore, should accept only those statements of the worth of disinfectants
that are given on the label of the original container. Good guides in the
selection of a disinfectant for general farm use are lists of the products
tested and approved by the United States Bureau of Animal Industry
and by the Division of Animal Industry of the California State Depart-
ment of Agriculture for use in official disinfection. 10 The label on the
container of a product which has been given such official approval will
usually give a statement to that effect. A disinfectant should be diluted
according to the directions given on the label.
Details of Disinfection. — In order for a chemical disinfectant to kill
germs, it must come in close contact with them. If germs are protected by
a film of grease or albuminous matter or embedded in bits of dry manure
or dirt, the contact of the disinfectant with them is prevented and the
germs escape destruction. Furthermore, germs are very tiny and a small
bit of the discharges from diseased fowls or of other material can harbor
millions of them. This means that surfaces to be disinfected must be me-
chanically cleaned before action from the disinfectant can be expected.
All the nests, feed troughs, hoppers, and other accessories should be
emptied and brushed out. All of the surfaces, such as ceilings, walls,
partitions, floors, and droppings boards, should be swept until free from
cobwebs and dust. All litter, manure, and refuse from houses and yards
should be removed to a considerable distance and, in the case of a cleanup
after a disease outbreak, be burned if possible. After sweeping and
scraping as thoroughly as possible, the dried pieces of manure or dirt
that are still stuck to the floor or walls should be scrubbed off. For this
purpose a hot lye solution (see p. 18) is recommended. The building is
now ready for disinfection.
The best method of applying disinfectant is with a strong spray
pump. A high-pressure power-operated orchard spraying outfit is rec-
ommended. It is well to have the pump equipped with not less than 15
feet of hose, to which is attached a 5-foot length of iron pipe with a spray
nozzle at the end. With such equipment the operator can proceed rapidly
and reach all parts and surfaces easily. The disinfectant will have
greater effectiveness if applied hot. It is advisable for the operator to
wear rubber boots, heavy rubber or leather gloves, a wide-brimmed felt
or rubber hat, long-sleeved work clothing or a rubber coat. Equipped
10 The disinfectants recognized for official use are listed in : Permitted disinfect-
ants. U. S. Bur. Anim. Indus. Cir. Letter 2010. This may be obtained by writing to
the U. S. Bureau of Animal Industry, Washington, D. C,
A list of the disinfectants offered for sale within the state, with their analyses,
can be obtained from the Division of Chemistry, State Department of Agriculture,
Sacramento, California.
16 University of California — Experiment Station
in this manner, he can do a thorough job without any great danger of
the disinfectant's coming in contact with his skin.
The time element is an important factor in the effectiveness of disin-
fectants. For example, a disinfectant in the concentration used may kill
bacteria in 10 minutes but not in 5 minutes, or may kill certain types
of bacteria in 5 minutes and others in not less than 10 minutes. To ensure
an effective job, therefore, all surfaces and crevices must be so heavily
saturated with the disinfectant that they will remain wet for a consider-
able time. Care must be taken that the more inaccessible places, such as
the bottom surfaces of droppings boards and the interior and bottoms
of nests, feed hoppers, and other attached fixtures, are not neglected.
The characteristics and uses of some of the common disinfectants are
given on the following pages.
Phenol, or Carbolic Acid. — Phenol, a well-known coal-tar derivative
with a characteristic odor familiar to everyone, is a solid in the pure
state and, therefore, is usually sold in water solutions. It is a good dis-
infectant in 2 per cent to 5 per cent solution but is too expensive for
general use. It is rather caustic and must be carefully handled. "Phenol
coefficients" of other disinfectants are obtained by a standard procedure
of comparing their germicidal activity with that of phenol.
Cresol, or Cresylic Acid. — Cresol is a yellow or brown liquid deriva-
tive of coal-tar, with high disinfectant activity. Since it is only slightly
soluble in water, it is seldom used in the pure state, but is the active prin-
ciple of many of the best brands of commercial disinfectants.
Crude Carbolic Acid. — Crude carbolic acid should not be confused
with pure carbolic acid (phenol) or with cresol. It consists of a mixture
of phenol, cresol, and other coal-tar derivatives which are inert. Since
it is of uncertain composition and of low solubility in water, it is not a
satisfactory disinfectant. It may be used as a substitute for oil in spray-
ing a poultry house for the control of mites and ticks.
Saponified Cresol Solutions. — Water-soluble preparations consisting
of mixtures of cresol or cresylic acid and soap are called saponified cresol
solutions. They are very stable and efficient preparations and are used
extensively for official disinfection. The most refined preparation of
this type, Saponated Solution of Cresol U.S. P. is rather expensive and,
therefore, the cheaper substitutes are used for general farm disin-
fection. The United States Bureau of Animal Industry specifies that
saponified cresol solutions applied under its supervision must contain
not less than 50 nor more than 53 per cent cresol and not less than 21
per cent soap ; must form clear solutions in water and be used in the
proportion of 4 fluid ounces per gallon of water. Poultrymen should
purchase only saponified cresol solutions that meet these specifications.
Bul. 674] Diseases of Chickens 17
Sheep-Dips. — The coal-tar disinfectants known as sheep-dips form
milky solutions in water and vary greatly in their solubility and dis-
infecting value. For most purposes on poultry farms, they are less de-
sirable than saponified cresol solutions.
Chlorine Disinfectants. — Chlorine disinfectants are powdered or solu-
tions of hypochlorites prepared with chlorine gas. They are sold under
a great many trade names. Their value is dependent upon their content
of available chlorine, which should be at least 2.6 per cent by weight.
These preparations, although highly destructive to bacteria, are not
regarded as desirable for general disinfection because chlorine becomes
inactive in the presence of organic matter. Chlorine disinfectants are
very useful, however, for the disinfection of water supplies, or of water
troughs or fountains, feed hoppers, or other equipment with which the
use of a preparation of cresol might be objectionable. They should be
used according to directions on the container.
Chlorine gas has not been found of value for disinfection of poultry
quarters by fumigation or in the treatment of flocks for a respiratory
disease.
Iodine. — Iodine, a highly effective disinfectant, is adapted for use
on poultry houses and equipment only in a colloidal form called "iodine
suspensoid." This has been reported by the Michigan Agricultural Ex-
periment Station to be very destructive not only to bacteria but also
to coccidia and worm eggs which are strongly resistant to other disin-
fectants. For this reason, iodine suspensoid is recommended by the
manufacturer 11 particularly for disinfecting brooder-house floors and
equipment. Like chlorine, its action is quickly lost in the presence of
organic matter and therefore it should be applied only to surfaces after
they have been thoroughly washed.
Chlorinated Lime {Chloride of Lime). — Chlorinated lime, prepared
by saturating slaked lime with chlorine gas, is used principally as a
bleaching powder or as a deodorant. It should contain from 30 to 35
per cent of available chlorine. The United States Bureau of Animal
Industry recognizes chlorinated lime containing at least 30 per cent
available chlorine for official disinfection when used in proportions of
1 pound to 3 gallons of water. Products containing less available chlorine
should be used in more concentrated solutions. Fresh solutions must
be prepared daily. All products containing chlorine must be handled
with care, for chlorine is destructive to fabrics, leather, and metal.
Quicklime {Unslaked Lime, Calcium Oxide). — A fairly good germi-
cide, quicklime may be applied with a brush or spray as whitewash. It
is not recommended except to lighten the interior of dark poultry houses
11 Merck & Co., Inc.
18 University of California — Experiment Station
or as a covering for rough lumber. Its disinfectant action may be in-
creased by the addition of chlorinated lime or saponified cresol solution.
Since quicklime is very caustic, it must be handled carefully and poultry
kept away until whitewashed surfaces are thoroughly dry.
Slaked lime has no disinfectant properties.
Lye (Sodium Hydroxide) . — A 2 per cent solution of lye is an excel-
lent disinfectant ; in fact, it is more active against some disease germs
than saponified cresol solutions. It is also an excellent cleaning agent.
The use of a 2 per cent solution in hot water (1 pound to Q 1 /^ gallons or
one 13-ounce can to 5 gallons) is recommended for cleaning and dis-
infecting poultry houses. Since it is very caustic, users should wear
rubber boots and loose-fitting rubber gloves, be careful not to get any
on their clothing or skin, and have with them some vinegar for imme-
diate application to any portion of the skin with which the lye solution
may come in contact.
Copper Sulfate (Bluest one) . — Although copper sulfate and some
other copper salts are very destructive to algae and some fungi, they
are much less destructive to bacteria, and, consequently, they are not
considered as good general disinfectants. The usefulness of copper sul-
fate, therefore, is limited to treatment of drinking water and for clean-
ing water vessels and areas around them in combatting fungus diseases.
Drinking water containing more copper sulfate than 1 part in 500 may
be toxic to birds and also may make the water so distasteful that con-
sumption is seriously reduced.
Potassium Permanganate. — Potassium permanganate, although hav-
ing no usefulness as a general disinfectant and no medicinal value, is
convenient and safe for use as an antiseptic in drinking water, is inex-
pensive, and relatively nonpoisonous to poultry. One level teaspoon in
each gallon of drinking water will aid in preventing the spread of infec-
tion by the water. When the solution loses its germicidal property, its
color changes from purple to brown, and it should then be renewed.
Bichloride of Mercury (Corrosive Sublimate) . — Bichloride of mer-
cury is a powerful disinfectant in a 1 to 1,000 solution in water. It is
usually dispensed in tablet form and with directions stating the amount
of water in which one tablet should be dissolved to make a solution
having the desired strength. It has the disadvantages of being a violent
poison, of corroding metals, and of uniting with albuminous substances
to form inert compounds. Unlike the disinfectants previously described,
corrosive sublimate leaves no odor and on this account is useful where
odors would be undesirable. It must be handled with great caution to
avoid accidental poisoning of stock, dogs, or cats, and the solutions
must be prepared in wooden or earthenware containers. Water or feed
Bul. 674] Diseases of Chickens 19
troughs to which it has been applied should be washed with fresh water
before they are used again.
Sodium Orthophenylphenate. — This substance has only recently been
recommended as a general disinfectant. It has no objectionable odor,
is relatively nontoxic, is highly efficient for most disease germs, and is
readily soluble in water. It may be purchased in the form of a grayish,
brownish, or white powder or flakes, which must be kept in a closed
container to prevent deterioration. It is now sold under several trade
names, which are included under the United States Bureau of Animal
Industry list of permitted disinfectants. It gives best results when ap-
plied hot.
Formalin and Formaldehyde Gas. — Formaldehyde gas is an excellent
disinfectant available through usual trade channels as formalin, a watery
solution containing not less than 37 per cent of the gas. The latter has
high germicidal properties in 5 to 10 per cent solution, but is objection-
able for use as a general disinfectant because the fumes which it gives
off are very irritating to the eyes and nose. It is relatively nonpoisonous
to animals, does not harm metals or fabrics, and leaves no residue or
lasting odor. It is useful, therefore, in the disinfection of water vessels,
feed hoppers, and other poultry-house accessories.
Formalin finds its principal use as a source of formaldehyde gas for
disinfection by fumigation of any building that can be made nearly
airtight. Few, if any, poultry houses, however, can meet this require-
ment. Fumigation in a small, tightly closed room would be practicable
for clothing and other equipment that are difficult to disinfect by other
methods. The usual means for liberating formaldehyde gas is by the
chemical reaction that occurs when formalin is mixed with potassium
permanganate. The procedure is as follows :
For each 1,000 cubic feet of air space, 16% ounces of potassium permanganate
crystals or powder is placed in a wide pan; 20 ounces of formalin is then poured
upon it and the room immediately closed for 12 hours or longer. Since considerable
heat is generated by the chemical reaction, it is well to place the pan containing
the chemicals in a larger pan containing water. The temperature in the room should
not be less than 65° F and the humidity not less than 60 per cent.
At present, formaldehyde gas is used rather extensively for the dis-
infection of incubators of the forced-draft type. Fumigation is not so
well adapted to the compartment, or still-air, type of incubator except
between hatches because of the slowness with which the gas would
escape from a compartment. Fumigation of forced-draft incubators is
said to be safe between hatches, while eggs are in the incubator, and even
when chickens are hatching out. This is neither a safe nor a successful
practice unless a correct procedure is exactly followed. It is best to
20 University of California — Experiment Station
follow instructions obtained from the manufacturer of the incubator
to be disinfected.
The directions for two methods of incubator fumigation based on
Ohio Agricultural Extension Bulletin 90 12 and Illinois Agricultural Ex-
periment Station Circular 403, 13 are as follows :
Potassium permanganate method : 1. For each 100 cubic feet of in-
cubator space, use 70 cc of formalin and 35 grams of potassium perman-
ganate if the fumigation is done between hatches or on the seventeenth
or eighteenth day of incubation. Use only one half of the above amounts
of chemicals if the incubator is fumigated when chicks are hatching.
2. Place the potassium permanganate in an enamelware pan (never
in a glass or pottery container) that holds at least ten times the amount
of chemicals used, and put this in the control compartment of the in-
cubator below the fan. More than one pan may be necessary for large
incubators.
3. Pour the formalin over the potassium permanganate and close the
incubator door at once. Leave the door closed for 3 hours. No change in
the ventilation of the incubator is necessary.
The cheesecloth method : 1. Measure out 40 cc of formalin for each
100 cubic feet of incubator space. Use only one half of this amount if
the incubator is fumigated while chicks are hatching.
2. Cut a piece of cheesecloth large enough to absorb all of the formalin
(1% yards for each 100 cc).
3. Completely absorb the formalin with the cheesecloth and hang it
under the fan in the incubator. For large incubators, hang a strip of
cheesecloth under each fan. Close the door and start the fan. Do not
open the door for 3 hours. No change in the ventilation of the incubator
is necessary.
Fumigation of incubators while chicks are hatching is a somewhat
hazardous procedure. If it is done, the cubic content of the incubator
should be very accurately computed and the correct amount of formalin
carefully measured out. Never fumigate chicks more than 48 hours old.
With the potassium permanganate method, make one fumigation
when 5 to 10 per cent of the chicks are out of the shell and two more,
12 hours apart. Three or 4 hours after each fumigation, remove all
chicks that are dry.
With the cheesecloth method, fumigate twice, once when from 10 to
20 per cent of the eggs are hatched and again 12 to 15 hours later. Three
or 4 hours after each fumigation, remove all dry chicks.
12 Dakan, E. L., and Fred Speer. Sanitation in the hatchery. Ohio Agr. Ext. Bui.
90:1-16.1929.
13 Graham, Robert, and V. M. Michael. Incubator hygiene in the control of pullorum
disease. Illinois Agr. Exp. Sta. Cir. 403:1-16. 1933.
Bul. 674] Diseases of Chickens 21
During fumigation by either method, the incubator temperature
should be 90° to 100° F and the wet-bulb thermometer reading, 90°
to 95°.
Paraffin-Oil Emulsion. — Paraffin-oil emulsion is a very effective spray
for killing ticks, mites, and certain other external parasites which hide
in the cracks and crevices of poultry houses during at least part of their
lives. It is prepared by first dissolving 1 pound of soap in 10 quarts of hot
water. After the soap has dissolved, the solution is removed from the fire
and allowed to cool to a lukewarm temperature. Then 10 quarts of paraf-
fin oil are added to the soap solution and thoroughly stirred until the
liquid becomes creamy. This constitutes the stock solution. The spray
is made by diluting 1 part of the stock solution with 6y 3 parts of water.
Lime-Sulfur Dip. — Lime-sulfur dip is employed in the control of cer-
tain external parasites, as described in the section of this publication
dealing with parasitic diseases. It may be made up at home by using
8 pounds of quicklime and 24 pounds of flowers of sulfur to 100 gallons
of water. The lime is slaked with sufficient water to form a thick paste
and the sulfur is then sifted in and mixed thoroughly with a hoe. This
mixture is placed in a kettle with 30 gallons of water and boiled for 2
hours. Prepared "lime-sulfur" dips can be purchased on the market
and should be used according to the directions given on the container.
Kerosene Emulsion. — Kerosene-emulsion oil spray is sometimes used,
as described later in the section dealing with external parasites, to con-
trol certain species of poultry pests. It is made by first dissolving %
pound of soap in 1 gallon of hot water ; if the water to be used is hard,
a little borax should be added to soften it. After the soap is dissolved,
the solution is taken from the fire and allowed to cool. Then 2 gallons of
kerosene are added and, with a small hand spray pump having a fine
nozzle, the mixture is drawn into the pump and out through the nozzle
back into the container from which it was drawn until it becomes so
thick as to go hard through the pump. This stock solution is diluted with
5 parts of water to make the finished spray. The stock solution, if well
prepared, should keep for at least a month.
Wet table Sulfur. — Finely ground sulfur to which has been added a
material which will increase its suspensibility in water is called "wettable
sulfur." Commercial preparations are readily available.
Creolin. — Creolin is a mixture of high-boiling coal-tar oils and phenols
rendered emulsifiable with water by a special process. Creolin (veter-
inary) is employed in the control of certain external parasites of poultry.
Anthracene Oil. — Anthracene oil, a coal-tar oil that is heavier than
creosote, sometimes known as "carbolineum," is effective in controlling
ticks and mites in poultry houses.
22 University of California — Experiment Station
MANAGEMENT PRACTICES IN PRE VENTING AND CONTROLLING
TRANSMISSIBLE DISEASES
The discussion of prevention and control of disease thus far has been
concerned principally with the elimination of the spread of infection
through contaminated material in houses and equipment by cleanliness
and disinfection. Consideration will now be given to practices of a
different nature which are necessary for the elimination of some of the
other and equally dangerous means by which infection may be intro-
duced to or spread about a farm. Failure to put these practices into
operation may nullify the benefit from a carefully conducted program
of cleaning and disinfection.
Infection may be spread by anything, living or inanimate, which may
pass, by design or chance, from one poultry farm to another or between
different pens of chickens on the same farm. Some of these, such as wild
birds and dust carried by the wind, are wholly or partially uncontrol-
lable, but this is not true of chickens added to a flock, poultry crates,
visitors, poultry buyers, and many others. Some of the precautionary
measures that may be adopted to prevent the spread of disease by such
agencies are given in the following paragraphs.
Measures to Prevent Introduction of Infection to a Farm. — 1. For the
establishment of new flocks or in making additions to existing ones,
hatching eggs or day-old chicks are not likely to introduce any infection
except pullorum disease or similar infections which may be transmitted
through eggs, and this can usually be avoided by a careful investigation
of the source of the chicks (see p. 26-38).
2. Partly grown or mature chickens, including breeding males or
females, should not be used to establish a new flock or be added to an
existing flock unless one can be certain that they have not been exposed
to or affected with some infection which they may still be carrying. It
is possible for such chickens, although apparently healthy, to carry in-
fective material mechanically on feathers, feet, or other parts of the
body; to be in the incubation stage of a disease to which they have re-
cently been exposed during transit or while exhibited at shows or fairs,
or to be healthy carriers of disease, that is, to still carry the causative
agent of a disease, such as infectious coryza, infectious laryngotracheitis,
or fowl cholera, with which they had been infected and apparently re-
covered. The last of these has been the more common means by which
disease has been brought to a farm by seemingly healthy chickens. Pur-
chase of chickens under a guarantee of freedom from a transmissible
disease is not necessarily good insurance because the seller may not have
a clear understanding of the disease condition in his flock. For example,
Bul. 674] Diseases of Chickens 23
he may have a mild form of infectious coryza (cold) in his flock and
regard this as a harmless type of cold or may have had an outbreak of
infectious laryngotracheitis in the flock and not know that recovered
chickens may carry the virus of this disease indefinitely.
3. If partly grown or mature chickens are purchased, they should be
kept separated from other chickens for at least 2 weeks to allow for the
development of any acute disease with which they may recently have
been infected. The same applies to chickens returned from a show, fair,
or contest. This precaution, however, is not adequate to reveal the pres-
ence of healthy carriers among the new chickens.
When a small group of new breeding birds is brought onto a poultry
farm, the safest procedure is to keep the new birds permanently isolated
and add their progeny, instead of the new birds themselves, to the flock.
4. Breeding chickens should be purchased subject to a negative re-
action to the test for pullorum disease unless they come from a flock
which, by having been systematically tested over a period of years, has
been shown to be free from this disease. Chickens from a pullorum-
disease-free flock which have been entered in a show or contest should
be tested for pullorum disease before they are returned to the flock.
5. Visitors, particularly those whose business or occupation takes them
from farm to farm, should not be permitted to enter poultry houses or
yards.
6. Poultry buyers' crates should not be allowed on a poultry farm
unless they have been thoroughly cleaned and disinfected since last
used, and even then had best be kept outside of the houses and yards.
The poultry buyers should likewise be excluded from the houses. Crates
belonging on the farm should be cleaned and disinfected each time they
are used for taking chickens to market.
7. All openings in the walls of the houses, except doors and chicken
exits, should be covered with wire netting of a mesh small enough to
exclude wild birds. The possibility of infection being introduced by
wild birds can be further reduced by the use of wire mesh-covered sun
porches instead of open yards.
8. Areas of a farm on which poultry houses are located should be well
fenced to prevent chickens from escaping to neighboring farms, from
which they might bring back disease, and also to keep out chickens
which may stray from neighboring flocks.
9. Measures to keep down flies and mosquitoes should be adopted.
This may require not simply the proper disposal of manure and the
elimination of breeding places of mosquitoes by the individual poultry-
man but also community action and the establishment of mosquito-
abatement districts.
24 University of California — Experiment Station
Measures to Prevent 'the Spread and Recurrence of Disease on a
Farm. — The recommendations which follow are of particular impor-
tance as aids in preventing the recurrence of certain diseases among
the growing stock and laying pullets on a farm each year. Some of these
are perpetuated by contaminated houses, yards, and equipment; others
by cases of latent infection or healthy carriers among the older chickens
which have been infected previously.
1. All houses and equipment should be thoroughly cleaned and dis-
infected before they are used for young chickens.
2. Land should not be used for a pullet range if it has been recently
occupied by adult chickens or is close to pens of adult chickens.
3. Pullets not raised on range should be confined to houses and wire-
mesh sun porches. The litter in the houses should be renewed at least
once a week until the end of the first laying year.
4. Pullets should be housed entirely separate from older birds. Empty
sections of a house partially filled with adults should not be used for
pullets.
5. On large farms, separate attendants and equipment for pullets and
for adult birds should be provided.
6. If indications are seen of a disease against which sanitation is par-
ticularly effective, precautionary measures should be increased by such
means as more frequent renewal of litter, more thorough and frequent
cleaning and disinfection of water and feed containers, and careful in-
spection of the flock for the purpose of detection and removal of sick
birds.
7. Any chickens that become sick should be immediately taken out of
the flock and either isolated for further observation or killed and burned.
By the prompt isolation of the first cases of an infectious disease, a
serious outbreak may be headed off. If several cases of an unknown
disease occur, specimens should be taken or sent to a veterinarian or to
the nearest of the laboratories of the State Department of Agriculture
or of the University for examination. 14 Do not rely upon diagnoses made
14 The State Department of Agriculture laboratories are located as follows : State
Office Building, Sacramento; 627 F Street, Petaluma; and 1451 Mirasol Street, Los
Angeles. The University of California laboratories are in the Division of Veterinary
Science at Berkeley and Davis.
In shipping specimens the sender should : (1) Be certain that the specimens selected
are representative of the major illness in the flock. (2) Send sick rather than dead
chickens if a selection of representative specimens can be made on the basis of
symptoms. (3) Select dead chickens as soon after death as possible, thoroughly
chill them in a refrigerator or by other means and wrap them in several layers of
paper. (4) Ship by prepaid express. (5) Take the specimens to the express office
just prior to the departure of a train that will ensure delivery to the person making
the examination on the same day as shipped or in the morning after an overnight
journey. (6) Attach to the package in a sealed stamped envelope a statement telling
Bul. 674] Diseases of Chickens 25
by remedy or feed salesmen, or servicemen, or other persons untrained
in the diagnosis of poultry diseases!
8. If an outbreak of an infectious disease occurs in a flock, the still
healthy chickens should be moved to clean pens. New cases that develop
should be immediately taken out. The detection of new cases will be
facilitated by dividing the flock into as many small groups as possible.
All sick chickens should be killed and the carcasses burned ; the houses,
feed and water containers, and other equipment, should be thoroughly
cleaned and disinfected. Yards should be cleaned and plowed and left
idle for a month or more. The safety of the houses and yards for re-use
may be determined by keeping a few young test chickens in them for a
month before they are fully restocked.
Medication of Drinking Water. — Nonpoisonous chemical disinfect-
ants may be added to the drinking water for flocks when an infectious
disease occurs. The only benefit of this practice results from the ability
of the disinfectant to destroy disease germs in the water and thus pre-
vent disease from spreading by this medium. Contrary to common belief,
such chemicals do not act as intestinal disinfectants nor otherwise exert
a beneficial action after consumption by the fowls.
Chemicals for disinfection commonly used in the drinking water are
potassium permanganate or one containing chlorine. The amount of the
former to add is that sufficient to give a claret color to the water. More
should be added when the color fades. The amount of a chlorine com-
pound to add is determined by its content of available chlorine (as
given on the label). An amount sufficient to provide 1 part of available
chlorine in 3,000 parts of water may be used with safety. Dilutions of
chlorine as high as 1 part in 100,000 will destroy germs but are not
suitable for use in the poultry house because of the rapidity with which
chlorine is inactivated in the presence of organic matter.
Copper sulfate in the drinking water has a limited usefulness as an
aid in the control of certain fungus diseases (see p. 98).
Medication of the Feed. — Some nicotine preparations and possibly
certain other chemicals that are used to treat chickens for intestinal
worms may be adminstered mixed with the mash. Otherwise, no sound
evidence of benefit from medicated mashes has been shown.
The combination of drugs known as "tonics" for mixing with the
poultry feed have little, if any, value in preventing or curing infectious
diseases. Possibly they may serve to stimulate the appetite of convalese-
the age of the chickens affected, the size of the flock, the number already affected,
symptoms shown by the sick, whether the same or similar condition has previously
existed on the farm and other pertinent information. (7) Give the name and address
of both owner and sender, if shipment is not made by the owner.
26 University of California — Experiment Station
ing flocks and thereby hasten return of the fowls to normal condition. A
formula that may be used is as follows :
Pulverized gentian 1 pound
Pulverized ginger *4 pound
Pulverized saltpeter % pound
Pulverized iron sulfate % pound
Pulverized nux vomica % pound
Add 1 ounce of the preparation to each 5 pounds of mash.
INFECTIOUS DISEASES
The diseases discussed in this section are limited to those that are of
particular economic importance to the commercial poultry industry of
California. Nearly all of those that occur sporadically and cause only
small losses, or that, although prevalent in some parts of the world, do
not occur in California, are omitted.
PULLORUM DISEASE (BACILLARY WHITE DIARRHEA)
Pullorum disease is caused by infection with a species of bacteria
called Salmonella pullorum and affects both chicks and adult fowls.
Chicks have an acute form of the disease from which many succumb
after a brief illness. In adults the infection is usually localized in the
ovaries and rarely produces visible symptoms.
The term "white diarrhea" is a misnomer. Diarrhea is not a character-
istic or constant symptom of the disease in chicks and the frequently
occurring white chalky discharge from the vent of adults is seldom
related to pullorum infection.
Symptoms and Diagnosis of the Disease in Chicks. — Diseased chicks
do not exhibit any symptoms that are of particular diagnostic value. A
small amount of chalklike material may be seen adhering to the fluff
below the vent of many of the chicks, and occasionally such collections
around the vent attain considerable size. But, as stated previously, diar-
rhea is very often absent and is perhaps just as frequently seen accom-
panying conditions other than pullorum disease. A high mortality in a
flock of correctly brooded chicks during the first 2 weeks of their lives
strongly suggests pullorum disease but is not a definite indication of
it, since there are other causes of excessive mortality among young
chicks. According to some observations, an abrupt rise in the number
of deaths 6 to 8 days after hatching, followed by a considerably de-
creased yet abnormally high mortality up to 2 weeks of age, is more
suggestive of pullorum disease than a high mortality during the first
few days after hatching. Contrary to common belief, pullorum disease
in chicks does not always cause heavy mortality. Therefore, the disease
Bul. 674] Diseases of Chickens 27
may be present without exciting suspicion on the part of the caretaker
and thereby escape detection. An abnormally high mortality can be
expected if the brooding conditions for the infected flock are poor, the
diet is faulty, or the quality of the chicks is low.
The finding in dead chicks of yellow or ocher-colored livers and of
unabsorbed yolks was formerly considered indicative of pullorum dis-
ease. Such findings, however, are commonly seen in chicks that die
during the first week and are absent from those which die later, regard-
less of the cause of death. Furthermore, unabsorbed yolk is present in
many normal chicks under a week old.
More characteristic changes are found in chicks which die during the
second week. These consist of small gray spots in the liver, gray nodules
in the heart wall, and gray or yellowish nodules in the lungs. But even
these lesions are not sufficiently typical or constant in their occurrence
for certain identification of the disease. Consequently, a positive diag-
nosis of pullorum disease can be made only by bacteriological procedures
in a laboratory. These require at least 48 hours for completion.
Symptoms and Diagnosis of the Disease in Adults. — Pullorum disease
is present in many flocks of adult chickens, but only occasionally does
it cause an acute fatal type of disease. Probably some of the earlier
reported outbreaks of this nature were in reality due to some other
but closely related species of organisms, which, because of inadequate
bacteriological procedures, were not differentiated from Salmonella
pullorum.
Salmonella pullorum has been reported as causing an inflammation
of the oviduct of pullets, which was manifested by eggs with an offensive
odor, blood-spotted and blood-smeared eggs, soft-shelled eggs, a profuse
white discharge from the vent, and the practice of cannibalism. Occur-
rences of this nature from pullorum infection, however, are compara-
tively rare. The writers have examined numerous chickens with inflamed
oviducts and chalky discharge from the vent without being able to in-
criminate any organism as the causative factor.
Pullorum disease of adults usually becomes localized in some organ
where it remains dormant and produces no external evidence of its pres-
ence. In males, it has been found most frequently in the heart sac but
has been isolated also from the testes, spleen, gall bladder, and heart
muscle. In females, the ovary is the organ most frequently involved. The
prominent changes here are abnormal yolks (fig. 7). These abnormalities
include bloody and cheesy ovules; cysts attached to the ovary; small,
partially solidified blood-tinged yolks ; yolks of various sizes with cap-
sules but partially filled with thick yellow or greenish-yellow liquid;
solidified, angular, yellow, greenish-yellow, or blood-tinged yolks; and
28
University of California — Experiment Station
yolks with a thick opaque capsule containing yellow, semisolid, oily
material or a clear yellow, oily liquid with white flakes in suspension.
Caseous egg material in the oviduct is also a rather common location
of the organism.
Fig. 7. — Ovaries of a hen infected with pullorum disease : nos. 1 and 2 are
normal yolks ; nos. 3 to 9 and many of the smaller yolks are abnormal because
of the infection. Such abnormalities may also result from other causes. (From
Ext. Cir. 8.)
Localization of the infection may also occur in other and sometimes
very obscure places, particularly the heart sac, either in addition to or
in the absence of ovarian lesions. One case has been reported in which
it was isolated from the middle ear only, with no evidence of infection
Bul. 674] Diseases of Chickens 29
in any other part. As with chicks, the finding of characteristic lesions
on autopsy by no means definitely indicates the presence of infection,
and bacteriological examination must be resorted to in establishing a
diagnosis. A means of detecting pullorum disease in the living fowl is
afforded by the agglutination test, discussed later.
The Effect of the Disease on Production and Reproduction. — Pullo-
rum disease of adults, although usually localized and not responsible for
the death of many birds, causes serious loss by its effect on egg produc-
tion and reproduction. It has been established that infected fowls, as a
rule, lay fewer eggs than noninfected fowls of like quality. The most
serious consequence, however, is that living germs may be contained in
hatching eggs laid by an infected hen and thus be introduced into a
hatchery. When an infected fertile egg is incubated, the embryo becomes
infected and either dies in the shell or survives to emerge as an infected
chick, from which the infection spreads to other chicks in the incubator,
chick boxes, and brooder.
Infected chicks hatched from infected eggs are the source of the in-
fection responsible for most outbreaks among flocks of chicks. A single
infected chick among a batch at the time of hatching is sufficient to infect
many others before the chicks leave the incubator or after they are placed
in shipping boxes or in the brooder. In forced-draft incubators the in-
fection may be widely disseminated by means of down from the infected
chicks. With the still-air type of incubator, consisting of a series of
small compartments, the spread of infection within the incubator is
ordinarily confined to the compartment in which the infected chicks
are located. Incubator-acquired infection may enter the bodies of the
chicks by way of either the digestive or the respiratory tracts. Infection
by the latter route is probably responsible for the occurrence of lesions
in the lungs.
Other sources of infection in chicks are contaminated incubators,
shipping boxes, brooder houses, or brooding equipment, all of which can
readily be eliminated by the sanitary measures discussed on pages 7-25.
Variation in the Extent of the Infection among Progeny of Infected
Flocks. — Much variation has been observed in the occurrence of pul-
lorum disease among different hatches of chicks from flocks in which
there were presumably infected hens and even among different lots of
chicks of the same hatch that were shipped to different poultrymen.
Many breeders and hatcherymen and some investigators have, there-
fore, questioned whether the infected hen was really dangerous as a
source of infection among chicks. Consideration of some of the following
four facts regarding the infection in hens and its manner of dissemina-
tion affords explanation for variations of this nature.
30 University of California — Experiment Station
1. A wide variation has been shown to exist in the frequency of the
occurrence of infection in eggs laid by individual infected hens.
2. Many infected eggs fail to hatch because of infertility or death of
the embryo in the shell.
3. Many of the chicks that hatch from infected eggs die or are de-
stroyed soon after they emerge from the shell and before there has been
much opportunity for dissemination of infection among the healthy.
4. In the case of difference in the amount of the disease among several
lots of chicks from one large hatch, but a few of the chicks may have been
infected and all of these may have been contained in one or two lots.
It is, therefore, conceivable that even though a flock may contain
numerous infected hens, very few infected eggs may be produced, or
may hatch, and hence loss from pullorum disease may occur infrequently
or irregularly among the flock's offspring. It must be borne in mind, how-
ever, that exactly the reverse may occur. Numerous infected eggs may
be laid from which infected chicks may be hatched, and conditions may
be such that infection will be rapidly and widely disseminated among
the others of the hatch.
Sources of the Infection in Adults. — The majority of infected adults
are those which were infected as chicks and in which the bacteria became
localized in some organ as previously described. Fowls can, however,
acquire the infection and become carriers at any age. The practice of
feeding uncooked infertile and dead-germ eggs from the incubators has
produced extensive infection in some flocks. It has also been demon-
strated that healthy hens may acquire infection from association with
infected hens.
To what extent males may be responsible for the spread of infection
among hens is not clearly understood. The actual transmission of the
disease to hens by infected males has not been conclusively demon-
strated. Nevertheless, an infected male must be regarded as a potential
source of infection of hens with which he may be associated. There is
evidence that the infection will spread more rapidly among hens when
males are present in the flock than when only females are present. The
role of the male in this case is probably that of a mechanical carrier of
infection from hen to hen.
Control of Outbreaks of the Disease in Chicks. — There is little evi-
dence to indicate that efforts to reduce losses from outbreaks of pul-
lorum disease among chicks have, as a rule, been highly successful.
Many of the seemingly good results from methods that have been tried
are probably due to the fact that the mortality in outbreaks varies be-
tween wide limits and many times is low, and that the deaths usually
have greatly decreased or have entirely ceased by the time the chicks are
Bul. 674] Diseases of Chickens 31
from 2 to 3 weeks old. The employment of sanitary measures are un-
doubtedly of benefit if properly carried out. These would consist of
cleaning and disinfecting houses and equipment, promptly removing
and destroying sick or dead birds, and dividing the chicks into as small
units as possible. This last-mentioned measure might be highly effective
in preventing heavy losses if it were done early in the outbreak, if not
many infected birds were left in the flock after the visibly sick ones had
been removed, and if these were contained in one or two of the small
units.
In controlled experiments with artificially infected chicks, drugs and
chemicals, including potassium permanganate, hydrochloric acid, mer-
curic chloride, sulf ocarbolates, sulfuric acid, resorcin, and several hypo-
chlorite (chlorine) solutions, were shown to be of no benefit when taken
into the alimentary tract and, therefore, ineffective in reducing mortality
among chicks that were actually infected. Some chemicals, however,
particularly the hypochlorite solutions, may be of some value as disin-
fectants in drinking water to prevent the spread of infection through
this route. They should be used as directed on the container.
Prevention of the Disease. — As in other infectious diseases, successful
prevention lies in removing the sources of infection. These are, as pre-
viously stated, contaminated incubators, shipping boxes, and brooders;
also infected chicks, particularly before removal from the incubator,
and infected hens.
The incubators and brooders can readily be eliminated as sources of
infection by thorough cleaning and disinfection before each time they
are used, and the boxes by using only new ones or by disinfection after
each use.
In forced-draft incubators, as previously stated, infection may be
widely disseminated at hatching time on the down from diseased chicks.
This can be reasonably well overcome by fumigation with formaldehyde
gas (see p. 20) at suitable intervals during the incubation period and
while hatching is taking place. It is said that this procedure, if correctly
done, will not decrease the hatchability of the eggs or harm the chicks
and will prevent dissemination of the disease through the incubator by
destroying the infection on the down of chicks that have hatched from
infected eggs. This treatment, of course, does not destroy the organisms
within the bodies of the infected chicks and, therefore, they remain
sources of infection after they are taken from the incubator. Careful
inspection of the chicks for the purpose of detecting and removing those
that are weak will serve to remove many of the infected ones and will
accordingly reduce the likelihood of serious losses from pullorum disease
in the brooder.
32 University of California — Experiment Station
The elimination of infected breeding fowls, the most serious source
of pullorum disease in chicks, is a more difficult procedure because such
fowls, from outward appearance, cannot be distinguished from healthy
ones. The only practical means for the detection of pullorum disease
carriers that has thus far been discovered is a blood test, known as the
"agglutination test." This has been popularly termed the "B.W.D. test"
and has been used extensively for several years. Three methods of mak-
Fig. 8. — Method of drawing a blood sample for the agglutination test.
(From Ext. Cir. 8.)
ing the agglutination test have been developed : the slow serum, or tube,
test ; the rapid, or plate, serum test ; and the rapid whole-blood test. A
skin test, termed the "pullorin test" has also been tried. This test is
much easier to apply than the agglutination test, but the results ob-
tained with it have been unsatisfactory.
The Slow Serum Agglutination Test. — For the slow serum, or tube,
agglutination test, from IV2 to 3 cc of blood are obtained from each
fowl by puncturing the wing vein and collecting the blood in small
clean vials or test tubes (fig. 8). A number, corresponding to that on
the leg band of the fowl, is written on the cork or a gummed label on the
vial, which is then placed in a slanting position until the blood has
clotted. The vials are then placed in a cool place, preferably in a refrig-
erator, until the serum, or clear, straw-colored liquid portion of the
blood, has separated from the clot. In case the serum does not separate
Bul. 674] Diseases of Chickens 33
within a few hours, the clot is stirred with a toothpick and allowed
to stand a few hours longer. A minute quantity, usually from 0.01 to
0.04 cc, of the serum of each blood sample is mixed with a small amount
(usually 1 cc) of test fluid or antigen in a test tube. The antigen consists
of 0.85 per cent salt solution containing a small amount of phenol or
other preservative, to which has been added sufficient killed Salmonella
pullorum bacteria to make the liquid slightly cloudy. The serum-antigen
Fig. 9. — A positive (left) and negative (right)
reaction to the tube, or slow, agglutination test.
(From Ext. Cir. 8.)
mixture is allowed to stand for 24 hours or longer at incubator or room
temperature before a reading of the results of the test is made. If the
blood serum contains what is known as agglutinins, the organisms in
the antigen clump together and sink to the bottom of the tube with con-
sequent clearing of the fluid. This is known as a positive reaction (fig. 9) .
Most fowls with pullorum disease have agglutinins in their blood and
give a positive reaction to the agglutination test.
The Rapid Serum Agglutination Test. — The rapid serum agglutina-
tion test is made on a clean glass plate which is ruled into squares of
about 1 inch with a diamond-pointed or wax pencil. Blood serum is ob-
tained in the same manner as for the slow agglutination test. A small
amount (0.02 to 0.04 cc) of blood serum is transferred to a square on
the glass plate where it is mixed with a drop (0.04 to 0.05 cc) of antigen.
This antigen has a concentration of bacteria about fifty times that of
34 University of California — Experiment Station
the antigen for the slow agglutination test. The glass plate is placed
over a black background or used as a cover for a box, the interior of
which can be illuminated. The reaction, that is, clumping of the bacteria,
is completed and can be read in from 1 to 15 minutes (fig. 10) .
The results of comparisons of the rapid test with the slow test indicate
that the two are equally satisfactory in the detection of carriers of
Salmonella pullorum. The advantage of the rapid one is that extensive
laboratory facilities are not required and the test results are obtained
more quickly. Considerable experience is required, however, to interpret
the reactions correctly. Veterinarians or others undertaking this work
Fig. 10. — A positive (left) and negative
(right) reaction to the rapid serum aggluti-
nation test. (From Ext. Cir. 8.)
should first spend some time in a laboratory where experience in making
and reading tests can be obtained and should have an unquestionably
reliable source of good antigen.
The Rapid Whole-Blood Agglutination Test. — The whole-blood test
is made on a clean glass plate, ruled into 1- or 2-inch squares, which is
placed over a white background or used as a cover for a box, the interior
of which is painted white and can be illuminated. A testing box which
embodies the desirable features is shown in figure 11. Similar ones are
obtainable from producers of antigen or can be made at home. A white
porcelain plate as advocated by some is less satisfactory. A drop of fresh
blood, obtained by pricking the comb or wing veins, is transferred with
a wire loop 13 (or a medicine dropper) to a square on the plate and is
well mixed with the same volume of antigen. The antigen for this test
is deeply colored with a violet dye. The reaction or clumping of the
bacteria occurs within a few seconds to a few minutes (fig. 12). The
entire procedure is carried out on the poultry farm.
The fowls are held in individual coops, numbered to correspond to
squares on the glass plate in which the test is made. When the test is
15 The loop recommended is made % 6 inch in diameter at the end of a piece of
noncorrosive wire (Brown & Sharp, gauge no. 20). The loop can be made around
a no. 20 steel drill or a 10-penny nail. For convenience in handling, the wire is in-
serted into a wood or metal handle or a cork.
Bul. 674]
Diseases of Chickens
35
completed, the fowls are retained for disposal if the reaction is positive
or returned to the flock if the reaction is negative.
Some of the requirements for getting maximum efficiency are as
follows :
1. The blood and antigen should be thoroughly mixed and spread over
an area about 1 inch in diameter immediately after the blood is added.
Fig. 11. — Box for making whole-blood agglutination tests. Capacity of the
box is 5 glass plates, or 50 tests within the incubation chamber, and 2 glass
plates, or 20 tests on the outside shelf. A thermometer should be attached to
the side of the incubation chamber just beneath the test plates. The dimensions
&Te: AB 14% inches DE % inch
BC 13 inches FG 9% inches
CD 5y 2 inches GH 3 finches
EFG, Hinged cover for incubation chamber. It protects against dust and
prevents excessive evaporation.
GUI, Shelf holding two 1% X l^ r A inch glass test plates. Each plate contains
ten l^-inch squares and is set y± inch above the metal cover of the chamber con-
taining the lights. As soon as a test has been started in each square, the plate
can be slid into the incubation chamber without raising the cover.
Compartment GRAB contains two 50-watt lights and is separated from the
incubation chamber by a removable glass panel at the point G. A switch at J
permits turning the light off and on as needed for temperature control or light
for reading tests. (From Ext. Cir. 8.)
2. To insure uniformity in amounts of blood and antigen for each test,
the loop should be filled so that the blood appears to bulge out and the
drop of antigen is delivered with the dropper in a vertical position.
3. Between each fowl, the blood loop should be rinsed in clean water
and dried on absorbent cotton or a blotter.
36
University of California — Experiment Station
4. The plate on which the test is made should remain stationary.
Rocking or shaking the plate may produce false reactions.
5. The plate should be level so that there is no unevenness in the depth
of different portions of the mixtures of blood and antigen.
The test plate should be thoroughly washed in clean water between
tests and kept free from dust by frequent wiping with a clean towel
while tests are being put on.
6. The most satisfactory temperature for incubation of the tests is
between 80° and 85° F. The reaction takes place more slowly at lower
temperatures. Higher temperatures do not hasten the reaction and have
the disadvantage of increasing the rate of evaporation.
Fig. 12. — Positive (left) and negative (right)
reaction to the rapid whole-blood agglutination
test. (From Ext. Cir. 8.)
7. Iii hot, dry weather, testing should be confined to early-morning
hours.
8. If the testing is done out of doors, it should be in the shade and on
still days only.
9. Do not attempt to read a test after the blood-antigen mixture has
begun to dry because an accurate interpretation cannot then be made.
10. Final negative readings should not be made until after 6 or 8
minutes of incubation. Some reactions develop slowly and will be missed
if the final reading is made too soon. This necessitates provision of glass
covers to place over the tests to protect against evaporation. These covers
also protect against dust.
11. Bright, uniform light is required to facilitate reading of the tests.
For this reason, artificial is preferable to natural light.
12. Fowls that give a doubtful reaction should be retested immediately.
If the reaction is still doubtful, the fowl may be discarded as a reactor
or a blood sample may be taken and sent to a laboratory for a check test
by the tube method.
Although the conduct and reading of tests by the whole-blood method
may appear to be easy to master, the ability to make accurate and
Bul. 674] Diseases of Chickens 37
uniform interpretations of test results is acquired only by extensive
practice.
The procedure to be followed in the interpretation of reactions of
chickens being tested under the National Poultry Improvement Plan
is as follows :
Various degrees of reaction are observed in this as in other agglutination tests.
The greater the agglutinating power of the blood, the more rapid the clumping and
the larger the clumps. A positive reaction consists of a clumping of the antigen in
well-developed violet flocculi surrounded by clear spaces. ... A somewhat weaker re-
action consists of small but still clearly visible clumps of antigen surrounded by
spaces only partially clear. The interpretation of these partial reactions should be
the same as that of similarly incomplete "tube method" [slow serum] agglutination
reactions (i.e., strongly suspicious, weakly suspicious or questionable). Between
this point and a negative reaction, there sometimes occurs a very fine granulation
barely visible to the naked eye; this should be disregarded in making a diagnosis.
The very fine marginal flocculation which may occur just before drying up is also
regarded as negative. ... As a result of more than a year of experience in testing
with this antigen, it has been decided to regard as definitely positive only those
reactions which appear within 1 minute after mixing the antigen and blood, while
those which appear more slowly are regarded as suspicious. 18
The opinions of research workers and livestock disease control officials
differ with respect to the relative efficiency of the rapid whole-blood test
and the slow serum test. Some consider the two to be of equal value.
Others state that their experimental evidence shows that, as a rule, a
flock repeatedly tested by the whole-blood method is likely still to con-
tain infected birds which can be detected by the slow serum test ; and,
therefore, that the whole-blood test is useful for reducing" the amount of
pullorum disease in a flock to a low level but is not a dependable method
for eradication of the disease. As a result, official testing in some states
may be done by any of the three methods, in some by the rapid or the slow
serum method, and in some by the slow serum test only. Official testing
under the National Poultry Improvement Plan may be done by any of
the three methods.
The Skin, or Pullorin, Test. — The pullorin test is made by injecting
into the skin of the wattle a small amount of a fluid containing killed
pullorum-disease organisms or substances extracted from the organisms.
A reaction is indicated by the presence of a swelling of the wattle in
which the pullorum is injected. The results of extensive trials of this
test indicate that it is not a satisfactory means of detecting carriers of
pullorum disease.
Necessity for Repeated Agglutination Tests. — Repeated blood tests
by any of the agglutination methods are necessary for the elimination
18 Excerpt from : United States Bureau of Animal Iudustry. The National Im-
provement Plan. U. S. Dept. Agr. Misc. Pub. 300:23. Eevised January, 1940.
38 University of California — Experiment Station
of all of the fowls in a breeding flock that harbor Salmonella pullorum.
Some of the reasons for the failure of a single test to detect all of the
infected fowls are as follows : (1) certain of the birds may have acquired
the infection too recently for the production of sufficient agglutinins in
their blood to cause an agglutination reaction; (2*) some of the birds
may become infected after the test, either from association with infected
birds or from contaminated litter and soil ; (3) the amount of agglutinins
in the blood of a fowl that is a carrier of S. pullorum is variable and
therefore infected fowls will sometimes fail to react to the test.
Proper Application of the Agglutination Test. — There is ample evi-
dence to show that the intelligent and systematic application of the
agglutination test is an effective and practical means for preventing
pullorum disease in both chicks and breeding flocks.
Success in such an undertaking requires that all fowls in breeding
flocks be tested frequently; that all reactors be promptly removed from
the premises after each test; that houses, yards, and appliances be kept
in a sanitary condition and be given a thorough cleaning and disinfection
after each test ; that tested stock be not allowed to intermingle with un-
tested stock, or, better still, that tested and untested stock be not kept
on the same farm ; and that additions to the flock in the form of hatch-
ing eggs, chicks, or grown stock be from known pullorum-disease-free
sources. Complete eradication of the disease from a flock will usually
require several years when annual testing is the method employed. In
some instances this method may serve only to keep the number of in-
fected fowls so small that serious loss occurs infrequently in either the
breeding fowls or their progeny.
More rapid progress in eradicating the disease from a breeding flock
can be made, however, by retesting at intervals of a month or 6 weeks
until none of the fowls react. This can be expected to require from one
to five retests. Such a testing procedure should be started early enough
so that one or two completely negative tests can be obtained before the
hatching season begins. If the flock has been tested solely by the whole-
blood method, it would be desirable to make one or more additional
tests by the tube method. After pullorum disease has been eradicated
in this way, the flock and its progeny should be tested annually.
Reasons for Failure to Eradicate the Disease from Flocks That Are
Tested. — Cases of apparent failure of the agglutination test to accom-
plish much towards the eradication of infection in flocks can usually be
explained by careful investigation of conditions. Some of the reasons
for such failures are as follows :
1. Failure to test 100 per cent of fowls in a flock.
2. Failure to remove reactors from the flock promptly.
Bul. 674] Diseases of Chickens 39
3. Retaining reactors on the farm for egg-producing purposes.
4. Feeding raw infertile eggs from unknown sources.
5. Failure to properly dispose of offal from reactors killed for home
consumption.
6. Buying stock (eggs, chicks, adults) from flocks not free from pul-
lorum disease.
7. Custom hatching for poultrymen who have not tested their flocks.
8. Returning birds to the flock from poultry shows and egg-laying
contests without first quarantining and testing.
9. Failure to clean and disinfect the houses after the removal of
reactors.
10. Mistakes in numbering blood vials.
Application of the Test to Pullets. — The agglutination test can be
applied to pullets shortly before egg production has started. This prac-
tice is desirable from the standpoint of avoiding possible spread of in-
fection through the consumption by clean birds of floor or soft-shelled
eggs laid by any infected birds that may be in the flock. But unless the
pullets are from a known pullorum-disease-free source, they should be
tested again before their eggs are used for hatching, even though none
reacted to the test.
INFECTIOUS BRONCHITIS
This disease was first recognized in 1931 in North Dakota. By 1933
it had been identified in several midwestern states and in California
and become popularly known as "gasping disease" or "chick bronchitis."
Its distribution is now nationwide. Probably earlier outbreaks in some
sections were mistakenly taken for laryngotracheitis, which it closely
resembles.
Originally the disease was believed to be confined to young chicks.
More recently, however, its occurrence in flocks of adult chickens has
been reported. The reports indicate, however, that infection in adults
is very infrequent. One investigator states: "Of the scores of farms
suffering from the ravages of this disease in baby chicks, only two
reported respiratory disturbances in older fowls." Another advises:
"Usually it occurs in young chicks but occasionally the disease is spread
to the adults on the same farm." Numerous flocks of laying age on Cali-
fornia farms have, during recent years, been affected with a respiratory
disease which so closely resembles infectious bronchitis that it was pre-
sumed to be the same. At present, however, this is regarded as unrelated
to either infectious bronchitis or laryngotracheitis. It is discussed more
fully on pages 41-45.
Cause. — Infectious bronchitis is caused by one of the group of in-
fectious agents known as filterable viruses. It is most abundant in the
40 University of California — Experiment Station
exudate and tissues of the affected respiratory organs, and has also
been demonstrated in livers, spleens, kidneys, and blood. In exudate,
frozen, dried, and stored in a refrigerator, the virus has remained alive
for 180 days. There is little definite information concerning the time
the virus will remain active under natural conditions. Failure to trans-
mit the disease by injection of exudate from dead birds suggests that
the virus perishes quickly after the death of the host. On the other
hand, the conditions under which some natural outbreaks have occurred
suggest that the virus may remain active in a contaminated brooder
house or equipment for several months. Field evidence indicates that
recovered birds may become healthy carriers of the virus, but this has
not been demonstrated experimentally.
Symptoms. — Gasping is the most characteristic and predominant
symptom. When badly affected, the beak of the chick is pointed upward
and opened wide at each inspiration. Convulsive coughing is also seen.
Many chicks emit a peculiar sharp chirp. Chicks less severely affected
exhibit such symptoms irregularly, but if one is held close to the ear,
short, crackling sounds may be heard. Nasal discharge and swollen
sinuses may be the predominant symptom, especially in chicks a few
weeks old. Depression and weakness are seen in the advanced stage.
The disease occurs most frequently in chicks under 3 or 4 weeks old.
It has been reported in birds as young as 2 days. The disease spreads
rapidly and is apt to infect nearly all of a flock within a brief period.
The mortality is nominal in most outbreaks, the principal loss coming
from growth retardation. In some outbreaks, however, the mortality
may amount to from 25 to 90 per cent of those affected, and is likely to
be greatest in flocks of very young chicks.
Accumulations of clear, turbid, or thick yellow mucous exudate, or
caseous plugs, in the lower trachea and bronchi are the most character-
istic autopsy finding. The same sort of exudate occurs in the nasal cham-
bers when they are involved. Caseous or thick viscid mucus is occasionally
seen in the larynx and air sacs.
Transmission. — The disease spreads readily from affected to healthy
fowls by contact with either infected chickens or contaminated material.
It is usually easily transmitted by the intranasal or intratracheal injec-
tion of exudate into the trachea or nasal passages. The source of the first
infection on a farm is often obscure. Some outbreaks, however, have been
traceable to hatcheries, particularly those which raise "started chicks"
in batteries in the building with the incubators.
Diagnosis. — In young chicks, the symptoms and autopsy findings
alone are usually sufficient for recognition of infectious bronchitis ; but
if there are nervous symptoms, the disease must be differentiated from
Bul. 674] Diseases of Chickens 41
avian pneimioencephalitis. In older birds it must be differentiated from
laryngotracheitis and avian pneumoencephalitis, and, when there is
nasal involvement, from infectious coryza. This often requires labora-
tory procedures which cannot be done on a farm.
Prevention. — The only recommendations for prevention that can be
given at present are the strict application of the measures of hygiene
and sanitation ; making as certain as possible that all new stock comes
from a clean source, and that houses and equipment are thoroughly
cleaned and disinfected after an outbreak. Contact between survivors
of an outbreak and susceptible birds should be avoided. Recovered birds
are immune, but no safe method of artificial immunization, has been
found. Cloacal vaccination, as used for laryngotracheitis, is not appli-
cable because, first, it could not be applied early enough to protect very
young chicks, and, second, infection of the respiratory organs can be
produced by applying virus to the cloaca.
In order to eradicate the disease from establishments where continuous
brooding is practiced, such as broiler plants, it is necessary that opera-
tions be suspended long enough to get rid of all chickens and to thor-
oughly clean and disinfect all pens, rooms, and equipment. Hatcheries
which deal in started chicks should have separate quarters, equipment,
and personnel for each operation.
No effective treatment has been found.
AVIAN PNEUMOENCEPHALITIS 17
During 1940 a type of nervous disorder which had not been seen pre-
viously, or at least not in sufficient amount to attract attention, occurred
in many flocks of growing chicks. Nearly all outbreaks of this disease
either closely followed, or were accompanied by, a respiratory disease
which markedly resembled and was believed to be infectious bronchitis
(see preceding section). It has since been found, however, that the re-
spiratory trouble is probably not in any respect related to infectious
bronchitis. Instead, it appears to be a part of a disease of growing chicks
in which both the respiratory organs and the central nervous system
may be involved.
In experimental studies conducted during the present year (1942),
it has been found that the disease is not confined to growing chickens but
may also affect nearly mature pullets and laying chickens of any age.
17 Less than a year has elapsed since the cause of this disease was determined and
progress in the experimental studies of it thereby made possible. Consequently,
knowledge concerning certain fundamental phases of it are still fragmentary and
future findings may necessitate revision of some of the statements and ideas ex-
pressed here. The disease first became known as "a respiratory nervous disorder." It
is now proposed, however, that this be replaced by the appropriate, descriptive, scien-
tific name of "avian pneumoencephalitis."
42 University of California — Experiment Station
Furthermore, it has been identified in two flocks of young turkeys and
has been produced in young turkeys by inoculation with material from
infected chickens.
Cause. — This disease, like infectious bronchitis, is caused by a fil-
terable virus. It has so recently been identified that knowledge of its
characteristics is far from complete. The virus, however, has been shown
to be widely distributed in the body during the early stages of the disease,
especially in severely affected chickens. It has been demonstrated in the
brain, spleen, blood, lungs and air sacs, and exudate in the trachea of
infected chickens. The virus has also been found in intestinal contents
and in droppings collected soon after being voided. In lung tissue that
has been frozen and dried or placed in 50 per cent glycerin and stored
in a refrigerator, the virus has remained alive for 3 to 6 months. It grows
readily in developing chick embryos, a characteristic which is a great
aid in experimental studies of the disease. The conditions which are
favorable to, and the time of survival of virus under natural conditions
outside the body of a living chicken have not as yet been learned, but the
results of very limited investigation of this point suggest that it would
remain infective only a short time in a contaminated poultry house.
There is, however, some experimental evidence that recovered chickens
may carry the virus and therefore be dangerous to other chickens for
a considerable period.
Symptoms in Chicks. — Most outbreaks of the disease in chicks have
begun as a respiratory trouble, symptomatically indistinguishable from
infectious bronchitis (see p. 39) but, within a few days, from a few to
several of the chicks have developed symptoms of involvement of the
nervous system. The respiratory phase has usually passed off within a
week or two. The nervous symptoms, however, have been seen for a con-
siderably longer time.
The respiratory symptoms are gasping, coughing and rales or rattling
breathing sounds, and many of the affected chicks emit a peculiar, rapid
low chirp.
The symptoms from involvement of the nervous system are quite
varied in different individuals. They consist of unsteady or staggering-
gait, partial or complete paralysis of one or both legs, tremor or shaking
of the head or whole body, and loss of coordination of action of the neck
muscles, as a result of which, the head may be drawn straight back be-
tween the shoulders, downward and backward toward the breast, twisted
to one side or the other, or drawn to the right or left. The chickens may
walk in circles or backwards. The appetite may be unimpaired and in
spite of inability to control muscular movement many chickens will
manage to consume enough food to keep themselves fairly well nour-
Bul. 674] Diseases of Chickens 43
ished. On the other hand, affected chickens may become droopy, eat
little or no food, and quickly become emaciated and weak. In cases of
fatal infection, the chickens are likely to become prostrated, show
clonic spasms or a rhythmic twitching of the body, and go into a state
of coma before death. In numerous experimentally produced cases, death
has occurred in less than 24 hours after the first symptom was observed.
Although some chickens have recovered from the nervous affliction,
nearly all which escape death retain the symptoms indefinitely.
The most common findings on post-mortem examination of chicks have
been cloudiness or thickening of the air sacs and, in many cases, also of
the thin membranes of the abdominal cavity with a film of yellowish
exudate and varying amounts of yellowish or clear mucus in the trachea
and large bronchi. However, in many cases, particularly those with nerv-
ous symptoms alone, no visible lesions have been present. Many of the
acute cases produced by inoculation have shown numerous small hemor-
rhages beneath the mucous membrane or lining of various portions of
the digestive tract, the proventriculus in particular; but such lesions
have seldom been seen in infected chicks or farms.
As was stated before, both respiratory and nervous symptoms have
been present in nearly all outbreaks among chicks. The respiratory phase
has often affected nearly 100 per cent of a flock, the nervous phase from
1 to 45 per cent. In a few instances, however, respiratory symptoms
have been either absent or so very mild that they escaped detection. The
nervous involvement tends to be more rapidly fatal in the younger
chicks. The average mortality is probably between 5 and 10 per cent.
A greater loss, however, may result from unthriftiness of the survivors.
Most of the flocks affected have been from 3 to 10 weeks old, although
outbreaks among younger and older chicks have been reported. The
disease has made but a single visitation on some farms, on others it has
recurred in successive broods of chicks.
Symptoms in Older Chickens. — The pneumoencephalitis virus has
been isolated from a few birds affected with the disease of pullets and
laying hens that is known in different localities by such names as 9-day
pneumonia, California flu, and bronchitis. It is not yet known, however,
that this virus is the sole cause of this type of respiratory disease. Al-
though the symptoms resemble both infectious bronchitis and infectious
laryngotracheitis, this disease appears to be unrelated to either. It has
occurred in many flocks that had been immunized to laryngotracheitis
and a number of attempts to transmit it by the procedures successfully
employed for the transmission of infectious bronchitis and laryngo-
tracheitis have failed. This disease is characterized by a sudden onset and
extremely rapid spread through a flock. The loss from death has usually
44 University of California — Experiment Station
been nominal. The egg production of laying flocks, however, may prac-
tically cease within a week and not return to a profitable level until 1 or
2 months later. Affected chickens cough, gasp, and manifest other symp-
toms of difficult respiration. They may also become listless and lose in-
terest in food. Improvement is likely to be seen within a week or 10 days.
At autopsy varying amounts of clear or cloudy liquid or viscid mucus
are found in the trachea. Exudate in the trachea of the thick, yellowish
and bloody nature which characterizes laryngotracheitis has rarely been
seen.
Another type of disease of laying chickens, with which the pneumo-
encephalitis virus has recently (August, 1942) been identified, was mani-
fested as follows : The first effect of the disease was to cause a decrease in
appetite, especially for mash. Within 2 or 3 days, depression or dullness
of from a few to several of the chickens was seen. During the follow-
ing few days more chickens showed these symptoms and, in some out-
breaks, by the end of a week practically all the chickens in a pen would
be sitting about on the roosts or floor and eating little or no food. Egg
production has uniformly decreased rapidly, sometimes ceasing entirely.
At the beginning of some of the more severe outbreaks, a large number of
floor and yard eggs, many with soft shells, were laid. Some coughing has
usually been heard, but respiratory symptoms were not prominent. In
addition to the above, a variable number of the chickens developed nerv-
ous symptoms like those described for chicks (p. 42). Affected flocks
have begun to improve within a week or 10 days after depression was
first seen and have quickly regained normal appearance. Egg production,
however, has increased more slowly. The mortality has varied from a
negligible number to as high as 22 per cent of the flock. On some farms
on which the disease has appeared for the first time, it has progressed
from pen to pen until the whole population, regardless of age, has become
infected. Lesions by which the disease could be identified have not been
found on post-mortem examination of dead chickens.
Transmission. — Experimentally, the disease has been transmitted by
injecting fresh blood or tissue or exudate of the respiratory organs,
brain, or spleen of infected chickens into the nasal passages, trachea, air
sacs, breast muscle, brain, abdominal cavity, crop, or bursa of Fabricius
or under the skin of normal chickens which ranged in age from a few
days to more than two years. Transmission by pen or cage contact has
also been readily accomplished. The means by which the infection may
be first introduced into a farm, however, are still too indefinite to be
discussed here. Outbreaks in chicks in some instances have been pre-
ceded by the occurrence of the respiratory disease in older chickens on
the farm. In some cases the situation has been reversed.
Bul. 674] Diseases of Chickens 45
Diagnosis. — A combination of respiratory and nervous symptoms in
a group of growing chicks is at present considered sufficient for fairly
certain recognition of the disease. Laboratory procedures must be em-
ployed to differentiate it from infectious bronchitis, however, if only a
very small percentage of a flock shows nervous symptoms. The disease
does not produce any constant and characteristic lesions which enable
one to recognize the disease by post-morten examination. Yellowish- gray
cloudiness of the ordinarily clear membranes which form the air sacs
is the most frequent lesion encountered, but this, in many cases, is absent
or indefinite.
The respiratory disease of older chickens must be differentiated from
infectious bronchitis and infectious laryngotracheitis, and this usually
will require laboratory procedures. It is likely not to be laryngotrache-
itis, however, if none or but a few of the affected chickens die, if the flock
has recently been vaccinated for laryngotracheitis, or if no bloody mucus
is coughed up or is found in the trachea by post-mortem examination.
These, however, are not certain differential factors. Symptoms in laying
flocks, as described on page 44, are highly suggestive but are not diag-
nostic of infection with the pneumo-encephalitis virus, and, therefore,
laboratory procedures are required for positive identification of even
such cases.
Control mid Prevention. — A measure that appears worth while for
flocks of chicks or older chickens affected with pneumoencephalitis con-
sists in endeavoring to stimulate the birds' food consumption by some
modification of the feeding method, such as giving the mash in meals
instead of keeping it before the birds all of the time, supplying extra
milk products, and giving an extra daily feeding of fresh tender greens,
moistened mash, and rolled barley soaked in milk. This may reduce the
number of unthrifty birds in flocks of chicks and shorten the period of
low egg production in laying flocks.
By careful observance of precautions against carrying the infection
from one pen to another, it may be possible to confine the disease to one
or two pens. The attendant should always take care of the affected pens
last, should have coveralls which are worn only in the infected pens,
should thoroughly wash his hands, using plenty of soap, when he has
finished caring for an infected pen, and should have separate utensils
for use in the infected pens. The chickens should be kept inside, and
cases showing nervous symptoms should be destroyed as quickly as they
appear.
Houses and equipment should be thoroughly cleaned and disinfected
after an outbreak and the survivors probably should be segregated from
other chickens which are on the farm at the time or added later. To
46 University of California — Experiment Station
eradicate the disease from pullet-raising or broiler plants on which
brooding is continuous, it is likely to be necessary to suspend operations
until all chickens can be disposed of and the pens, rooms, and equipment
thoroughly cleaned and disinfected.
INFECTIOUS AVIAN ENCEPHALOMYELITIS (EPIDEMIC TREMOR)
This disease of the nervous sytem of chickens has been present in
northeastern states since 1930. It was identified in California for the first
time in December, 1941, in chicks of the New Hampshire breed. Since
then the disease has occurred in a few additional flocks of New Hamp-
shires and White Leghorns as well. It was at first termed "epidemic
tremor" because a prominent and striking symptom is tremor or rapid
shaking of the head. This name is not strictly applicable, however, be-
cause subsequent studies have revealed that less than half of affected
chickens show the tremor symptom.
Cause. — The disease is caused by a filterable virus. The brain of af-
fected chicks is the most reliable source of virus, but it has been demon-
strated also in the spleen and liver.
Symptoms. — The first symptom to appear is ataxia, or unsteadiness
and inability to control movements of the legs, which becomes progres-
sively more pronounced. Many chicks lose the ability to stand, and sit
and walk on their hocks. Some become unable to move at all and soon
die. In a variable number of the chicks, the ataxia may be followed in
from a few to several days by the appearance of a rapid tremor of the
head. This becomes more prominent when the chicks are disturbed.
Death may take place soon after the onset of symptoms, or after a more
protracted illness. A considerable number of the affected usually survive,
however, and the majority of these retain the nervous symptoms. In
fact, the number of affected chicks which die from being trampled by
the healthy ones may be greater than that from the direct effects of the
disease. A flock usually becomes affected at the age of 1 to 6 weeks. New
cases can continue to develop for several weeks. The total number of
chicks to contract the disease ranges from 5 to 50 per cent or more of the
flock. On some farms, successive hatches of chicks have become infected,
on others the disease has appeared very irregularly or only once.
Transmission. — Some who have studied the disease report having ob-
tained both field and experimental evidence that the infection is trans-
mitted through the egg from the hen to its progeny and that this is a
probable means of introducing the disease to a flock hitherto free from
it. This view, however, is not supported by the experimental findings of
all investigators.
Spread of the disease by direct contact has been observed both in farm
Bul. 674] Diseases of Chickens 47
flocks and in experimental groups of chicks. Experimentally the infec-
tion has also been transmitted by injecting brain tissue of diseased chicks
into the brain or nasal passages of healthy ones.
Diagnosis. — It is not possible to recognize avian encephalomyelitis in
chicks from symptoms alone. Neither can this be done by post-mortem
examination of dead chicks on the farm because the disease produces no
lesions which are visible to the unaided eye. Therefore a diagnosis can
be made only at a laboratory by microscopic examination of the brain
and inoculation of healthy chicks.
Chicks fed a diet deficient in vitamin E develop symptoms much like
those of avian encephalomyelitis and therefore this possibility must be
considered in any outbreak. Although poultry rations are not usually
lacking in vitamin E, it appears that the vitamin may be destroyed or
inactivated when fish oil is used at high levels or has become rancid. The
symptoms of avian encephalomyelitis also are similar to and must be
differentiated from the nervous phase of pneumoencephalitis in chicks,
described in the preceding section.
Control and Prevention. — Affected chicks should be immediately
taken out of the flock and either destroyed or kept separate and sold for
meat as soon as they reach broiler size. This may both check the spread
of the disease and remove from the farm possible reservoirs of infection
of other chickens.
Since the possibility of transmission through the egg exists, it would
be inadvisable to purchase hatching eggs or chickens of any age from a
flock in which the disease is or has been present. For the same reason,
survivors of an outbreak might be considered unsuitable for breeders.
INFECTIOUS LARYNGOTRACHEITIS
This disease was previously designated as "infectious bronchitis," but,
since studies of the pathology of the disease have shown that it affects
principally the larynx and trachea, the more correct term, infections
laryngotracheitis, has been adopted. The disease has become widespread
and of major economic importance in the United States and Canada,
but is not known to have occurred elsewhere in the world, except in
Australia, where it was identified in 1935. Reports of its occurrence in
England, Germany, and Spain are of doubtful authenticity.
Cause. — The disease is caused by a type of infectious agent known as
a "filterable virus," which is found principally in the exudate that
forms in the larynx and trachea. Exudate from an infected fowl, when
dried and kept under suitable conditions, has remained capable of pro-
ducing the disease for more than a year.
It has been shown experimentally that the virus is quickly destroyed
48 University of California — Experiment Station
by exposure to moderate temperature (55° to 75° C), does not survive
longer than 90 days at room temperature, may be killed by exposure to
direct sunlight in 7 hours, survives in the body of a dead chicken only
until decomposition of the tissues begins, and is readily destroyed by a
3 per cent solution of cresol disinfectant and a 1 per cent solution of
sodium hydroxide (lye). The importance of these findings is that they
indicate that the virus is not likely to survive in contaminated poultry
houses or equipment from one season to another and that either a cresol
disinfectant or a lye solution is an efficient disinfectant for use on poultry
farms in which the disease has occurred.
Fig. 13. — An advanced case of infectious laryngotracheitis, showing attitude
during expiration. (From Ext. Cir. 8.)
It has been found that chickens may carry the virus in their tracheas
for as long as 16 months after recovery from the disease. Such "healthy
carriers" can infect susceptible chickens with which they become asso-
ciated and are the probable source of the infection causing annual out-
breaks among the young stock on many farms.
Symptoms. — The predominant symptoms of the disease are coughiing
and gasping for breath. The affected fowl assumes a sitting position,
with the neck drawn in, the beak pointed downward, and the eyes closed
(fig. 13). At each inhalation, the head is thrown forward and upward,
with the beak opened (fig. 14) and the intake of air is accompanied by
a loud wheezing sound. Spasmodic exhalation or coughing is frequent
and often results in the expulsion from the trachea of a mass of clotted
blood. Examination may reveal the larynx to be nearly filled with bloody
or yellowish, thick mucus or with caseous material, while in other cases,
in the live bird, the cause of respiratory difficulty is not visible. Rarely,
the disease may also involve the eyes and nasal passages.
Bul. 674] Diseases of Chickens 49
The onset of the disease is sudden and as a rule the spread through
a flock is very rapid. An outbreak usually causes a mortality of from 5
to 25 per cent or more of a flock during a period of from 2 to 4 weeks. The
disease then disappears about as suddenly as it began. Laying flocks
usually almost cease production and do not again attain a normal pro-
duction rate for 1 or 2 months. Occasionally the spread is slow and evi-
dence of the disease may exist in a flock for weeks.
■—„-. — . ....I. it...... . .
Fig. 14. — Same fowl as in figure 13, showing attitude during inspiration.
(From Ext. Cir. 8.)
When there is more than one flock on a farm, it may attack one flock
after another. Recurrences of the disease in the same flock do not take
place, however, unless only a small number of the fowls were initially
infected, the reason being that recovered fowls are permanently immune.
The majority of the fowls that die do so within 1 or 2 days after
symptoms appear. A large percentage of affected fowls that survive the
first 2 days of sickness recover. Not infrequently the value of the eggs
lost by the decrease in production exceeds that of the fowls which die.
On autopsy, all organs are apparently normal with the exception of
the larynx and trachea. These organs are usually wholly or partially
filled with mucus and clotted blood and their linings inflamed. In some
cases of 3 or 4 days' duration, the mucus in the larynx becomes caseated.
Occasionally caseous mucus is found extending the entire length of the
50 University of California — Experiment Station
trachea. In some birds, the amount of clotted blood present exceeds that
of mucus. The collection of mucus is sometimes confined to the lower
portion of the trachea, the upper portion of the trachea and the larynx
being entirely free. The lungs appear normal except for small areas of
congestion. Death in most cases appears to be due entirely to asphyxia-
tion, which occurs when the larynx or trachea becomes filled with mucus
or clotted blood.
Birds Affected by the Disease. — Laryngotracheitis has occurred or
been produced only in chickens and pheasants. Domesticated ducks,
turkeys, pigeons, and wild and free-flying species of birds, including
sparrows, crows, starlings, doves, and quail, have been found refractory
and so, too, have rabbits, guinea pigs, and white rats.
Diagnosis. — Many outbreaks of laryngotracheitis can be readily rec-
ognized by the characteristic symptoms and autopsy findings, and the
rapidity of spread of the disease through a flock. Almost identical char-
acteristics, however, are presented by infectious bronchitis of chicks and
the similar disease in adult chickens (p. 43). A respiratory disease of
this character in young chicks, however, is not likely to be laryngotrache-
itis, for this disease has rarely been seen in such young birds. A respira-
tory disease of older chicks, which has symptoms of laryngotracheitis
but which is accompanied by few or no deaths and the collection of clear
or slightly cloudy mucus, instead of yellowish or bloody, in the trachea is
likely to be infectious bronchitis. In many cases, however, a positive
diagnosis cannot be made on a farm, but must be based upon the results
of transmission, cross-production, and other tests at a laboratory.
In some outbreaks of a severe type of coryza, many of the affected
fowls have tracheal involvement, and coughing and gasping are promi-
nent symptoms. The diagnostic question in such cases is to determine
whether the fowls have coryza alone or are affected with both coryza and
laryngotracheitis. Laboratory procedures are usually necessary to pro-
vide the answer.
Vaccination. — Vaccination procedure is based upon the discovery
that the mucous membrane of the cloaca and bursa of Fabricius (fig.
15) is susceptible to the virus of laryngotracheitis, that infection of these
parts does not cause a systemic disturbance or spread to the respiratory
tracts, that the cloacal infection subsides in about 7 days, and that the
fowl is thereafter immune to infection of the respiratory tract.
The vaccine consists of exudate taken from the trachea of artificially in-
fected chickens or, as in fowl pox (fig. 23, p. 22) , the chorioallantoic mem-
brane of chicken embryos on which the virus has been propagated. The
two types of vaccine are labeled by producers respectively as "chicken
origin" and "egg propagated" or "chick-embryo origin." The virus-
Bul. 674]
Diseases of Chickens
51
bearing exudate or embryo tissue, after removal, is dried and finely
powdered. This treatment, when properly done, does not reduce the
virulence of the virus. This vaccine, therefore, will cause severe infection
Fig. 15. — (1) Bursa of Fabricius; (2) large intestine;
(3) cloaca; (4) vent, or cloacal lips. (From Ext. Cir. 8.)
if it is introduced into the respiratory passage of a susceptible chicken.
It must he handled carefully and strictly in accordance with instructions.
For use in vaccination, the powdered virus is suspended in a solution of
glycerin.
Fig. 16. — Take from laryngotracheitis vaccination: left, swelling of the
cloacal lips; right, reddening of the cloacal mucous membrane. (From
Ext. Cir. 8.)
The vaccination procedure consists in brushing the vaccine onto the
cloacal mucous membrane ; the cloacal lips are forced open to expose the
membrane which is then brushed until redness or even bleeding is pro-
duced. Another, although little-used, method of vaccinating chickens
under the age of 5 to 5% months consists of injection of the vaccine
directly into the bursa of Fabricius through a blunt, slightly curved
hypodermic needle. The resultant take, or infection of the mucous mem-
brane (fig. 16) , consists of swelling of the cloacal lips, redness and swell-
52 University of California — Experiment Station
ing of the mucous membrane, and the presence on its surface of mucus,
often yellow and flecked with blood. A take usually reaches maximum
intensity on the fifth day and by the seventh day has nearly disappeared.
In contrast to survivors of respiratory infection, the virus does not
persist in the cloaca or bursa of Fabricius after the reaction subsides.
The birds should be examined on the fifth day after vaccination, and
any that do not show a definite take should be revaccinated immediately.
If not revaccinated, the birds without a take can be expected to acquire
severe respiratory infection from the virus eliminated by the birds with
takes. Failure to obtain vaccination takes may be due either to faulty
administration or to impotence of the vaccine. The potency of vaccine
is likely to be adequate when it leaves the producing laboratory but can
be easily reduced by exposure to warmth during transit to and after
reaching the farm. It should be protected against warmth even while it
is actually being used for vaccination.
No special additional after care is required.
Chickens can be vaccinated at any time after they reach the age of 6
weeks, but preferably before they begin to lay. All instructions furnished
with the vaccine should be faithfully obeyed.
Vaccination is indicated:
1. For the prevention of the spread of the disease on a farm after it
has appeared in one pen. In such cases the noninfected pens should be
treated first.
2. For young stock on farms where the disease has occurred in the
past and where survivors of a previous outbreak remain.
3. For susceptible fowls which are added to a flock in which the disease
is or has been present ; or for a susceptible flock to which known survivors
of the disease are to be added.
4. For healthy flocks, either already existing or newly established in
a congested poultry district in which the disease is prevalent.
Vaccination is not indicated:
1. As a preventive measure in a flock not previously infected unless it
is located in a congested poultry district in which the disease is prevalent.
2. For the control of an outbreak of any respiratory disease not defi-
nitely diagnosed as laryngotracheitis.
3. For a portion of the susceptible birds on a farm, unless the birds
not vaccinated are too young, are well segregated, and are to be vacci-
nated as soon as they reach suitable age.
4. For use by persons unfamiliar with the hazards attendant upon the
use of a virulent live- virus vaccine.
Prevention. — The strict application of the principles of hygiene and
sanitation (p. 22) should be adequate to prevent the introduction of the
Bul. 674] Diseases of Chickens 53
disease into a flock not located in a poultry district. Particular attention
should be given to the source of added stock and any article that is used
in poultry houses.
Prevention of recurrence of the disease on a farm after an outbreak
without annual vaccination has been accomplished by the following-
procedure :
1. Removing* from the premises all birds which have had or have been
exposed to infectious laryngotracheitis.
2. Thoroughly cleaning and disinfecting the outer clothing of the
attendant and all buildings and equipment used for housing and care
of the condemned chickens.
3. Leaving the houses and equipment unused for at least 3 months
after they have been cleaned and disinfected.
4. Retaining chicks for restocking on the premises provided they are
well separated from the condemned birds and are definitely known to
have escaped infection.
5. Securing new stock (preferably as baby chicks) from absolutely
clean flocks.
These measures would be of questionable effectiveness in poultry dis-
tricts in which infectious laryngotracheitis is prevalent.
Treatment. — No medicinal treatment for individual birds or a flock
has been found to have sufficient merit to warrant its use; in fact, drop-
ping chemicals into the trachea or spraying them over fowls on the
roost may increase the respiratory distress of affected birds. The reason
that many of the chemicals that have been tried as a treatment for the
disease have appeared to be beneficial is that a large percentage of in-
fected birds recover spontaneously without treatment.
When difficult breathing is due to stoppage of the larynx and upper
trachea, quick relief and recovery can usually be obtained by careful
removal of the material with forceps. This is the only type of treatment
that has been found worth while.
INFECTIOUS CORYZA, OR COLDS
Coryza (the scientific name for nasal catarrh or cold in the head) is
probably the most commonly occurring and widespread of all diseases
of poultry. In the past, environmental conditions, such as damp weather,
sudden changes in temperature, crowding, and drafty or poorly venti-
lated houses, were regarded as necessary predisposing or even primary
causative factors, and the microorganisms present in the nasal chambers
of affected chickens were presumed to be only secondary factors. In 1933
and 1934, however, several investigators, widely scattered and working
independently, succeeded in isolating from the nasal exudate a species
54 University of California — Experiment Station
of bacteria which, when injected into the nasal passages of healthy
chickens, would reproduce the symptoms of the natural disease. This
type of respiratory infection, to which the name "infectious coryza" has
been given, is very prevalent on poultry farms.
Cause. — The bacterium named Hemophilus gallinarum, the fowl-
coryza bacillus, is considered to be the primary cause of infectious coryza.
This organism is similar in form and growth requirements to the bacillus
associated with influenza of man and certain domesticated animals. It
grows sparsely in cultures; this may be why it was not identified earlier.
Fig. 17. — Chickens with infectious coryza.
The bacillus can be readily demonstrated microscopically in exudate and
obtained in culture during the early stages of the disease. In older cases,
however, it is difficult or impossible to identify the organism because
of the numerous other bacteria which are present. Consequently, to
identify a field case as infectious coryza, it is often necessary to in-
oculate chickens with the nasal exudate in order to secure for examina-
tion a case which has just begun to show symptoms.
The coryza induced by inoculation with a culture is usually of shorter
duration than that from natural infection or that induced by inocula-
tion with exudate from a field case. This has raised the question of
whether the natural disease is caused by Hemophilus gallinarum alone
or in combination with another causative agent. On this point the opin-
ions of research workers differ. Some believe that the relative mildness of
disease produced by inoculating chickens with cultures may be due to
reduction in the virulence of the organism by cultivation in an artificial
medium. Two other organisms, one termed "coccobacilliform bodies"
Bul. 674]
Diseases of Chickens
55
and the other Shigella nasalis, have been isolated and are said to be
capable of acting in conjunction with the f owl-coryza bacillus to increase
the severity of the infection produced by the latter alone. From the
preceding it is seen that the cause of infectious coryza is not as yet fully
understood.
Fig. 18. — Edema of the wattles produced by injection of a culture
of the f owl-coryza bacillus.
In addition to the above, the fowl-cholera bacillus may, under certain
circumstances, become localized in the nasal passages of chickens and
produce a coryza of the same type as that under discussion. This disease
is dealt with in the same way.
Symptoms. — Infectious coryza has shown a remarkable variability
in its severity and harmfulness to a flock. The mildest type of the disease
occurs as a simple coryza, the only symptom of which is a nasal discharge,
either persistent or of short duration. Indications of systemic effect, such
as droopiness and diminished appetite, are absent.
In the severer types of the disease the coryza is complicated by other
manifestations. One frequently seen is edema or puffiness (fig. 17) of
the face which may extend, especially in males, to the wattles (figs. 18,
56 University of California — Experiment Station
19). The latter condition, however, often results from other causes (see
p. 75) and is not indicative of infection with the fowl-coryza bacillus
unless accompanied by other symptoms of coryza. Other complications
are swelling beneath the eyes and involvement of the trachea, bronchial
tubes, and even the air sacs.
Fig. 19. — Edema of wattle from natural infection with
coryza. The chicken also has swelling under the eyes,
which is not clearly shown in the photograph.
The heaviest losses occur when a large number of the affected chickens
have involvement of the trachea and bronchi. In such cases, coughing
and gasping are prominent symptoms and there are numerous deaths
from suffocation, which gives the disease a close resemblance to laryngo-
tracheitis. In addition the fowls are depressed, have diminished appetite,
and become progressively emaciated.
The course of infectious coryza in a flock is usually prolonged, ex-
tending over a period of several weeks or months. The resultant mor-
tality varies from a negligible number to more than 50 per cent of a
flock. In an extreme case the disease persisted in a flock of 2,500 pullets
from May to December and ultimately caused the destruction of all the
birds. In many outbreaks, however, the loss from decreased egg produc-
Bul. 674] Diseases of Chickens 57
tion and the development of worthless culls exceeds that due to im-
mediate mortality.
The mild type of coryza is extremely insidious. The damage which it
does may seem to be so slight that the flock owner disregards its presence
even though a relatively large number of birds may be affected. The
adverse effect on egg production, however, is likely to be considerable,
despite the fact that the birds look well, eat well, and few are dying.
But the greater danger lies in the possibility of a change from a mild to
severe type of disease at any time, with consequent heavy loss. Such a
change can readily be brought about by rapid passage of the disease
from one chicken to another at a laboratory and has been observed on
farms.
Chickens which recover may carry the infection for an indefinite time
and may again develop symptoms. Consequently, after a flock has been
infected once, it is likely to always contain some healthy carriers or
mildly affected birds from which the disease is transmitted to others.
This is believed to be the means by which the infection is perpetuated
on a farm so that it occurs in pullets year after year. Transmission takes
place readily through direct contact between infected and healthy birds.
It can also be transmitted by indirect contact, such as by contaminated
material or clothing of the attendants, but the exact agency through
which this takes place is often obscure.
Species Susceptible. — Pigeons have been found refractory to infec-
tious coryza. The disease has been transmitted to turkeys and the result-
ant disease was of the same character as natural cases of coryza and
sinusitis (swell head) in this species of bird. Hemophilus gallinarum,
however, has not been identified in natural cases of sinusitis in turkeys.
Diagnosis. — Experience has shown that any respiratory disease on a
California farm which has a nasal discharge as a constant symptom,
affects several chickens at a time, and persists in a flock over a period
of weeks or months, and especially one which affects pullets year after
year, is likely to be infectious coryza. It is always well, however, to have
a field diagnosis checked at a laboratory to determine whether the disease
can be transmitted by inoculation of healthy chickens with nasal exu-
date and whether the fowl-coryza bacillus is present. This is particu-
larly desirable for identification of the mild type of the disease. When
the symptoms consist of coryza and edematous swelling of the face or
wattles, laboratory procedures are necessary to determine whether the
infection is with the fowl coryza or the fowl-cholera bacillus. When
symptoms of tracheal involvement — that is, coughing and gasping — in
addition to nasal involvement are present, laboratory procedures are re-
quired to determine whether the disease is coryza alone or a combination
58 University of California — Experiment Station
of coryza and infectious laryngotracheitis if in half -grown or laying
birds, or coryza alone or in combination with infectious bronchitis if in
chicks. It should be apparent from the preceding that definite differen-
tiation of respiratory diseases of chickens in many cases is a difficult
problem.
Prevention. — Measures of hygiene and sanitation (p. 22) conscien-
tiously applied should ordinarily be adequate to prevent the introduc-
tion of infectious coryza on a poultry farm. If a farm is in a congested
poultry district in which the disease is prevalent, prevention by sanitary
measures is more difficult but is more likely to succeed if the chickens
are confined in the houses. Under any circumstances, it is particularly
important that additions to the flock be made only by hatching eggs or
day-old chicks.
The prevention of recurrences of the disease after it has once appeared
on a farm requires complete and permanent separation of survivors of
infected flocks from all other chickens. This may be accomplished either
by segregating the survivors in a separate house on the farm or by de-
populating, which entails removing all survivors of an infected flock
from the premises.
In segregation, the infected fowls should be confined in a house as
far removed from others as possible and be kept thus separated as long
as any of them remain. Extreme care should be taken to see that none
of them escape into pens occupied by others. It is preferable that their
caretaker does not also care for other fowls ; but, if this cannot be done,
the work should be planned so that they are always the last to receive
attention. A separate set of utensils should be provided. This procedure
has been only partially successful on most of the farms on which it has
been tried, and on some it has failed utterly.
For elimination of infectious coryza by depopulating, three plans
have been successfully used :
1. Selling all of the condemned flock as market poultry, and restocking
the farm with chicks.
2. Moving the condemned flock to other premises, usually rented for
the purpose, and restocking with chicks. The fowls removed are main-
tained in their new location until all are disposed of in the usual manner.
3. Rearing the chicks for replacement until the birds are about ready
to lay on other premises where they will not be exposed to coryza. The
condemned flock is then marketed and replaced by the healthy pullets.
In plans 1 and 2 the chicks for replacement may be on hand as long
as 2 months before the older chickens are removed if the brooder houses
are well separated from other poultry houses and separate attendants
and utensils are provided for the chicks. When plan 2 or 3 is adopted,
Bul. 674] Diseases of Chickens 59
it is highly desirable to have separate attendants and equipment for
each of the two flocks.
The vacated houses and the equipment can be used again as soon as
they have been thoroughly cleaned and disinfected. With any one of
the three procedures, the new flock can be expected to remain free from
infectious coryza until it is reintroduced from the outside through non-
observance of sanitary precautions (see p. 22), such as adding pullets,
breeding cockerels, or adult chickens to the flock. To obtain sustained
success from depopulation of a poultry farm in close proximity to others,
exceptional precautions must be taken. Under such circumstances, the
clean flock should be confined to houses and wire netting, preferably
1-inch mesh, enclosed sun porches ; and the areas of the farm on which
poultry houses are located should be well fenced to keep out any stray
chickens from neighboring farms. Depopulation may appear imprac-
tical because of the cost, but it will be found less expensive than the loss
by death, retarded development, and reduced egg production that re-
sults when each year's crop of pullets becomes affected with coryza.
Vaccination with avian mixed bacterin has not proved effective for
the prevention of infectious coryza.
Control and Treatment. — In outbreaks of infectious coryza, some
benefit may be derived from the isolation of affected fowls until they
have recovered. If begun early and conscientiously continued, the spread
of the infection may be so retarded and the severity so reduced that the
mortality will be small. Little benefit can be expected from this pro-
cedure, however, unless it is started before many of the birds have be-
come infected. The recovery of sick fowls may be hastened by irrigating
the nasal passages with liberal amounts of a dilute hypochlorite solution
or other nonirritating disinfectant. For this, a poultry nasal irrigator is
desirable. Severely affected fowls had better be destroyed at once.
Claims that increasing the vitamin A in the feed for a flock with in-
fectious coryza will lessen the severity and shorten the course of the
disease have not been substantiated by the results of experimental
studies. Such studies have shown that the resistance of chickens to the
disease may be enhanced by giving them amounts of vitamin A greatly
in excess of normal requirements for a few weeks before they are ex-
posed. No beneficial effect was demonstrated, however, when the feeding
of an excess of the vitamin was started at the same time as exposure to
the disease or after symptoms had appeared.
When the appetite of the flock is impaired, an endeavor should be
made to tempt the chickens to eat more by some modification of the feed-
ing practice. They may, for example, be offered a daily light feed of
moist mash, rolled barley soaked in milk, and fresh succulent greens.
60 University of California — Experiment Station
Sick chickens are not benefited by vaccination with avian mixed bac-
terin, by medication of the feed and drinking water, or by having
chemicals sprayed over them when they are on the roosts.
Other Comments. — It should not be inferred from the foregoing that
all coryza in chickens is caused by the infectious agents mentioned nor,
indeed, that all is infectious. Not infrequently failure results from
attempts to show that coryza, affecting an individual or a few birds of
a flock, is infectious and transmissible. A coryza of a noninfectious type,
however, is not likely to be persistent, nor is it likely to affect many birds.
It is probable that an exaggerated importance has been attached to
exposure of chickens to cold and dampness or faulty housing conditions,
such as draughtiness, poor ventilation, and overcrowding, as causes of
coryza. It is, nevertheless, well to assume that such unfavorable condi-
tions may be responsible for the disease, and that infectious coryza
would be more damaging under such circumstances. Therefore, it is
advisable to keep chickens inside during wet weather, and, whenever
coryza is seen, to correct at once any possible faults in housing condi-
tions that can be found.
In mild attacks of coryza, the possibility of vitamin-A deficiency
should be considered because a nasal discharge is a common and early
symptom of deficiency of this vitamin (see p. 100) . This could occur with-
out being suspected if vitamin A was being supplied principally by
alfalfa meal and the quality of this ingredient of the mash happened to
be poor.
Any case of coryza should be regarded as potentially dangerous and
the infected bird removed from the flock. If more cases appear, steps
should be taken to ascertain if infectious coryza is present. By so doing
the disease may possibly be headed off before it gets out of hand.
FOWL POX
Pox in birds has a world-wide distribution and a variety of bird hosts.
It is of greatest economic importance as a disease of chickens and turkeys
but is seen occasionally as a natural disease of pigeons and canaries. The
several cases of the disease in wild birds that have been seen in Cali-
fornia were apparently of chicken origin. Pox of chickens can affect a
wide range of domesticated and wild birds, exceptions being pigeons,
which are not affected by the chicken strain of the virus, and water
fowl. Outbreaks are most prevalent during the fall and winter but may
occur at any time of the year.
Cause. — Fowl pox is one of the group of diseases caused by the type
of infectious agents known as filterable viruses. The virus is present in
large amounts in the lesions which form on the skin. It is present in
Bul. 674]
Diseases of Chickens
61
blood and internal organs to a much less extent or not at all. This virus
survives for a long time on poultry farms and is resistant to disinfect-
ants. Consequently, it is very difficult to completely remove or destroy
the infective material remaining in a poultry house after an outbreak
of the disease.
Fig. 20. — Fowl pox in a cockerel; natural infection. (From Ext. Cir. 8.)
Symptoms. — The characteristic lesions are small wartlike growths on
the comb, wattles, and skin of the face (figs. 20, 21). They may also
occur on the feet and legs and any unfeathered area of the skin of
molting birds. The lesions begin as minute, smooth, yellow eruptions.
Their size rapidly increases, their surfaces become roughened and dry
and the color changes to dark brown. Within 2 or 4 weeks a dry scab
forms, loosens, and drops off. Individual lesions often join so that a
large area becomes solidly covered. Skin lesions are frequently accom-
panied by the formation of masses of soft, yellow, cheesy material or
canker on the mucous membrane of the mouth and eyes.
The effect of the disease on an individual is proportional to the extent
of the lesions. A few pocks on the skin dry and drop off without any
62
University of California — Experiment Station
appreciable effect on the general health. Extensive skin lesions and
canker, on the other hand, are more lasting and are accompanied by
depression, loss of appetite, emaciation, and, in many cases, eventual
death. Canker may interfere with consumption of feed or cause loss
of eyesight or death from suffocation.
Outbreaks of fowl pox vary greatly in severity. In some cases the
disease may be restricted to a few birds of a flock and cause little damage,
while in other flocks the lesions may be very severe; the disease may
spread through almost the entire flock and cause a great loss, both from
Fig. 21. — Fowl pox in a baby chick ; natural infection. (From Ext. Cir. 8.)
decreased egg production and from the death of the infected fowls. The
mortality is greatest when a large percentage of the infected fowls have
canker in addition to lesions on the skin. In many outbreaks in laying
flocks, the loss from decreased production of eggs is greater than from
death of chickens.
Chickens that recover from pox are solidly immune against reinfec-
tion, usually for life. Recovered fowls may be virus carriers, but for
how long and in what manner has not been definitely shown. Neverthe-
less, there is enough field evidence to indicate that it is unsafe to mix
susceptible chickens with those that have had fowl pox.
Diagnosis. — The appearance of fowl-pox lesions about the head is
usually so characteristic that one has little difficulty in recognizing the
disease. Skin lesions in other locations, and occasionally on the comb as
well, are less typical, and inoculation of susceptible chickens is necessary
to positively identify them. Doubtful cases should be submitted to a
diagnosis laboratory.
Bul. 674] Diseases of Chickens 63
Canker of unknown origin or resulting from irritation by particles of
litter or other foreign material which may become lodged in the eye or
the cleft in the roof of the mouth is often present in a few birds in any
flock. These are not likely to be due to fowl pox unless skin lesions of fowl
pox are also present.
Preventive Vaccination. — Vaccination of growing chickens to protect
them from fowl pox after they mature has been practiced for more than
twenty years and is now done routinely on many poultry farms.
ii,;, : .
B
Fig. 22. — Chorioallantoic membranes of chick embryos infected with pox
virus: A, membrane infected Avith pigeon virus; B, membrane infected with
chicken virus ; C, normal membrane. In making vaccine, the thickened area
of the membrane is dried and finely powdered.
The vaccine consists of lesions taken from the comb of artificially in-
fected young chickens or from the chorioallantoic membrane (fig. 22) of
chicken embryos on which the virus has been propagated by introduc-
ing it through a window cut in the eggshell (fig. 23). The source of
virus in vaccine is indicated on the label of the container by the words
"chicken origin," "chick-embryo origin," or "egg-propagated." The vi-
rus-bearing tissue is dried and powdered. For use in vaccination, the
powdered virus is mixed with sterile water, physiological salt solution,
or a solution of glycerin. This treatment does not influence the virulence
of the virus. The vaccine, therefore, is capable of causing severe fowl
pox and must be handled carefully and strictly in accordance with
instructions.
Vaccine prepared from pigeon strains of pox virus is also available.
This is to be used only when chicken-virus vaccine is contraindicated
(seep. 69).
Methods of Vaccination. — Chickens may be vaccinated with chicken-
virus vaccine by either of two methods, the feather follicle or the stick
method ; with pigeon-virus vaccine, by the former only.
64
University of California — Experiment Station
The feather-follicle method consists in applying the vaccine with a
small brush to a few feather follicles on the leg from which the feathers
have been plucked. When using chicken-virus vaccine not more than
four or five follicles should be exposed; for pigeon- virus vaccination
the number of follicles may be increased to from ten to twenty.
Fig. 23. — Incubating egg in which chicken-
pox virus is propagated. The seed virus is de-
posited on the chorioallantoic membrane which
surrounds the chick embryo and the window
is then rimmed with melted paraffin and sealed
with cellophane.
Fig. 24.-
-Types of instruments in common use for vaccinating
against fowl pox. (From Bui. 613.)
The stick method consists in making one or more pricks in the skin
with a sharp-pointed instrument immediately after it has been moistened
with vaccine.
A common place for vaccination by the stick method is the outside
of the upper end of the drumstick or on the breast. The feathers should
be parted to expose the skin before the "stick" is made. The points of
the vaccination instrument should be shortened to about % inch by
wrapping with tape or thread (fig. 24). This prevents too deep penetra-
Bul. 674]
Diseases of Chickens
65
tion of the points into the muscle tissue and also helps to insure introduc-
tion of vaccine into the punctures through the skin.
Another vaccination site is the web of the wing. Vaccination here is
done by piercing both layers of skin from the inside out with a needle.
Fig. 25. — A good instrument for vaccinating baby chicks, made by cutting
off the end of a large sewing needle through the eye and grinding sharp points
on the ends. A tiny drop of vaccine is carried between the two points. It is
fastened in a wood or metal handle or a cork. (Greatly enlarged.)
Fig. 26. — Vaccinating a baby chick in the skin of the flank anterior to the thigh.
One or two sewing machine needles attached to a suitable handle, as
shown in figure 25, make an excellent instrument. Vaccine carried by
both the eye and groove of the needle is quite certain to be deposited in
the skin punctures.
If baby chicks are to be vaccinated, the procedures vary from the
preceding only in that a single needle is used and the best vaccination
site is the loose fold of skin in the flank region, not the web of the wing
66
University of California — Experiment Station
(fig. 26). In some flocks of baby chicks vaccinated in the latter location,
many developed lesions about the head, and heavy loss resulted.
There appears to be little difference between the two methods of ad-
ministering chicken-virus vaccine either as regards efficiency in im-
munizing against the disease or effect on the general health of the fowls,
except that the stick method is the one to use for baby chicks. The choice
Fig. 27. — Takes from fowl-pox vaccination, by stick method with two
needles: A, on the web of the wing; B, on the breast. A also shows accidental
infection of a follicle from which a feather was pulled in vaccinating. Photo-
graphed on the eighth day after vaccination. (Actual size.)
of method, therefore, is largely a matter of personal preference on the
part of the fowl owner or of the operator. Pigeon-virus vaccine, as pre-
viously pointed out, must be administered by the feather-follicle method.
Failures to immunize a satisfactory percentage of chickens by vacci-
nation have resulted from attempts of users to stretch the vaccine by
vaccinating several chickens with a brush or sticking instrument before
again moistening it with vaccine, instead of moistening it between each
bird as directed. Such an attempt to economize may prove costly.
Effects of Vaccination with Chicken-Virus Vaccine. — Fowl-pox le-
sions or takes should develop at the site of vaccination in from 5 to 7
days and remain for 10 to 20 days (figs. 27 and 28). They can be easily
68 University of California — Experiment Station
detected by sight or feeling as hard nodules by the eighth to tenth day.
Takes from virus of chicken origin soon become dry scabs which loosen
and fall off. Lesions may develop on the head parts of a few chickens,
but these usually disappear quickly and harmlessly. Takes from egg-
propagated virus may disappear with slight or no scab formation.
Fowls may become somewhat listless and have a decrease in appetite
during the third or fourth week after vaccination. In flocks of young
fowls that were in good condition when vaccinated, this reaction may
not be seen at all or may last but a few days. The reaction is likely to be
less pronounced in fowls vaccinated before they are 3 or 4 months old
than in older ones. Healthy adult flocks that are vaccinated when they
are molting and laying very few eggs should exhibit little or no effect.
Fowls vaccinated when in poor condition as a result of intestinal
parasites, faulty management or feeding methods, or other causes, are
apt to have a very severe and prolonged reaction, which leads to con-
tinued poor appetite, emaciation, and often death of many birds.
An occasional flock of young birds apparently in good condition when
vaccinated suffers a severe vaccination reaction which causes death of
many birds and from which recovery is very slow. In some cases, no ex-
planation for the occurrence of a severe reaction under such conditions
can be found, but careful investigation is likely to reveal the presence
of an intercurrent disease.
Day-old-chick vaccination has been studied in controlled experiments
and practiced to a limited extent on farms. In many of the flocks on farms
no unfavorable effects were observed ; in other instances the results were
confused by the appearance of an intercurrent disease. In all controlled
experiments, growth of the chicks was definitely retarded by vaccination,
although in a number of experimental groups this would not have been
detected if the chicks had not been weighed at regular intervals and
their weights compared with those of nonvaccinated controls. The harm
to the chicks in such instances was not serious nor lasting. The effect of
infectious diseases, such as pullorum disease or cecal coccidiosis, however,
was much more severe among the vaccinated chicks than among non-
vaccinated controls.
The occurrence of colds, infectious laryngotracheitis, or other infec-
tious disease in flocks after vaccination should not be regarded as a
direct effect of vaccination or of the introduction on an infectious agent
with the fowl-pox vaccine, but rather to infection on the premises, to
which they would have been exposed and with which they probably
would have become infected whether or not they were vaccinated.
In pullet flocks whose egg yield has reached 10 to 20 per cent or more
and in flocks of older hens, egg production can be expected to be reduced
Bul. 674] Diseases of Chickens 69
and retarded for a period of 30 to 60 days, and the birds are liable to go
through a partial or complete molt. The egg production of pullets that
have just started to lay, however, is not so apt to be seriously influenced
by vaccination.
Fowls become immunized against fowl pox within 3 weeks after vacci-
nation. The immunity in most cases appears to be sufficiently lasting to
protect fowls against the disease for at least a year and usually for life.
Vaccination provides no protection against fowl pox for the first 2 or 3
weeks, and during this period will not check the spread of the disease in
an infected flock.
Vaccination is indicated:
1. As a routine preventive measure on any farm on which fowl pox
has occurred. Pullets (and cockerels to be kept for breeding) should be
vaccinated when they are from 1 to 4 months old. If cecal coccidiosis is a
regular visitant, it is best to wait until this is past and the flock is fully
recovered. When several lots of chicks are raised during a season, each
may be vaccinated separately as it reaches a suitable age. Vaccinated
and unvaccinated chickens, however, should not be kept in the same or
adjoining pens.
2. Routinely on any farm in a congested poultry district whether or
not fowl pox has occurred on it. This is advisable to avoid having the
disease to combat at a time unfavorable for vaccination. Each age group
of chickens can be vaccinated at the most propitious time.
3. For all new stock that is added to a vaccinated or previously infected
flock or that is to be placed in houses previously used for vaccinated or
infected chickens.
4. For day-old chicks as a routine control measure in broiler plants in
which fowl pox is appearing in the chicks before they reach the market
age.
Vaccination is not indicated :
1. For a flock affected with another disease.
2. For chickens in poor condition because of faulty management, in-
adequate diet, intestinal parasites, or other causes. In such a flock, vacci-
nation should be delayed until the cause of the poor condition is removed
and the chickens regain good health.
3. For the treatment of infected chickens.
4. For use on farms which are not near other poultry farms and on
which fowl pox has never occurred.
5. For performance by persons who are unfamiliar with conditions
under which it can be safely and effectively used.
Procedure and Care of Flocks after Vaccination:
1. At least 25 per cent of the flock should be examined for takes on the
70 University of California — Experiment Station
eighth to tenth day after vaccination. If a large majority of these do not
have definite takes, the entire flock should be revaccinated, or the entire
flock examined and those without takes segregated for revaccination.
2. Watch the flock carefully during the second and third weeks after
vaccination. If any indication of depression and decreased appetite is
seen, endeavor to increase food consumption by tempting the chickens
with moist mash, rolled barley soaked in milk, or other appetizing de-
partures from regular feeding practices.
3. When a severe reaction occurs after vaccination, have specimens
examined by a competent person to determine if there may not be some
complicating condition present which can be corrected.
4. If the reaction after vaccination causes a portion of the birds to
become weak and lose weight, separate them from the more vigorous and
thereby enhance their chances for recovery.
Some Precautions for Users of Vaccine:
1. If vaccine is used for a portion of a flock, vaccination of remaining
susceptible birds should follow soon afterwards.
2. Unvaccinated susceptible chickens should not be kept in quarters
previously used for vaccinated or infected chickens.
3. Vaccinated chickens should not be added to a susceptible flock until
2 to 4 months after vaccination.
4. Unvaccinated chickens should not be added to a vaccinated flock.
5. Owners of vaccinated flocks should advise purchasers that the
chickens have been vaccinated.
Vaccination with Pigeon-Virus Vaccine. — Pigeon-virus vaccine will
produce a take in chickens only when applied by the feather-follicle
method. A take consists of swelling of the infected follicles, which dis-
appears in a few days without scab formation.
There is no postvaccination reaction from this vaccine to cause de-
pression, loss of appetite, or decrease in the egg production of laying
chickens. Consequently, it has been recommended for emergency vacci-
nation of laying flocks.
The evidence concerning the effectiveness of this procedure is con-
flicting. Some reports indicate that an exposed laying flock or the still-
healthy birds of one already infected can be given protection quickly
enough and lastingly enough by pigeon-virus vaccination to ward off the
disease and carry the flock until it can be revaccinated safely with the
more effective chicken- virus vaccine. Other reports state that resistance
to fowl pox develops so slowly from pigeon-virus vaccination that the
procedure is of very questionable value. It is generally agreed that
pigeon-virus vaccination cannot be depended upon to give protection
for longer than about 6 months.
Bul. 674] Diseases of Chickens 71
Control of Outbreaks of Fowl Pox. — Sanitary measures that may be
used in an infected flock consist in (1) separation of the sick from the
healthy and transfer of the latter to freshly cleaned and disinfected
quarters; and (2) daily careful inspection of the flock and individual
examination at least once a week so that new cases may be detected and
removed early. By these measures it may be possible to so retard the
progress of the infection that there will never be a large number of
chickens affected at a time and the loss from mortality and decreased
egg production will be small. These measures are not likely to be effective,
however, if a fourth or more of the chickens are found to be infected at
the first examination.
Vaccination of birds not yet infected is a certain means of stamping
out an outbreak within 3 or 4 weeks. The fewer infected birds there are
before vaccination, the more effective is the procedure. For growing birds
or nonlaying adults, it can be adopted without hesitation. It should not
be adopted for a laying flock, however, without due consideration of the
possible adverse effect of vaccination on egg production. To the question
as to which will cause the greater loss, the effect of the disease or the
effect of vaccination on egg production, no definite answer can be given.
If the disease is of a mild form and continues to be, then the disease is
perhaps likely to be less costly than vaccination might be, while the
reverse is apt to be true if a severe form of the disease is present. Since
there are no definite criteria on which to base a recommendation, the
choice of procedure must be left to the flock owner.
Vaccination with pigeon virus would be safe, but, as pointed out in
the preceding page its effectiveness is somewhat uncertain.
Treatment. — Kecovery of infected chickens may be hastened by re-
moving the scabs and canker and applying tincture of iodine liberally
with a swab or medicine dropper. Particular pains should be taken to
remove all canker from the eyes by careful pressure and massage and
from in and around the opening into the larynx with forceps. Treatment
should be repeated every 2 or 3 days until definite regression of the
lesions is evident.
Medication of the feed and drinking water is valueless.
FOWL TYPHOID
Fowl typhoid is a widely distributed, acute infectious disease of
chickens and other species of birds. It also occurs as a localized infection
of hens and an acute disease of chicks which is much like pullorum
disease. In California, the acute infection of adults is seen more fre-
quently in turkeys than in chickens. This disease should not be confused
with the disease of chickens and turkeys known as "paratyphoid."
72 University of California — Experiment Station
Cause. — Fowl typhoid is caused by the bacterium Shigella galli-
narum. The germs are taken into the digestive tract with contaminated
food and drink. From here they may enter the blood stream, become
generally distributed in the organs, multiply, and cause death ; or they
may become localized in some organ and not affect the general health.
The germs are usually present in the intestines and are discharged from
the body with the droppings. The fowl-typhoid organism is closely re-
lated to the one which causes pullorum disease, and the effects of the
two on chickens may be much the same.
Symptoms. — Sick birds have no symptoms which are typical for the
disease. The feathers are ruffled, the wings droop, and the birds become
weak. Appetite is always reduced, but thirst may be increased. Diarrhea
is a common and often the most prominent symptom. The comb and
wattles are frequently pale, but may be congested and dark. Death
usually does not occur until after a few days of illness. Outbreaks may
follow a prolonged erratic course with few cases appearing at a time.
The lesions in dead birds are no more characteristic than the symptoms
of the sick. The changes sometimes found which are suggestive of fowl
typhoid are a watery condition of the blood, enlargement and dark red
color of the spleen, and enlargement and dark bronze color of the liver.
Infection, when localized in the ovary, produces changes in that organ
like those of pullorum disease (see p. 27).
Diagnosis. — Since recognition of the disease is impossible from the
appearance of sick and dead birds, a diagnosis can be made only through
bacteriological procedures at a laboratory.
Prevention. — Since fowl typhoid is a filth-borne disease, sanitary
measures are necessary for its prevention and control. Outbreaks of the
acute type of disease seldom occur in flocks that receive proper care and
are provided with sanitary surroundings.
In combatting an outbreak, sick birds should be removed, killed, and
burned, and the healthy confined to clean, disinfected houses. The litter
should be changed frequently and contamination of feed and water with
droppings prevented. A disinfectant may be added to the drinking water
to destroy any germs with which it may become contaminated (see p. 25) .
The yards should be thoroughly cleaned and not used again for several
months.
When there is localized ovarian infection, the disease may be trans-
mitted to chicks through the eggs. The problem of control is then the
same as for pullorum disease and the same measures apply (see pp. 31-
36 ) . Fortunately the fowl -typhoid and pullorum-disease organisms are
so much alike that the agglutination test for pullorum disease will detect
also the carriers of fowl typhoid.
Bul. 674] Diseases of Chickens 73
Treatment. — Medication of individuals or through the feed and water
cannot be expected to benefit chickens with fowl typhoid. Vaccination
with fowl-typhoid or avian mixed bacterin is of uncertain value for
either treatment or prevention.
FOWL CHOLERA
Fowl cholera may exist as an acute, rapidly fatal, infectious disease
or as a chronic infection which may produce a lingering, debilitating
disease or a localized disease process in some organ. All species of domes-
ticated birds are susceptible. In California as a whole, the disease is not
of great economic importance; but in certain areas of the state, it is
quite troublesome.
Cause. — The disease is caused by a species of bacteria named Pasteur-
ella avicida. The organism belongs to a group which infects nearly all
species of domesticated animals. The organism which infects one kind of
animal, however, is not likely to be infectious for another. Fowl cholera
is extremely virulent for small laboratory animals, especially the rabbit.
This characteristic is very useful for identifying the organism in the
laboratory.
The virulence of the bacillus for chickens may be so low as to be prac-
tically harmless or so great that a minute dose will produce rapidly
fatal disease. Strains of the organisms of low virulence maintained in a
laboratory, are apt to remain in that state; but on farms, through in-
fluences of which nothing is known, they may suddenly become highly
virulent. Consequently, infected farms may be periodically confronted
with extensive and highly fatal outbreaks and in the intervals between
enjoy complete freedom from the disease.
Symptoms. — The first indication of an acute outbreak frequently con-
sists in finding birds dead under the roosts or in the nests. As the disease
progresses, the virulence becomes less marked and fowls may linger
several days before death. The sick fowls are drowsy, their feathers are
ruffled, and some may become lame from infection of the joints. Some
fowls may survive in a nearly lifeless state for several days, during which
they become extremely emaciated. Diarrhea is a constant, although not
diagnostic, symptom. The outbreak is likely to terminate as suddenly
as it began.
Some of the survivors of an acute outbreak are likely to be healthy
carriers of the infection.
In less virulent infections, small but continuous losses may occur over
a period of weeks or months. The deaths may take place while the
chickens are still in good flesh or after a lingering illness with consequent
emaciation.
74 University of California — Experiment Station
Fowl cholera also occurs as a localized infection of some organ or
part, such as abscesses in various locations, inflammation and swelling
of the joints of the legs, infection of the middle ear, edema of the wattles
(see p. 75) , and infection of the nasal passages. The last two of these are
of some economic importance in California.
The lesions in dead chickens are neither constant nor characteristic.
The organs of chickens that die suddenly may show very little change.
A common and highly suggestive finding is very small, bright-red hem-
orrhagic spots on the surfaces of internal organs, particularly the giz-
zard and heart, and on the lining of the body cavity. Another is the
presence of numerous small grayish specks or minute areas of necrotic
tissue on the surface of the liver. Such lesions, however, are seen in other
diseases and are not diagnostic of fowl cholera. The lesions otherwise
consist of degenerative changes of the organs like those which may re-
sult from various other disease conditions. Yolk material, either in a
liquid state or of a cheesy consistency, may be found in the abdominal
cavity of laying hens that die from an acute attack of the disease. This
condition is discussed further on page 111, in the paragraph on ruptured
yolk associated with nonspecific disease of the reproductive organs.
Diagnosis. — A positive diagnosis of fowl cholera can be made only by
a bacteriological examination. Neither symptoms nor lesions are suffi-
ciently characteristic. When the presence of the disease is suspected,
specimens should be submitted to the nearest laboratory at once.
Prevention. — The prevention and control of fowl cholera must be ac-
complished by sanitary measures alone (see p. 22-25). The addition of
partly grown or adult chickens to farms free from fowl cholera should
be particularly avoided since there might be healthy carriers of the in-
fection among them.
When an outbreak occurs, the sick birds should be killed and burned,
the healthy confined to cleaned and disinfected houses, and strict sanita-
tion maintained. The yards should be well cleaned and chickens excluded
from them for a few months.
Since some of the survivors in an infected flock are likely to be healthy
carriers of the infection, measures like those for the prevention of in-
fectious coryza (see p. 58) should be adopted. This would apply either
after an acute outbreak or after nasal infection with a strain of the
organism of low virulence. The means for preventing fowl cholera when
it occurs as edema of the wattles are discussed on page 73.
Treatment. — There is no evidence that drugs of any kind, given in any
way, will benefit a sick bird or influence the course of an outbreak
through a flock. Neither can any good results be expected from the use
of vaccines.
Bul. 674] Diseases of Chickens 75
EDEMA OF THE WATTLES
Edema of the wattles, previously mentioned as sometimes accompan}--
ing infectious coryza (p. 55) and fowl cholera (p. 74), often occurs in-
dependently of those diseases. Chickens of either sex may be affected, but
it is of particular economic importance in breeding males. It has been
responsible for incapacitating many males after they reached maturity
and thereby, in many cases, has seriously interfered with a breeding-
program.
Cause. — The condition appears to be due to any one of several species
of bacteria. One of these, the fowl-cholera organism, has well-established
pathogenic properties for chickens ; the others are ordinarily harmless.
Injection of cultures of the organisms isolated from infected wattles has
given irregular results.
Symptoms. — The infection starts as a soft swelling of one or both
wattles, which gradually increases in size and becomes more firm. The
fluid in the wattle, at first clear and watery, soon thickens and becomes
yellowish. It continues to thicken until about the sixth or seventh day,
when it has changed to a solid, cheesy mass which can be cleanly removed
if the wattle is cut open. The latter then begins to shrivel and becomes
reduced to one-third or one-half its original size.
Affected birds become listless, lose appetite, and their weight rapidly
decreases. In this condition, if not isolated, they are objects of attack
by other males. A high percentage of birds so attacked are killed and
many of the others are so badly injured that their usefulness as breeders
is destroyed.
The course of the disease from the first symptom to recovery, as a
rule, is not more than 3 weeks. A considerably longer time is required,
however, for them to regain lost weight and become serviceable breeders.
Prevention. — This trouble can be easily avoided by cropping the
wattles of all males in the flock. This can be done at any time after the
cockerels are large enough for the first selection of those which are to
be retained as breeders. If performed early, the hemorrhage is less and
easier to control. The wattles can be cropped by simply cutting them off
with scissors or a sharp knife. It is better, however, to use heavy 10-inch
compression or Fergerson forceps. These are firmly fixed to the wattle
as near the lower jaw as possible and the wattle severed with scissors or
knife along the lower side. The forceps are left in place for a few
moments after the wattle is severed, and the cut surfaces dusted with
antiseptic powder. The use of forceps greatly reduces the amount of
hemorrhage ; in fact, they are almost a necessity to avoid fatal hemor-
rhage when the wattles of large birds are cropped. If any cases of edema
76 University of California — Experiment Station
of the wattles are present in the flock at the time of cropping, all in-
struments should be thoroughly disinfected between each bird. Failure
to do this may result in spread of the infection and heavy loss.
COLIBACILLOSIS
"Colibacillosis" is the term applied to disease conditions of chickens
which seem to be of an infectious nature but which yield only the colon
bacillus on bacteriological examination. This bacillus is a normal in-
habitant of the intestine and usually is harmless. But under certain con-
ditions, not at all understood, it appears to be able to invade the blood
stream and tissues and cause disease. Attempts to reproduce the path-
ological condition with which it was associated by injecting chickens
with cultures of the organism have seldom been successful. The pre-
sumption that it caused the disease condition with which it was associated
is based solely on its presence there.
Colibacillosis is seen principally in young laying chickens and in
young chicks. In the former, the disease may resemble fowl cholera so
closely that it would be mistaken for that disease if a diagnosis was based
on post-mortem findings alone. In such cases, the disease appears sud-
denly, causes the death of several chickens within a few days, and then
as suddenly ceases. For example, in an outbreak in 1938, 17 of a group
of 250 vigorous pullets died within 6 days, 12 of them during the first
2 days. The lesions found were fibrinous exudate in the heart sac, con-
gestion of and areas of degeneration in the liver, peritonitis, and rup-
tured egg yolk. None of the other pens of chickens on the premises were
affected at the time and there has been no recurrence. The course of the
disease may be more protracted and the losses relatively larger than the
case cited.
The disease in chicks has no special identifying characteristics. When
present, the losses are above normal but not disastrously high. The organs
of dead chicks are apt to show little change beyond some areas of degen-
eration in the livers of some. Flocks of chicks most likely to be affected
are those which are poorly housed, undernourished, or lacking in vigor
for some other reason.
There are no special measures for prevention and the control of out-
breaks. Good sanitation and proper nourishment and care should be
provided.
AVIAN TUBERCULOSIS
Tuberculosis, formerly plentiful in California and still very prevalent
in some sections of the country, is rarely seen here at present, and then
only in general farm flocks. The reason for the disappearance of tuber-
culosis from the specialized poultry farms in this state is probably related
Bul. 674] Diseases of Chickens 77
to the large percentage of the flocks which are replaced each year with
baby chicks. This keeps the average age of the chickens low and eliminates
the older birds which would be the most potent carriers and spreaders
of the infection. Improvements in sanitation have also undoubtedly
contributed much to the reduction of the disease.
Cause. — Tuberculosis is caused by the germ Mycobacterium tubercu-
losis. Filthy, damp, crowded houses and yards are favorable for the
perpetuation and spread of the infection but cannot initiate it.
BN-a
mJm
B^ ^L<i ' ^^tK^ttltk
■Hr ■'■■;•"' *^»^.'
■titK^B
R^_. \
w&^tA
Fig. 29. — Tuberculosis nodules on the liver and the intestines of a fowl.
(From Ext. Cir. 8.)
Symptoms. — Affected birds exhibit symptoms of infection only in the
advanced stages of the disease. Then they become emaciated, the comb
and shanks are pale and shriveled, and some are lame. Losses from this
disease do not often occur in birds less than one year old.
The lesions of tuberculosis consist of round yellow spots varying in
size from a pinhead to a pea in the liver and spleen, and nodules varying
in size from a pea to a small walnut on the intestines or on the membrane
which holds the intestines in place (fig. 29). Lesions also occur less fre-
quently in the kidneys, lungs, skin, and bones. For a definite diagnosis
the presence of the organism must be demonstrated in the lesions by
microscopic examination.
Tuberculosis spreads by fowls' eating substances, such as food and
soil, contaminated by the discharges from infected birds. The loss from
tuberculosis is not apt to be great at any one time, but it is constant and
becomes increasingly severe as time goes on.
78 University of California — Experiment Station
Control. — Observing strict sanitary precautions, keeping chickens of
different ages in separate pens, and disposing of all fowls when they
reach the age of 18 to 24 months should gradually reduce the amount of
the disease and eventually eradicate it. For immediate eradication, the
entire flock can be sold and the farm restocked with baby chicks. Houses
and equipment can be used again shortly after thorough cleaning and
disinfection. Yards, however, must not be used for about 3 months if
the soil is thoroughly dry and for from 6 months to as much as a year if
it is moist.
Another method of controlling tuberculosis is by means of the tuber-
culin test. This test is made by injecting a small amount of a test sub-
stance known as "tuberculin" into the skin of the wattle. If an injected
bird has tuberculosis, the wattle will swell. Repeated tests at intervals
of about 6 months are necessary to free a flock entirely from tuberculosis
by this method. After each test all reacting birds must be removed from
the flock and the houses given a thorough cleaning and disinfecting. Be-
cause of the expense involved, this test is recommended only for flocks
that are valuable as breeders.
LYMPHOMATOSIS
Lymphomatosis belongs to a group termed "neoplastic diseases" ; these
include all new growths, which are usually referred to as tumors. Because
of their insidious nature, the importance of neoplastic diseases is likely
to be underestimated. Generally deaths are not great at one time, but
the continued loss of individual chickens over the period of a year may
amount to a considerable number. Few poultry raisers are fully aware
of the extent of mortality in their flocks from this cause.
Neoplastic growths may arise in any tissue of the body, hence there
are many types. Lymphomatosis is by far the most important and fre-
quently encountered member of the group in chickens. Some types of
lymphomatosis are not universally considered as neoplastic, or tumorous,
growths. The general character of the disease resembles a tumor, how-
ever, and the two have other characteristics in common.
Tumors not related to lymphomatosis such as those of the connective
tissue, called "fibromas" or "fibrosarcomas," occur in widely distributed
parts of the body with considerable frequency and do not always impair
the function of the organ or tissue involved or the health of the bird.
Another such tumor of the intestinal tract, called "adenocarcinoma,"
is often encountered. Many other types of tumors of relatively little
economic importance are also found. An accurate diagnosis of most types
of neoplastic growths can be made only by microscopic examination of
the tissues.
Bul. 674] Diseases of Chickens 79
Lymphomatosis occurs in three types: 18 (1) neural lymphomatosis,
commonly known as fowl or range paralysis ; (2) visceral lymphomatosis,
commonly known as "big-liver disease" or simply "big livers" ; (3) ocular
lymphomatosis, commonly known as "blindness" or "gray eyes." The
three types of lymphomatosis differ only with respect to the organ or
tissue which is involved. Neural lymphamotosis indicates that nerves
are involved ; visceral, that an internal organ or tissue, such as the liver
or spleen, is affected ; ocular, that tissues of the iris of the eye are invaded.
These conditions are characterized by the infiltration of the tissues
with an abnormally large number of cells, the appearance of which is
like the lymphocytes of the blood. The effect of this infiltration is, first,
merely to displace the tissue cells; but, as the process progresses, the
tissue cells may degenerate and be replaced by the foreign cells and the
function of the organ or part be impaired or destroyed. The size of the
whole or a portion of the invaded organ is always increased. If the process
continues long enough, large tumorous masses are produced.
The disease is extremely plentiful and widely distributed. All three
types are commonly represented in an affected flock, with one of them
predominant. A single type or any combination of the three may be
found in one chicken. The relative amount of each in a flock may change
from year to year. Poultry raisers are most familiar with types 1 and 3
because of the ease with which they may be recognized. Lymphomatosis
is credited with being responsible for nearly half of the mortality among
young laying chickens.
Lymphomatosis is often discussed in the literature as a type of leucosis
or a part of the avian-leucosis complex. The term "leucosis" includes a
group of pathological conditions which are characterized by an enormous
increase in the numbers of certain types of blood cells, either in the blood
itself or in the tissues. The principal members of the group are termed,
according to the type of blood cell that is present, "erythroleucosis,"
"myeloid leucosis," and "lymphoid leucosis," which includes lympho-
matosis. Some investigators find the three conditions constantly asso-
ciated and, therefore, regard them as different expressions of one disease.
Others have found them occurring alone and accordingly are inclined to
view each as a disease entity. By some, erythroleucosis and myeloid
leucosis are considered to be identical and distinct from lymphomatosis,
and still others have expressed doubt that the three types of lympho-
matosis are related. Present knowledge of the problem is insufficient to
provide an explanation of these variable findings. It may be that the
18 A fourth type called "osteopetrosis" which affects bones and has been found in
a few California chickens is omitted because of its rarity thus far and also because
its relationship to the other three types of lymphomatosis has not been fully
established.
80 University of California — Experiment Station
various types do represent a single disease and that the differences in
manifestations are due to the existence of different strains which pro-
duce varying responses in chickens. Another possibility is that the asso-
ciation of various types in a flock represents the coincidental occurrence
of distinct diseases.
Lymphomatosis is very prevalent among chickens in California.
Erythroleucosis and myeloid leucosis, on the other hand, have been seen
but rarely and, up to the present, not at all in association with lympho-
matosis, and further discussion of them is, therefore, omitted in this
bulletin.
Cause. — Although there is a considerable accumulation of evidence,
gained both from field observations and experimental results, that
lymphomatosis is a transmissible disease, it cannot be said at present that
this is an established fact. The many reports of uniformly successful ex-
perimental transmission of the disease by some investigators are opposed
by the irregular or negative results of similar experiments by others.
Furthermore, none of this vast amount of research has succeeded in de-
termining the nature of the causative agent or stimulus of the disease.
Bacteria, as a cause, seem to have been definitely eliminated. Some evi-
dence of the presence of a virus has been advanced but this is still
inconclusive.
The genetic constitution of chickens has been clearly shown to have
an important influence on the occurrence of the disease. The effect of
the hereditary factor, however, is believed to be on the resistance or
susceptibility of the chickens. In other words, it is not the disease or the
causative agent that breeding chickens may pass on to their progeny,
but the relative ability of chickens to withstand the disease when they are
being kept in a given environment. Chickens which have high resistance
to the disease on one farm, however, may not exhibit that quality when
they or their offspring are taken to another.
The former belief that intestinal parasitism was a cause of neural
lymphomatosis or paralysis has been entirely discredited.
Symptoms of Neural Lymphomatosis. — Neural lymphomatosis may
affect nerves in any part of the body, and the symptoms are correspond-
ingly varied. In some cases, a single nerve is involved; in others, two or
more. The disease became known as "paralysis" because of the frequent
involvement of the sciatic and brachial nerves, which supply, respec-
tively, the legs and wings. The first indications of the affection of these
nerves are drooping of a wing or incoordinated movements in walking.
The latter is followed by lameness or limping and finally complete in-
ability of the fowl to stand (figs. 30, 31). The paralysis may be of either
one or both legs, but one leg is apt to be more severely affected than the
Bul. 674]
Diseases of Chickens
81
other. The majority of paralyzed birds have a good appetite and, even
though unable to stand, retain some ability to move their legs and make
vigorous efforts to move about. They assume various peculiar postures,
Fig. 30. — Seven-month-old pullet with paralysis. (From Ext. Cir. 8.)
Fig. 31. — Four-month-old pullet with paralysis. (From Ext. Cir. 8.)
two of which are illustrated in figures 30 and 31. Paralyzed birds lose
flesh, the combs become pale and shriveled, the shanks pale, and the
plumage rough and dirty.
Another manifestation seen in many nonparalyzed chickens is pro-
gressive emaciation, commonly termed "going light" or "fade-out," re-
sulting from involvement of the vagus nerve which supplies the gizzard,
intestines, and other vital organs. These symptoms, however, are due
just as often or more frequently to other causes, such as intestinal
parasitism.
82 University of California — Experiment Station
Twisting and jerking of the head and neck are seen when nerves in
the neck are affected, and an occasional case of spasmodic coughing has
been traceable to involvement of nerves going to the respiratory organs.
Affected nerves are enlarged (fig. 32) and, in many cases, the color
is yellowish or grayish. The fine lines, or striations, so clearly visible on
the larger normal nerves, are often obliterated. The enlargement is due
to infiltration of the nerves with lymphoid cells.
Fig. 32. — Dissection of fowl with paralysis showing (A) right sciatic nerve of
normal size and (B) left sciatic nerve greatly enlarged. (From Ext. Cir. 8.)
The duration of the disease from the onset of visible symptoms to
termination in death varies greatly. Paralysis of the legs may progress
from slight impairment in gait to complete prostration and death within
a few days. On the other hand, prostration may not occur until weeks
after lameness is observed. Likewise completely prostrated birds may
linger for days or* weeks if their appetites are not impaired and food
and drink are made easily accessible to them. Paralyzed birds that re-
main in a good state of nutrition sometimes may regain ability to stand
and walk in a normal or nearly normal manner for short periods. Yet
rarely, if ever, has permanent recovery been known to occur among birds
that have exhibited definite symptoms.
The incidence of neural lymphomatosis is highest in chickens during
the first year of life. Numerous cases may appear in an affected flock
throughout the first laying year. Extensive outbreaks in flocks as young
as 6 to 8 weeks have been reported. As a rule, the disease spreads slowly
and only a few chickens are affected at a time. The total number of cases
Bul. 674] Diseases of Chickens 83
may vary from a few to as many as 50 per cent of a flock during a period
of 4 to 8 months.
Symptoms of Visceral Lymphomatosis. — Visceral lymphomatosis does
not have any characteristic symptoms. Affected chickens may become
dull and lose flesh, and their combs pale, or they may appear healthy
right up to the time of their death.
A common post-mortem finding is an enormously enlarged, pale-
colored liver. Along with this, a similar change of the spleen is usually
seen and, in many cases, also of the kidneys (fig. 33). The surfaces of
the organs may be uniformly pale or mottled. The invading cells may
become concentrated in restricted areas to form yellowish or grayish
tumors, varying in size from very small to as large as a walnut (fig. 33) .
Grayish, tumorous enlargement of the ovary and diffuse or tumorous
thickenings of the membranes of the abdominal cavity are seen fre-
quently. The heart, lungs, and other organs and tissues may also be
involved. The disease may affect the whole or a part of one or more organs
at a time, with resultant enlargement of the organ, varying from slight
to enormous.
Visceral lymphomatosis has much the same age distribution as the
neural type, but its beginning tends to be a little later than the latter and
it is more prevalent in chickens more than a year old. Since the affected
chickens show no identifying symptoms before death, the actual amount
of this type of disease in a flock is usually unknown. The limited data on
this point, however, suggest that the incidence of visceral lymphomatosis
is likely to be as great as that of neural lymphomatosis.
Symptoms of Ocular Lymphomatosis. — Ocular lymphomatosis begins
with a change in the color of the iris of the eye from yellow, yellowish-
brown, or red, to gray. As the disease progresses, the pupil becomes con-
stricted and distorted, and loss of eyesight finally results. In some flocks,
this type of lymphomatosis is more plentiful than the others.
Diagnosis. — The definite identification of lymphomatosis must be
made by microscopic examination of affected tissue. After the presence
of the disease in a flock has been established, however, symptoms and
lesions are fairly safe criteria for a diagnosis.
Paralysis of the legs or wings, or lameness, can be diagnosed as neural
lymphomatosis only if an accompanying definite enlargement of the
nerves to the affected part is found. Neural lymphomatosis in other loca-
tions does not cause characteristic symptoms. These cases can be recog-
nized only by the demonstration of characteristic gross or microscopic
changes in the affected nerves at post-mortem examination. Microscopic
examination is necessary for the satisfactory diagnosis of any borderline
cases.
84
University of California — Experiment Station
Visceral lymphomatosis, as previosuly pointed out, causes no symp-
toms which are diagnostic aids. The finding, on autopsy, of a greatly
enlarged, pale liver, with or without an accompanying similar change of
Fig. 33. — Livers and a spleen of chickens with visceral lymphomatosis:
A, B, enlargement of liver from infiltration with lymphoid cells; C, liver with
tumorous type of the disease; D, normal liver shown for comparison; E,
lymphomatous spleen; F, G, normal spleens. (All about half natural size.)
the spleen or kidney, is likely to be an indication of this disease. Lesser
enlargement and tumorlike lesions of these or other organs require
laboratory procedures for identification. But, as previously indicated,
Bul. 674] Diseases of Chickens 85
one is justified in regarding these as lymphomatosis when they are found
in chickens of a flock in which the disease is known to be prevalent.
Marked grayness of the iris and distortion of the pupil of the eye are
reasonably certain to be due to lymphomatosis, especially when they
occur in a flock in conjunction with another type of the disease. The
diagnosis of a moderate degree of graying of the iris, however, should
be confirmed by microscopic examination of the tissue, since there are
heritable types of gray iris not associated with disease.
Transmission. — Although, as stated previously, the transmissibility
of lymphomatosis is not an established fact, there is both experimental
and field evidence which suggests the possibility that the disease may,
under certain conditions, spread to healthy chickens by contact with
diseased ones or with contaminated litter or other material. No one,
however, has demonstrated the manner in which a transmitting agent
might leave the body of a sick bird and enter that of a healthy one nor
the stage of the disease and age at which this might occur. Some hold to
the belief that chickens become affected early in life but that symptoms
may not be seen until months later. The idea that, like pullorum disease,
lymphomatosis may be transmitted through the egg has little supporting
evidence.
Prevention and Control. — While the transmissibility of the disease
under farm conditions is not definitely proved nor the manner in which
transmission might occur known, it, nevertheless, might be wise to adopt
in an affected flock the sanitary measures for combatting an infectious
disease. The removal of chickens as soon as they show symptoms and are
still in good flesh is desirable because their food value can thereby be
salvaged, and possibly the rate of spread may be retarded and number
of cases reduced.
At the present time, however, most reliance for prevention and control
must be placed on a program of selective breeding, based on the knowl-
edge of the hereditary nature of susceptibility and resistance to the
disease. The exact program must be varied in keeping with the nature
of the problem.
A breeding or commercial flock that is free from lymphomatosis should
have replacements only by stock produced on the farm. A commercial
poultryman could produce his own replacements by selecting and mating
the best chickens of his flock. An alternative would be to procure the
replacement stock from an outside source that is likewise free from the
disease. To find such a source, however, would be a difficult and uncertain
undertaking.
The proper program for an affected breeding flock is to build up a
population of resistant stock by discarding the families in which the
86 University of California — Experiment Station
most cases of the disease have occurred. Included in this program should
be the autopsy of birds that die so that all cases of lymphomatosis could
be detected. A less exact program, and one adaptable also to the type of
flocks which supply the bulk of the eggs to commercial hatcheries, con-
sists in using only old hens, and preferably old males as well, for the
production of hatching eggs.
Replacements for an affected commercial poultry flock should be re-
sistant stock from flocks in which the selective breeding program has
been followed. A commercial flock owner may produce replacements
himself by selecting and mating the best of the old birds of his flock and
hatching from them.
The inherited resistance of chickens to lymphomatosis cannot be relied
upon to protect birds under all circumstances. Under the conditions of
experimental transmission experiments and also the natural conditions
of a poultry farm, the amount of the disease in rigidly selected resistant
lines, after becoming progressively less from year to year, may suddenly
take an upturn. The reason for this is not understood. Therefore, the
adoption of a selective breeding program to produce a resistant stock
and the use of such stock for replacements on poultry farms does not
mean that all danger from lymphomatosis has been removed.
Treatment. — There is no method of treatment of chickens with lym-
phomatosis that is at all effective. Wheat-germ oil, reported a few years
ago to be effective for both treatment and prevention of the disease, has
been found to have no merit.
COCCIDIOSIS
Coccidiosis exists to some degree on practically all established com-
mercial poultry farms. It is best known to poultrymen as a disease of
chicks from 4 to 12 weeks old. It also, however, is a cause of loss among
chickens throughout the growing period and well into the first laying
year. According to the portion of the digestive tract involved, it is termed
"cecal" or "intestinal coccidiosis." This classification has replaced the
former, less appropriate one of "acute" and "chronic" coccidiosis.
Cause. — Coccidiosis is caused by protozoan parasites, microscopic in
size, which invade and multiply in the walls of the intestine and cause
extensive injury to the mucous-membrane lining. Various forms of mis-
management or poor feeding methods, or subjecting chickens to sudden
changes in temperature are erroneously believed by some to be primary
factors in producing the disease. The only possible relation of such
factors to coccidiosis is that they may lower the natural vigor and re-
sistance of the fowls to the effects of the parasites.
There are seven known species of the coccidial parasite which infect
chickens. One or more of these are present on practically all poultry
Bul. 674]
Diseases of Chickens
87
farms. The characteristics which distinguish the species one from the
other are the shape and size of certain of their developmental forms, the
portion of the intestine affected, the type of injury that they cause to the
lining of the intestines, and, in some instances, the symptoms produced.
A species of great economic importance, Eimeria tenella, is the cause
of the commonly occurring severe, acute infection of the ceca (blind
pouches of the intestines) of young chickens, sometimes referred to as
"bloody diarrhea."
Fig. 34. — Oocyst of coccidia parasite: left, as it appears in fresh drop-
pings; right, after sporulation. (Greatly enlarged.) (From Ext. Cir. 8.)
The six other species, Eimeria necatrix, E. maxima, E. acervulina, E.
mitis, E. praecox, and E. hagani, infect principally the small intes-
tines. E. necatrix causes a very severe and often devastating type of
disease. Fortunately it is not so plentiful on California poultry farms as
less harmful species. The effect of E. maxima, E. acervulina, and E. mitis,
the intestinal species of greatest economic importance in California, on
chickens is less severe, but the total loss is probably greater than from E.
necatrix because they are more widely distributed. E. praecox is of such
low pathogenicity that infection with it alone might pass unnoticed. E.
hagani is a recently isolated species, and little is known about its patho-
genicity and distribution.
Chickens acquire infection by eating material which has been con-
taminated by the droppings of an infected fowl. In the wall of the intes-
tines, the parasite undergoes various developmental changes, multiplies
to an enormous degree, and finally produces an egg form or what is
termed an oocyst (figs. 34 and 35). No further development or multipli-
cation can now take place in the fowl, and the oocysts are discharged with
Bul. 674] Diseases of Chickens 89
the droppings. The entire process of development and multiplication of
the parasite takes place within the cells which make up the lining of the
intestines. The effect of this invasion is to destroy the cells with resultant
sickness and, in many cases, death. In many instances the small blood
vessels of the intestinal lining are ruptured and fatal hemorrhage results.
The extent of the damage is in direct proportion to the number of oocysts
which are taken in at a time.
The oocysts in fresh droppings cannot produce disease but, if proper
conditions of temperature and moisture are provided, the oocysts un-
dergo a change known as sporulation (fig. 34) . It is the sporulated oocysts
that produce coccidiosis when eaten by a susceptible chicken. Four to
7 days after consumption are required for the parasite to complete
its developmental cycle and appear again as oocysts in the droppings
(fig. 35). If a fowl survives an attack for a few days, it will discharge
countless numbers of oocysts and thus expose others. Chickens which
survive severe acute infection with certain species of the parasite will
cease to discharge oocysts in a few days, while those infected with certain
other species of parasite or with light infection with any species may
continue to discharge oocysts for a considerable period. Coccidial oocysts
are very resistant to disinfectants and exposure to natural conditions
on poultry farms. They will survive for months in the soil of poultry
yards and in the houses. Consequently, after a farm is once infected, the
control of coccidiosis becomes a perpetual problem.
Chickens that survive heavy infection with any species of the parasite
or that are exposed to repeated small doses develop a resistance to fur-
ther infection with that species. The time required and the degree of re-
sistance depend upon the species and the numbers and frequency of
intake of the parasites. This resistance may amount to practically com-
plete protection against reinfection or it may be insufficient to prevent
reinfection but enough to protect the fowls from any appreciable injury
resulting therefrom. In the latter case, chickens may discharge oocysts
over an extended period, during which they are continuous sources of
infection of others. Fowls over three years old have been found to be
discharging oocysts with their droppings, although it is certain that they
were exposed to infection when they were much younger. An immunity
or resistance to one species of parasite does not protect against infection
with any one of the other six. Thus, for example, chickens that are re-
sistant to Eimeria tenella by reason of an attack of the cecal form of
coccidiosis are still fully susceptible to any form of intestinal coccidiosis.
Coccidiosis may be distributed from one poultry farm to another by
any of the methods of the dissemination of transmissible diseases dis-
cussed on page 22. The readiness with which distribution of the parasite
90 University of California — Experiment Station
takes place is illustrated by the frequency with which coccidiosis occurs
even among chicks that are reared in new houses, with new equipment,
on clean soil, and without contact with any other chickens. Infected
mature chickens are a likely means of bringing infection to new premises
and to young chickens on the same premises.
There is little evidence to support the contention of some that hatching
eggs laid by infected mature fowls are likely to be a source of infection
of chicks.
Fig. 36. — Chick with cecal coccidiosis. (From Ext. Cir. 8.)
Symptoms of Cecal Coccidiosis. — As previously stated, cecal coccidi-
osis is caused only by Eimeria tenella. It is usually seen in chickens from
4 to 8 weeks old, although outbreaks among younger or older ones are
not uncommon.
In many instances the first indication of the presence of cecal coccidi-
osis in a flock of chicks is droopiness of a few. The affected birds remain
close to the hover, do not eat, and stand with wings drooping, head drawn
in, and eyes closed for long periods of time unless disturbed (fig. 36).
Droopy birds may be seen for 2 or 3 days before any deaths occur.
The droppings of affected chicks frequently contain blood in amounts
varying from that sufficient only to tinge the droppings to enough to
give them the appearance of consisting entirely of blood. The bloody
droppings usually are seen in the early stages of an outbreak and often
are the first indication of disease observed. The sudden deaths in an
acute outbreak are due entirely to the loss of blood. If the bloody drop-
pings become mixed with the litter and are overlooked, severely affected
chicks may die suddenly without any symptoms having been noticed.
The ceca of chickens which die suddenly at the beginning of an out-
break are usually distended with blood. If the chicks survive a few days,
Bul. 674] Diseases of Chickens 91
the ceca contain yellow, cheesy cores (fig. 37) . These cores, in chicks that
survive, will become gradually reduced in size and be discharged. The
light-yellow, cheesy cores sometimes seen in chicks 1 or 2 weeks old are
not due to coccidiosis.
Blood in the droppings and bloody or cheesy cores in the ceca of fatal
cases are sufficient for a definite diagnosis of cecal coccidiosis. The pres-
ence in the droppings of brick-red or salmon-colored, fleshy material
Fig. 37. — Ceca of chick with coccidiosis.
(From Ext. Cir. 8.)
not definitely blood, does not signify coccidiosis, however, because this
type of material is frequently seen in the droppings of noninfected
chickens.
Deaths in acute outbreaks are most numerous during the first few
days, but sometimes continue for 2 or 3 weeks. Many of the survivors
may fail to regain normal condition, and never become profitable. The
loss from this source is occasionally as great as that from the early
mortality.
Coccidiosis is usually present in a flock for some time before it is dis-
covered. It will begin as a very light infection of a few with oocysts that
were present in the brooderhouse when the chicks were put in or that
were introduced from without. The infected chicks soon begin to shed
oocysts, which are picked up by others, and so the contamination of the
92 University of California — Experiment Station
quarters gradually becomes more concentrated. When proper sanitation
is maintained, the contamination may remain so low that none or only a
few of the flock will develop symptoms of the disease. On the other hand,
the contamination may become so heavy that chicks pick up numbers of
oocysts large enough to cause symptoms and death and an outbreak
begins. The initial number of severely affected and dead is determined
by the number that have already acquired massive infection, which is
naturally a variable quantity. The number of additional fatalities de-
pends largely upon the sanitary measures that are taken to prevent
massive infection of other chicks. In any case an outbreak will usually
run its course in a week or 10 days. The survivors of infection will, in
the meantime, have developed resistance to further infection, and thus
continuance of the disease is prevented. Because of this, coccidiosis is
termed a "self -limiting" disease.
The loss from cecal coccidiosis, however, is not alone from death. Many
survivors of heavy infection will be permanently stunted and not worth
keeping. Also moderate infection may occur without symptoms char-
acteristic enough to make the poultryman even suspect that coccidiosis
is present. In such cases, the chicks appear unthrifty; some become
droopy ; some will die ; and the dead do not have gross lesions indicative
of coccidiosis. Infection of this sort may persist and, in the long run,
cause greater loss than more severe infection. Therefore, specimens
should always be submitted to a diagnostic laboratory when several of
a flock of chicks become unthrifty and droopy from an unknown cause.
Prevention of Cecal Coccidiosis. — Economical and practical sanitary
measures offer to poultry raisers an avenue of escape from the enormous
losses that result from cecal coccidiosis. The sanitary measures are not
intended to eliminate the infection totally but rather to hold it down
enough to prevent great damage. The parasites are so widely distributed
that chickens are almost certain to pick up the infection sooner or later
and, therefore, exposure to mild infection early in life is preferable to
complete protection from infection. This enables the chickens to grad-
ually build up resistance against the parasite during the growing pe-
riod and makes rigid sanitary control unnecessary after they are mature.
This statement may suggest that some precaution should be taken against
making sanitation too effective. On the contrary, at the present time in
poultry districts there are few farms on which a carefully planned
and conscientiously executed program of sanitation will do more than
keep coccidial infection within safe limits. The essential measures that
should be adopted are given in the following paragraphs.
The brooder house and all equipment should be thoroughly cleaned
and disinfected before chicks are put in (see p. 15). It should have no
Bul. 674]
Diseases of Chickens
93
outside runs except sun porches with %- to 1-inch-mesh wire bottoms.
Droppings should not be allowed to accumulate on the supports for the
wire, on the wire itself, or underneath. Concrete yards are less desirable
than sun porches. When used, they should be cleaned at least once each
day or kept covered with litter, which is changed daily. The litter, how-
ever, would be objectionable during rainy or windy weather.
Fig. 38. — An example of sanitary drinking fountain and feed hopper with
wire-mesh floor around them to prevent access of the fowls to droppings.
(From Ext. Cir. 8; photograph by courtesy of L. Van Es, University of
Nebraska.)
The places within houses where coccidia collect in the greatest numbers
are around water and feed vessels, under hovers, and beneath roosts.
The chickens should be excluded from these sources of infection, after
they are 2 or 3 weeks old, by placing the water and feed vessels on frames
covered with wire mesh (figs. 3, 6, and 38) ; installing frames covered
with wire mesh beneath the hovers or removing the soiled litter from
beneath the hovers and replacing it with fresh once or twice each day ;
and placing wire netting under the roosts.
On badly contaminated farms, it may be necessary to cover from one
half to the entire brooder floor with wire-mesh frames in order to prevent
damaging coccidial infection. The wire must be kept free from litter and
accumulations of droppings or it will be valueless. The portion of the
floor not covered with wire should be swept and fresh litter put in at
intervals of not more than a week after the first 2 or 3 weeks.
94
University of California — Experiment Station
Feed containers and watering devices should be constructed so that
it is impossible for the chicks to deposit droppings in the feed or on top
of the containers (figs. 2, 4, 6, 38, and 39).
The houses should be kept dry and not overcrowded.
All of the foregoing sanitary measures should be adhered to as long
as the chicks remain in the brooder house.
Colony brooders in plots of growing green feed are reasonably safe,
provided there is enough land available so that any given area is not
used for more than one lot of chicks each year. The same precautions to
1 ■ y m w
* V If | '* " f J
Fig 39. — A feed hopper which prevents chicks from contaminating either
the feed or the top of the hopper with their droppings. The chicks are more
positively prevented from perching on the metal strip across the top if saw
teeth are cut in it. This hopper was especially designed for use in the pre-
vention of coccidiosis. (From Ext. Cir. 8; photograph by courtesy of L. Van Es,
University of Nebraska.)
protect the chickens from the places where contamination is likely to be
the most concentrated are taken as when brooding is in stationary houses
(fig. 40).
The outdoor or colony brooding units with wire-mesh floors are also
satisfactory provided the wire and its supports are kept clean.
Considerable study of the value of sulfur in the prevention and control
of cecal coccidiosis has been made at several of the agricultural experi-
ment stations. This work has shown that chicks could be protected against
artificial infection with sporulated oocysts by feeding mash containing
5 per cent or more flowers of sulfur for a few days before and a few days
after inoculation. Recently the Louisiana Agricultural Experiment
Station has reported a method for using sulfur in the prevention of the
disease on poultry farms. This is as follows : The chicks are grown in
confinement for at least 4 weeks. During this time the sanitary measures
previously described should be faithfully carried out. If the chicks are
then to be turned out on the ground, mash containing 5 per cent each
Bul. 674]
Diseases of Chickens
95
of flowers of sulfur and no. 10 charcoal is fed for 2 days before and 5
days after this is done. At the end of this 7-day period, the feeding of
an all-mash ration containing 2% per cent each of flowers of sulfur and
of charcoal is begun and continued until the chicks are 12 to 16 weeks of
age. The feeding of sulfur in this way is said not to be harmful to the
chicks.
Fig. 40. — An arrangement to prevent moist areas of soil and to protect fowls
from droppings around watering places. The soil beneath the slat platform is
removed to a depth of 2 feet and replaced by coarse gravel. Any type of water
container may be used. The platform should be of such size and shape that all
parts of the water container are at least 2 feet from its edge. The use of an arrange-
ment of this sort is of value in the control of chronic coccidiosis and intestinal
roundworms. Substitution of wire mesh for the slats would be an improvement.
(From Ext. Cir. 8.)
Control of Outbreaks of Cecal Coccidiosis. — When the presence of
cecal coccidiosis is discovered, the chicks should be confined in houses
equipped to maintain sanitation as recommended for prevention. The
litter on the portions of the floor not covered with wire mesh should be
changed daily for at least a week, and longer if indications of the disease
are still present. The daily change of litter removes most of the oocysts
present in the droppings of infected chicks before they have undergone
sporulation, or development to the infective stage, and thereby prevents
chicks from picking up massive doses of them. In many cases this rela-
tively simple procedure, when started promptly, is all that is needed to
keep fatalities in check until the outbreak is terminated by the self-
limiting nature of the disease.
The feeding of mash containing 40 per cent dry skim milk as an
adjunct to sanitation is considered beneficial. This has a marked laxative
96 University of California — Experiment Station
effect and, therefore, should be fed only a few days. Daily change of the
litter is necessary to keep the floor dry. Thirst is increased and so the
chicks should be given ample facilities for drinking. If mash and grain
are fed, the amount of the latter should be restricted to from one third
to one half of the amount of mash consumed. Dried whey may be sub-
stituted for dry skim milk ; but because of its higher milk-sugar content,
the percentage in the mash is 32 instead of 40 per cent. A formula that
may be used for home mixing is : dry skim milk, 40 per cent, or dried
whey, 32 per cent ; wheat bran, 10 per cent; ground yellow corn, 30 per
cent; ground barley, 20 per cent with milk or 28 per cent with whey.
Forty per cent milk mash is obtainable ready-mixed at many feed
dealers.
The way in which the milk-mash benefits the chicks is not definitely
known. Some give credit to the milk-sugar content of the milk, some to
the nutritional value of the milk, and others to the laxative effect. Those
who hold to the latter believe that other laxative foods or drugs would
be just as beneficial.
Molasses has been used to some extent as a laxative substitute for milk.
There appear to be no experimental data to support this practice. It is
usually given as "molasses-bran," a mixture of 15 to 20 parts of molasses
with 80 to 85 parts of bran. This is substituted for the mash for half-day
periods. Another method of giving molasses is to add 1 cup to each 2
gallons of drinking water.
A method given by the Louisiana Agricultural Experiment Station
for using sulfur in the control of outbreaks of cecal coccidiosis is as
follows : As soon as symptoms appear feeding of an all-mash ration con-
taining 5 per cent sulfur and 5 per cent no. 10 charcoal is started and
continued for the following 7 to 14 days. If the weather is cloudy or if,
for any other reason, the chicks do not have at least 30 minutes' exposure
to direct sunlight each day, the amount of fish oil or other source of
vitamin D in the ration should be increased. (One-half pound of fish
oil containing 400 A.O.A.C. chick units per gram is said to be ample
for 100 pounds of feed. ) The medicated mash may be discontinued after
7 days if the outbreak has subsided. Feeding for the 14-day period, how-
ever, is said to protect chicks for a longer period and to have no harmful
effect if properly done. The recommendations state that sulfur is in-
tended as an aid, not a substitute for sanitary measures and that the
latter should be just as rigidly adhered to as if no sulfur were fed.
The results of recent experiments indicate that certain members of the
sulfa group of drugs, sulfaguanidine in particular, may be of value in
treatment of infected flocks. Thus far, however, the drugs have been used
only for treatment of artificially produced cecal coccidiosis and, there-
Bul. 674] Diseases of Chickens 97
fore, their effectiveness in outbreaks of the natural disease on farms is
not known.
All other attempts to find an effective medicinal treatment for the
disease have been fruitless. The drugs and chemicals that have been tried
include hydrochloric acid, catechu, mixtures of bichloride of mercury
and sulfocarbolates, potassium dichromate, ipecac, and bismuth sub-
nitrate.
Symptoms of Intestinal Coccidiosis. — Intestinal coccidiosis is seen
most commonly in chickens between the ages of 4 and 8 months, but
it frequently persists throughout the first laying year. Chickens with
massive infection with one species of the parasite, Eimeria necatrix, have
bloody droppings and may die after a brief illness. Exceedingly massive
infection with one other species, E. maxima, may likewise be rapidly
fatal, but in this case characteristic symptoms are lacking. Acute out-
breaks or even acute cases, however, are relatively infrequent ; instead,
the disease is of a lingering, wasting nature, manifested by decreased
egg production of laying birds, reduced appetite, roughened, dirty
plumage, paleness of the comb and wattles, gradual loss of flesh, and
weakness. Death occurs only after several days or even weeks of sickness.
Such symptoms would accompany any debilitating disease. The disease
may progress so slowly and cause marked symptoms in so few that the
presence of a dangerous infectious disease is not suspected. The ultimate
loss from retarded development of pullets, reduced egg production, and
numbers of worthless culls may, however, be as great as from an acute
type of infection or even greater.
The changes found on autopsy of dead birds are confined to the inside
of the intestines and vary according to the species of coccidia present.
They may consist of any one or any combination of the following : vary-
ing degrees of inflammation (reddening) in any portion; thickening of
the intestinal lining and the presence of excess amounts of thick, slimy
mucus ; small, round gray specks (aggregations of coccidia) or red specks
(small hemorrhages) in the wall of the intestine, visible from within or
without and most numerous in the middle and lower portion ; a diffuse
thickening and spongy appearance of the lining of the intestines. In
severe Eimeria necatrix infection, the intestine is ballooned and filled
with blood and bloody mucus. Such cases are rarely seen. The gray or
red specks in the intestinal walls are fairly typical of coccidial infection,
but they and the other changes named can result from other causes;
consequently, one is not usually able to identify intestinal coccidiosis
without the aid of a microscope. When chickens in a flock of pullets ex-
hibit any of the symptoms or lesions described above, it is advisable to
submit specimens to a diagnostic laboratory.
98 University of California — Experiment Station
Prevention of Intestinal Coccidiosis. — Sanitation is applied in the
prevention of intestinal coccidiosis with the same object as for cecal
coccidiosis, that is, to so restrict exposure of the chickens to the parasite
that they will not become harmfully infected and will be given an oppor-
tunity to develop protective resistance.
The measures to be employed are like those advocated for cecal coccidi-
osis and need not be repeated in detail. The weekly change of litter should
be continued until the chickens are 8 or 10 months old and longer if any
clinical cases of the disease are discovered. Emaciated birds should be
regularly checked for coccidial infection by a laboratory examination.
Confinement to houses and sun porches should be continued throughout
the first laying year ; after that, danger from the disease is usually past.
The sanitary measures for the prevention of the introduction of in-
fection on a farm should be faithfully followed (see p. 22).
Control of Intestinal Coccidiosis. — When evidence of the presence of
a considerable amount of the disease is discovered, the flock should be
immediately confined to the house and allowed no outside run except
a sun porch. The house should be cleaned daily for about a week. After
the first thorough cleaning, a small amount of litter should be used so
that it can be easily swept up with a broom. Birds should be excluded
from droppings boards by wire netting. The roosts and walks in front
of nests and feed hoppers should be swept clean daily. Wire-mesh plat-
forms should be installed around feed hoppers and watering devices and
be kept free from litter. Visibly sick chickens should be removed from
the main flock so that they may have a better opportunity to recover.
Any modification of feeding methods that may increase the appetite
should be tried. Sometimes a moist mash, frequent feedings of small
amounts of fresh, tender greens, or a daily feeding of rolled barley
soaked in milk will accomplish this. If the flock continues to show evi-
dence of the disease after a week, the daily change of litter should be
continued a little longer. When this is no longer necessary, a weekly
schedule of litter change should be adopted. Milk mash, drugs, and
chemicals have not been found of value as an adjunct to sanitation in
the control of intestinal coccidiosis.
MYCOSIS OF THE CROP
Mycosis of the crop is a common cause of losses in turkeys from 2 weeks
to 5 months old, but is of rare occurrence and of little economic impor-
tance in chickens. The only reason for including it in this bulletin is
that the disease is said to be the cause of unthrifty condition and greater
than normal mortality in numerous flocks of chicks. The field diagnosis
of mycosis in such cases can seldom be confirmed by laboratory examina-
Bul. 674] Diseases of Chickens 99
tion. The condition called "gizzard ulcers" or "erosions" is commonly but
mistakenly considered to be due to mycosis.
Cause. — The disease is caused by a fungus called Monilia albicans, and
usually occurs in company with some other debilitating condition. The
organism, therefore, appears to have low virulence for chickens and is
not likely to cause any disturbance in a well-nourished, vigorous flock.
The exact source of infection in a flock usually cannot be determined.
Symptoms. — Affected chicks do not show any specific symptoms. They
become listless, eat little, lose flesh, and the feathers are dirty and rough.
There is a small daily loss from death.
The lesions found at autopsy are usually confined to the crop. The
mucous membrane is thickened, rough, and dull, and may be covered
with a dirty white, false membrane. The organism can be demonstrated
by microscopic examination of scrapings from the crop lining. A positive
diagnosis cannot be made in any other way.
Prevention. — Mycosis is unlikely to occur in any flock of chicks that
is raised in reasonably sanitary surroundings and fed a proper diet.
When the disease has been diagnosed, the chicks should be confined
in clean, disinfected houses. Daily cleaning of the floors, feed hoppers,
and water vessels should be practiced for at least a week and longer if
conditions warrant. The smallest, poorest birds should be killed and
burned. The diet should be carefully investigated and any deficiencies
found, corrected.
The substitution of a 1-2,000 copper sulfate (bluestone) solution for
all drinking water for several days is an aid in control. A solution of this
strength is not poisonous but is sufficiently distasteful that chicks will
not drink it if other water is available. It should be put in crockery or
wood containers. A convenient method of making it is as follows :
For the stock solution dissolve 1 pound of copper sulfate in 1 gallon of soft water
or of hard water to which 1 teaspoon of hydrochloric acid or 1 cup of vinegar has
been added. Heat may be necessary to completely dissolve the copper sulfate. Store
in a glass jar or a crock. To make a 1-2,000 solution, add 1 tablespoon of the stock
solution to each gallon of water.
Use the solution in place of drinking water for at least a week after
improvement of the flock is noted.
INFECTION OF CHICKENS WITH HUMAN AND EQUINE VARIETIES
OF SLEEPING SICKNESS 19
It has been found recently by investigations conducted at the Hooper
Foundation that the viruses of western equine encephalomyelitis (a
variety of sleeping sickness of horse and man) and of St. Louis en-
19 Contributed by Win. D. Hammon of the George Williams Hooper Foundation for
Medical Research, University of California.
100 University of California — Experiment Station
cephalitis (a variety of sleeping sickness of man) are common infections
of chickens as well as other domestic animals, in certain of the valley
areas of California and the Yakima Valley of Washington. To a lesser
extent, other birds are affected. In chickens and most other animals,
the infection usually takes place without visible or recognizable symp-
toms, but it can readily be detected by blood tests or tests of the brain
and spleen. The virus of the eastern type of equine encephalomyelitis,
however, may produce visible illness and even death in some chickens.
There is apparently little or no danger that these diseases may be trans-
mitted to man or horses through contact with infected chickens or to
man through consumption of them when cooked ; but that they serve to
infect mosquitoes appears probable. From the high rates of infection
in chickens, as demonstrated by blood tests, and the rare infection of
man, it appears probable that the insect which is responsible for trans-
mission prefers the blood of lower animals to that of man, in most in-
stances. We have much more to learn of these infections in relation to
lower animals and man, but in certain areas where environment is suit-
able and the insect vector and virus are present, it has been established
that infections occur in many domestic animals.
NUTRITIONAL DISEASES
The diseases discussed in this section are those related to known dietary
deficiencies which occur on poultry farms. 20 Those that are seen only in
chickens on experimental diets are omitted. The investigations of nutri-
tional diseases thus far have been concerned principally with deficiencies
in the diet, leaving the field of the pathological effect of excess amounts
of food constituents largely unexplored.
VITAMENT-A DEFICIENCY
Disease results when the intake of vitamin A by the fowl becomes less
than is necessary to maintain health. In its early stages or in case the
deficiency is only partial, the manifestations are indistinguishable from
those of coryza, or colds. This symptom is so constant that the disease
became known as "nutritional roup." If the ration provides very little
or none of the vitamin or if a partially deficient ration is fed over a long
period, very characteristic symptoms and lesions develop.
Symptoms. — The symptoms are decrease in appetite; weakness and
emaciation; droopiness (fig. 41) ; reddened and watery eyes which may
be followed by the formation of an adherent white film over the third
20 For a more complete discussion of dietary deficiencies, the reader is referred to :
Almquist, H. J., W. E. Newlon, and T. H. Jukes. Feeding chickens. California Agr.
Ext. Cir. 108:1-41. Eevised 1940.
Bul. 674] Diseases of Chickens 101
eyelid and a mass of white cheesy material within the eyelids (fig. 44) ;
the formation of yellowish-white, round, cheesy, pustulelike patches
about the size of a pinhead in the mouth and throat (fig. 42) ; and oc-
casionally the formation of masses of white, cheesy material in the cleft
or elsewhere in the mouth.
Post-mortem examination of birds usually shows the kidneys to be
very pale and marked with a network of very fine white lines (fig. 43).
Fig. 41. — Typical appearance of fowls with vitamin-A deficiency.
(From Ext. Cir. 8.)
Occasionally a deposit of a white material is also found on the surface
of the liver, on the membrane around the heart, or elsewhere on the
surface of the organs.
Prevention and Control. — The common sources of vitamin A for
poultry are any kind of fresh greens, dried greens such as alfalfa meal,
yellow corn, and fish oils. The disease will not occur in chickens whose
diet contains an adequate amount of vitamin- A-carrying ingredients of
good quality. When fresh greens are fed and there is an abundant year-
round supply, an adequate amount of vitamin A is assured. Alfalfa meal
and fish oils are less certain sources because the vitamin A is so easily
destroyed by exposure to air, particularly in warm temperatures. Thus
a large part of the vitamin A in alfalfa may be lost by improper curing,
and the vitamin A in fish oil and alfalfa meal tends to diminish after
these ingredients are mixed in the mash. Consequently only fish oils and
102
University of California — Experiment Station
Fig. 42. — An advanced case of vitamin-A deficiency, showing the pharynx and
esophagus studded with pustules. (From Ext. Cir. 8.)
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Diseases of Chickens
103
Fig. 43. — Kidneys of a fowl with vitamin- A deficiency. (From Ext. Cir. 8.)
104
University of California — Experiment Station
alfalfa having a guaranteed minimum vitamin-A content should be
used, and these should be stored so that they are protected as well as
possible from exposure to air and warm temperatures and added to mash
in relatively small batches.
Flocks or fowls suffering from vitamin-A deficiency recover very
quickly when their intake of material supplying the vitamin is increased.
It is better to feed fresh greens than to add alfalfa meal or cod-liver oil
Fig. 44. — Cheesy material in the eye of a fowl with vitamin-A deficiency.
(From Ext. Cir. 8.)
to the mash, because the appetite of the chickens is impaired and they
will eat fresh greens more readily than mash. Very sick birds will re-
spond rapidly to individual dosing with 15 to 30 drops of a good fish oil
daily.
VITAJMIN-D DEFICIENCY (RICKETS)
Rickets is a disease of the bones of growing chickens caused by a defi-
ciency of vitamin D in the diet. This vitamin can be replaced by ultra-
violet light rays. These rays are found in sunlight and can be produced
artificially by mercury-vapor or carbon-arc lamps. The effect of these
rays is to convert substances in the skin to vitamin D. When this vitamin
is absent, calcium and phosphorus are not adequately deposited in the
bones.
Bul. 674]
Diseases of Chickens
105
The symptoms of rickets in young birds are poor growth, weakness of
the legs (fig. 45) , a stiff-legged gait, and swelling of the joints. "Beading"
of the ends of the ribs is a particularly characteristic lesion. Laying hens
without adequate vitamin D will continue to lay eggs, but since they
cannot utilize the calcium in their diet, will take calcium from their
bones in order to make eggshells. This is often the cause of crooked breast
bones in good layers.
Fig. 45. — These birds were raised together in a well-lighted house and fed the
same ration. The one on the left was placed in a box outside in the sunshine for
about an hour each day. The one on the right received sunlight only through a
glass window. This is a pronounced case of rickets. (From Ext. Cir. 8.)
If chickens have abundant exposure to direct sunlight, no provision
for vitamin D in the diet is required. Sunlight coming through a glass
window is valueless, however, because ordinary window glass filters out
the ultraviolet rays. Young chickens that are confined to the houses a
considerable portion of the time because of cool or rainy weather and
whether confined or not, during prolonged periods of cloudiness or f oggi-
ness, need a vitamin-D supplement in the ration. It is best to supply vita-
min D routinely in the diet of chicks for at least the first 2 months of
their life.
Fish oils are the best sources of vitamin D for chickens. They are now
marketed in containers which give the vitamin-D potency of the oil on
the label in terms of units of the vitamin per gram of oil. Directions for
use are given on the label and should be followed. When the oil is used
106
University of California — Experiment Station
to control rickets already present, a considerably larger amount should
be used than is necessary for healthy chicks, until definite improvement
of the chicks is seen.
Synthetic vitamin-D-bearing preparations of known potency may be
substituted if fish oil is unobtainable.
RIBOFLAVIN (VITAMIN G) DEFICIENCY
Riboflavin is one factor of what is known as the vitamin-G complex.
The term "vitamin G," however, is now commonly used with reference to
this factor alone. Riboflavin is a yellow pigment that is present in several
Fig. 46. — A chick afflicted with curled-toe paralysis
caused by an inadequate supply of riboflavin in the diet.
Note the typical posture and the inwardly curled toes.
(From Ext. Cir. 108.)
natural foodstuffs. The requirement of chickens for this vitamin is very
high. A deficienc}^ of it may cause a characteristic condition known as
"curled-toe paralysis" (fig. 46), and also slow growth and poor utiliza-
tion of food. A deficiency in the diet of breeders causes poor hatchability
of eggs.
The prevention and control of riboflavin deficiency naturally consists
in feeding an adequate amount. Good natural sources are fresh and dried
greens, dried milk, and dried whey. Cereals supply some of the vitamin
but are considered poor sources. Pure, undiluted dried yeast is an excel-
lent source but is too expensive. Its use for a limited period to bring a
badly deficient flock back to normal may, however, be advisable. Un-
diluted liver meal is another good source. The requirement of chickens
for riboflavin is so high that it may be impracticable to supply the entire
need from one source ; consequently, it is customary to use both alfalfa
meal and dried milk or whey in poultry rations.
Bul. 674]
Diseases of Chickens
10'
PANTOTHENIC ACID (FILTRATE FACTOR OR ANTIDERMATITIS
VITAMIN) DEFICIENCY
Pantothenic acid is another factor of the vitamin-G complex which
is required by chicks. Symptoms of a deficiency of this vitamin are in-
crustations at the corners of the mouth; thickening of the edges of the
eyelids, which tend to stick together ; ragged, brittle feathers ; and re-
tarded growth (fig. 47) .
Fig. 47. — A chick suffering from dermatitis caused by a
lack of pantothenic acid (the filtrate factor, or antidermatitis
vitamin) in the diet. Note the incrustation at the corners of
the mouth and tightly stuck eyelids. (From Ext. Cir. 108.)
Disease from a deficiency of this vitamin can be avoided and corrected
by supplying an adequate amount of it in the ration. The richest natural
sources of pantothenic acid among ordinary poultry foodstuffs are cereal
grains and wheat bran ; consequently, all chick rations should contain
as much of these ingredients as practicable. Cane molasses is another
good source which may be regularly incorporated in chick rations as a
preventive or added to the ration when symptoms of a deficiency are
seen in a flock.
Symptoms of deficiency are seen in some flocks which are fed a diet
which should supply an adequate amount of the vitamin. These occur-
rences are sometimes difficult to explain but may be related to the diet
of the parents of the chicks or to feeding methods. The usual diets of
breeding chickens are apparently never sufficiently lacking in panto-
thenic acid to affect health or hatchability of eggs, but, if they provide
108 University of California — Experiment Station
only a small amount of the vitamin, the chicks will have no reserve store
at hatching. Such chicks may not take in enough of the vitamin during
their early life to ward off a deficiency even though their diet would
be adequate under ordinary circumstances. Similarly, when the diet is
mash and grain which contains enough of the vitamin when the two are
consumed in proper portions, some chicks may eat mash almost exclu-
sively and thus not get enough of the pantothenic-acid-bearing cereals.
In such cases, there would be a few cases of pantothenic acid deficiency
in an otherwise healthy flock.
GIZZARD EROSIONS
Gizzard erosions, also erroneously called "gizzard ulcers," are seen
in many flocks of young chicks. The erosions consist of patches of the
gizzard lining which become discolored and roughened, and finally
disappear.
The condition results from a deficiency of a necessary dietary in-
gredient termed the "gizzard factor," which in some way reduces the
production of bile. It is not caused by the fungus infection of the crop
and gizzard known as "mycosis" (p. 98).
Gizzard erosions do not appear to retard growth nor to otherwise affect
the health of the chicks. They tend to disappear as the age of the chicks
increases, perhaps because the need for the gizzard factor becomes less.
When found in undersized and unthrifty chicks, as they frequently are,
the gizzard erosions must not be regarded as the cause of the poor
condition of the birds. The conditions responsible for the sickness of
the chicks, however, may indirectly have increased the severity of the
gizzard erosions.
The gizzard factor is present in a number of poultry foodstuffs, in-
cluding fresh and dried greens, wheat bran, rice bran, hempseed meal,
and soybean meal. Kale is a better source than alfalfa. The factor can
also be supplied by substituting a liquid milk product, that is, skim milk,
buttermilk, or whey, for the drinking water. Dried milk products, how-
ever, are ineffective. Gizzard erosions will usually be prevented by a
ration containing 5 per cent of a good grade of alfalfa meal and 15 per
cent of wheat bran. The feeding of granite grit is also an aid in prevent-
ing gizzard erosions. When the trouble is known to be present in a flock,
it may be advisable to enrich the diet with the protective foodstuffs.
PEROSIS (SLIPPED TENDON)
Perosis, or slipped tendon, is a disease seen principally in young
chickens in poultry establishments, such as broiler plants, in which the
birds are raised in batteries or pens completely floored with wire mesh.
Chickens raised by ordinary methods are seldom affected.
Bul. 674] Diseases of Chickens 109
The condition, a permanent deformity, starts as a swelling around
one or both hock joints. In a few days, the shank becomes turned outward
and bent, and later the tendon may slip from its normal position over
the back of the hock (fig*. 48) .
Fig. 48. — An example of slipped tendon. The tendon of the bird's right leg
(on the left in the photograph) has slipped outwards from the normal position,
which bends and cripples the leg. The left leg is not affected. (From Ext.
Cir. 108.)
Affected chickens show no other abnormality and if able to get enough
food remain in fairly good flesh.
The factors which cause it are varied and the severity or prevalence
of the disease in a flock is proportional to the number of these factors
which operate together. Dietary factors are a deficiency of manganese,
a deficiency of choline, too much phosphorus, and perhaps, also, too much
calcium. Another factor is hereditary ; this causes heavy breeds to be
more susceptible than Leghorns. A fifth known factor is confinement on
wire floors, but this is not so potent as the absence of dietary factors.
A deficiency of manganese in the diet of breeders results in deformity of
chick embryos.
Perosis can usually be prevented by avoiding the use of too much bone
meal and of meat and bone scraps which contain large amounts of ground
bone, and also by the addition of V2 pound of dry manganese sulfate to
110 University of California — Experiment Station
each ton of mash. The addition of the manganese, however, will not com-
pensate for errors with respect to other components of the mash. Diets
ordinarily used are not likely to be deficient in choline.
NONSPECIFIC DISEASES
This section is included for the purpose of calling attention to the
importance of the large group of varied pathological conditions which,
as far as is known at present, are unrelated to any infection or parasitism
or to nutritional and genetic factors. There is no definite knowledge
concerning their cause or of measures for their prevention.
No one of these conditions by itself is likely to cause a large number of
deaths in a flock, but the data which have been collected concerning them
indicate that together they are probably responsible for nearly half of
the mortality and for a fourth or more of the culls among birds of laying
age on the average poultry farm.
Considerable information concerning the relative frequency of the
different types of nonspecific disease conditions, their distribution in
the body, and the age distribution has been obtained by the systematic
autopsy of the dead and culls on commercial poultry farms and in the
flock of the Division of Poultry Husbandry of the University of Cali-
fornia. The data show that the anatomical systems most frequently in-
volved were, first, the reproductive organs, second, the digestive organs
(including the liver) and, third, the kidneys. Taken together, these com-
prise more than 80 per cent of nonspecific diseases. Disturbances of
the digestive system were the most prevalent in hens under a year old,
those of the reproductive organs thereafter. Kidney involvement had no
marked age preference. Nonspecific disease was less prevalent among
hens under a year old, that is, during the first half of the first laying
year, than in older birds. Stated more specifically, in the flocks studied,
approximately one third to one half of the mortality among 5- to 12-
month-old birds and approximately three fourths of the mortality among
older birds were due to nonspecific disease.
The most frequently occurring abnormalities of the digestive organs
were enteritis (inflammation of the intestines), impaction of the crop
or gizzard, and degeneration (and, in many cases, rupture) of the liver.
The intestinal involvement produced many culls; liver degeneration
was usually fatal.
The principal changes involving the reproductive organs were rup-
tured yolk, with resultant peritonitis ; accumulations of all types of egg
material, including soft-shelled and fully formed eggs, in the abdominal
cavity ; and impaction of the oviduct with masses of solidified egg mate-
rial. Many of these cases were outwardly healthy and were culled because
Bul. 674] Diseases of Chickens 111
of unsatisfactory production. The accumulation of eggs and egg mate-
rial in the abdominal cavity was apparently a result of reverse peri-
stalsis, or backward movement of the oviduct, and the number of such
cases was surprisingly large.
The condition termed ruptured yolk, in the preceding paragraph, is
so prevalent in some flocks that it has been studied experimentally. It
is seen most frequently in pullets during periods of heavy egg produc-
tion. This suggested that it might be the result of feeding a laying ration
that was too stimulating, but this idea was not substantiated by experi-
mental results. In some studies that have been reported, the fowl-cholera
or the fowl-typhoid organism was isolated from about half of a large
number of cases that were examined, the others being bacteriologically
negative. Attempts to reproduce the condition, however, by injecting or
feeding laying chickens with bacteria isolated from the ruptured yolk
cases resulted in failure. In other investigations, no association between
ruptured yolk and bacterial infection was found. These results indicate
that the occurrence of ruptured yolk is not dependent upon bacterial in-
fection. Selective breeding studies recently reported indicate that rup-
tured yolk tends to be more prevalent in some families and consequently
that there may be a genetic basis for the occurrence of the trouble.
Death from ruptured yolk often occurs after a very brief illness and
may take place so suddenly that no evidence of sickness is observed.
Birds may be found dead on the roosts or in nests. The symptoms are
droopiness and discoloration of the comb. The constant finding en au-
topsy is yolk material in the abdominal cavity. This may look like a
normal yolk or be of a cheesy consistency. The membranes in the ab-
dominal cavity may be thickened. The abdominal organs, particularly
the liver, may be degenerated. Losses from ruptured yolk have sometimes
decreased when the diet has been changed so as to reduce egg production.
This has been accomplished by diluting the mash in use with an equal
quantity of bran or by giving two or three feedings daily of bran mois-
tened with hot water. When the latter procedure is used, access to other
feed should be prevented until the bran mash is eaten. Since fowl cholera
or fowl typhoid may also be present, specimens should be submitted to
a laboratory at once and the sanitary measures applicable to these dis-
eases carried out until the absence of these infections is demonstrated
by the bacteriological examination. Owners of breeding flocks which
suffer losses from ruptured yolks might obtain some relief by deter-
mining whether the trouble is most prevalent in certain families and
eliminating those worst affected.
In the birds which died from involvement of the urinary system, the
affected kidneys were pale and swollen and, in many cases, engorged
112 University of California — Experiment Station
with urates like those illustrated in figure 43. Some of the birds with
this condition died quickly and others lingered until they became ema-
ciated and were culled.
These nonspecific diseases constitute a serious cause of death and
culls among laying- chickens. Until some knowledge is obtained of the
causative factors and remedial measures, poultry raisers can be offered
no method of prevention of a considerable portion of the present high
mortality in their flocks. This emphasizes the importance of making full
use of the sanitary measures and more specific procedures for the pre-
vention of infectious and parasitic diseases.
CANNIBALISM
Losses from cannibalism in chicks and young laying chickens are of
real economic importance. In some flocks, it is the greatest single cause
of death. Whether it is a vicious habit or is related to a dietary deficiency
is a much discussed but still unsettled question.
In chicks and growing birds, it usually takes the form of toe, wing,
and tail picking. In many flocks of young laying birds and sometimes in
older ones, vent picking becomes prevalent. This is often referred to as
"prolapse of the oviduct" or simply "prolapse." A prolapse undoubtedly
does occur in many cases but would not be fatal if the victims were not
picked by the others. In many cases, however, the picking probably starts
at a slight injury or hemorrhage of the vent or even at the exposed, red-
dened mucous membrane after the passage of an egg. The picking in
many cases is continued until the victim is completely eviscerated. Vent
picking, or "pick-outs" as this is commonly called, is the most damaging
type of cannibalism. Feather pulling becomes prevalent in many flocks
of partly grown birds and layers. This, in itself, is damaging principally
in causing disfigurement of the birds, but the slight bleeding that may
follow pulling of the feathers often leads to fatal picking.
The tendency to toe, wing, and tail picking is greatest when chickens
are confined in crowded quarters and particularly if the floors are wire
mesh. Diets with a low protein level or deficient in salt (sodium chloride)
are also said to favor development of the vice.
Vent picking is less closely related to management or diet, but is likely
to be more prevalent among closely confined chickens.
There is considerable experimental evidence to indicate that feather
picking is influenced by the amount of fiber in the diet ; that is, the lower
the fiber content of the mash, the greater the tendency to feather picking.
The fiber can be supplied by ground oats, ground barley, or wheat bran.
The benefit of the fiber is said to be lost, however, if given in pellets
instead of in mash. The physical characteristics of the feed would seem
Bul. 674] Diseases of Chickens 113
of more significance, therefore, than its fiber content. This suggests fur-
ther that the cannibalistic tendency is less when chickens are forced to
spend a considerable portion of their time in eating. The time element
would be much greater with a mash and grain system of feeding than
when the food is supplied as pellets.
Some of the many measures that have been proposed for the preven-
tion of cannibalism are as follows :
Avoid raising chickens in large flocks, especially if they are confined
in the houses and on wire-mesh floors.
Darken the windows of brooder houses and illuminate with red electric
light globes or color the window glass red. This measure, while effective,
may necessitate closing the openings to the outside so tightly that it is
difficult to provide adequate ventilation.
Add from 0.5 to 2.0 per cent of salt, for 4 or 5 days, to the mash that
is being fed. This is said to stop cannibalism within 1 or 2 days. Another
"salt cure" that has been recommended consists of the addition of 1
tablespoon of salt to each gallon of drinking water for half of 2 successive
days at intervals of 3 days.
Watch the flock carefully so that picked chickens and also the more
aggressive pickers can be detected and removed before too much damage
is done. Keep the injured chicks segregated until the wound is healed
or smear the picked area liberally with pine tar or an antipick ointment
and return them to the flock.
An antipick ointment may be obtained readymade or may be prepared
by mixing together 4 ounces of vaseline, ^4 ounce of carmine, and V2
ounce of aloes.
Cut the upper beaks of all chickens back to the flesh of the roof of the
mouth. This is certain to be effective until the beaks grow out again.
Use deep litter and do not cover any more of the floor with wire mesh
than is necessary to satisfy sanitation requirements.
Feed mash that provides proper amounts of protein for the age of
the birds, and liberal amounts of ground oats or barley and wheat bran.
Attach one of the numerous types of antipick devices which are on
the market to the beak or over the vent of each chicken in a laying flock.
These are used extensively on poultry farms and are usually effective.
Some types are adaptable to chickens from 3 to 4 months old.
EXTERNAL PARASITES
GENERAL CHARACTERISTICS OF MITES
Two distinct groups of mites attack poultry. One group is periodic,
the parasite passing the greater portion of its life, not on the birds, but
in cracks and crevices about the poultry houses from which it makes
114 University of California — Experiment Station
nightly raids upon the roosting poultry to suck blood. The other group
passes the entire life cycle on the birds, burrowing beneath the scales of
the legs, into the skin at the bases of the feathers, into the shafts of the
feathers themselves, or even penetrating the internal air sacs. These
parasites may be distinguished from lice, by the facts that (1) an adult
mite has four pairs of legs, a louse three pairs (a larval mite has three
pairs of legs) and (2) the body of a mite is not divided into three distinct
regions, that is, head, thorax, and abdomen.
THE COMMON POULTRY MITE
The common poultry mite, Dermanyssus gallinae (fig. 49, A), is a
small mite. It is gray when unfed and reddish after having fed on blood,
which it draws from the birds by means of long, piercing, styletlike
mouth parts. When it is fully fed it is about the size of the head of a pin.
This mite customarily hides aw 7 ay in cracks and crevices about the hen
house during the day and migrates to the roosting birds at night to feed.
It may, however, remain for considerable periods of time on very weak
birds.
Symptoms and Diagnosis. — The common poultry mite is among the
most injurious of all species attacking poultry. It causes extreme irrita-
tion to the birds, which in heavy infestations become droopy, weak-
ened, progressively emaciated, and even die. The comb and wattles
become pale as a consequence of the anemia caused by loss of blood. The
irritation produced frequently causes laying hens to leave the nests.
Egg production is greatly decreased and resistance to other diseases may
be lowered. Infestations of this mite are especially serious in young
chicks.
The presence of this mite may be detected by tiny, circular black and
white dots ("pepper-and-salt marks") slightly smaller than flyspecks,
caused by its excrement, on the roosts and along cracks, as well as by
finding the mites themselves and their eggs in cracks and crevices, par-
ticularly those in the vicinity of the roosts.
Sources and Prevention of Infestation. — The common poultry mite
is probably introduced into clean flocks most commonly in contaminated
shipping coops. In some cases it may be brought in on introduced fowls,
since young mites feeding for the first time may remain continuously on
their hosts for as long as 3 days and 3 nights. In order to avoid the possi-
bility of thus introducing an infestation, newly acquired birds should be
quarantined in special coops for 3 days before being placed in the houses
or with other chickens. By the end of this time the mites will have left the
birds and be hiding in cracks in the coops. These coops should then be
thoroughly disinfected with one of the recommended sprays or with
Bul. 674]
Diseases of Chickens
115
boiling water, or be destroyed by burning. Shipping coops from other
poultry plants should not be left in or near clean houses, nor should
secondhand equipment be introduced unless the proper precautions of
disinfection are taken.
Infestations of this mite are sometimes acquired by the introduction
of poultry into old houses. This is readily understandable when one
recognizes that the mites may live for from 3 to 5 months without food.
Fig. 49. — A, The common poultry mite, Dcrmanyssus gallinae; B, mouth parts of
the tropical fowl mite, Liponyssus bursa. (From Ext. Cir. 8.)
Previously used vacant houses should be thoroughly cleaned, and sprayed
with a recommended spray, before birds are introduced into them. All
rubbish should be burned.
Wild birds, especially English sparrows, and rats and mice are ac-
ceptable substitute hosts and may introduce or maintain an infestation
of the common poultry mite. Therefore, poultry houses and runs should
be kept free of wild birds and rodents.
Control. — Cleanliness of the poultry houses and abundant sunlight
are of paramount importance in the control of the common poultry mite.
Since the mites are seldom found on the bodies of the birds during the
day, except in the first feeding period or in dark nest boxes, control
measures are directed most effectively against the hiding places such
as cracks and crevices, beneath boards and boxes, and under droppings
and other filth. As already indicated, a thorough cleanup of the premises
116 University of California — Experiment Station
to which the birds have access, together with the elimination of every
unnecessary article therein, such as boxes, coops, and boards, is the first
step to be taken. Old nesting material should be burned, and, if the in-
festation is severe, roosts and nests should be dismantled and replaced
if necessary by construction that will facilitate future cleanups. After
the building has been cleaned, it should be sprayed, with special atten-
tion to the roosts and cracks and crevices of the floors and walls. In
heavy infestations, the mites sometimes migrate to the outside of the
house when the inside is sprayed. They should be looked for along the
cracks on the outside and, if present there, a spraying of the outside is
indicated.
The spray may be applied by bucket or knapsack spray pumps or by
a power sprayer. A coarse spray is most effective and should be applied
to each area from several different angles to insure penetration into all
hiding places. There is considerable choice of sprays. The most satis-
factory of these are anthracene oil, paraffin oil emulsion (p. 21), or
crank-case oil to which from 10 to 15 per cent kerosene is added. The kill-
ing power of anthracene oil persists for several months, but sometimes it
is advisable to make a second application, or more, if necessary, about a
month later with a brush. Anthracene oil soaks into the wood rapidly
without leaving a greasy residue to soil the feet, feathers, and eggs of
the birds. The spraying of anthracene oil can be facilitated by adding
to it about an equal part of kerosene. Crank-case oil or crude oil diluted
with kerosene is efficient in killing the mites but does not possess the lon-
gevity of anthracene oil and leaves the roosts, floors, and walls in an oily
condition which readily soils the birds and persons working in the houses.
It should be remembered that the application of any highly inflammable
substance to a wooden structure greatly increases the fire hazard and
might present great difficulties in the collection of insurance in the event
of a subsequent fire. Regardless of the spray employed, the birds should
not be put back in until the houses have dried thoroughly.
Nicotine sulfate used on the roosts as described for louse control
(p. 126) is effective in killing mites feeding on the birds and in protecting
roosting birds. Used as a spray at the rate of 3 tablespoons per gallon
of water, to which is added % teaspoon of baking soda, it gives very sat-
isfactory results if applied carefully and in drenching quantities.
In those extreme cases where the control of the mite is impossible be-
cause of the character of the quarters, some relief may be afforded by
painting the roosts thoroughly with anthracene oil or crude oil and
wrapping the ends and other points of contact of the roosts with rags
soaked in the same substance, to prevent the mites from gaining access to
the fowls after they have roosted. To make this procedure effective, over-
Bul. 674] Diseases of Chickens 117
crowding should be avoided and the back and the ends of the roosts
should not be near enough to the wall to permit migration of the mites
to the plumage of the birds. Obviously, rags soaked with an inflammable
substance increase the fire hazard.
THE SCALY-LEG MITE
The scaly-leg mite, Anemidocoptes mutans (fig. 50), gets its name
from its habit of burrowing beneath the scales of the shank of the leg,
Fig. 50. — The scaly-leg mite, Anemidocoptes mutans, greatly
enlarged. (From Ext. Cir. 8.)
where its presence and activities cause a lifting of the scales and a
swollen condition of the shank. In extreme cases it produces such a pro-
nounced distortion and deformity that the affected birds are unable to
walk. Occasionally the comb and neck may be attacked. The mites usually
begin their attack between the toes. The general physical condition of
the birds is reduced in even moderate infestations. The scaly-leg mite is
microscopic, but a diagnosis can usually be made from the symptoms.
These symptoms are more commonly seen in the older birds.
118 University of California — Experiment Station
Sources of Infestation. — Birds become infested with scaly-leg mites
by the introduction of infested individuals into the flock or by being
placed on infested premises.
Control. — There are several satisfactory treatments for scaly-leg. The
legs may be dipped in crude petroleum or kerosene, preferably the
former, or washed with soap and warm water to soften the thickened
scales and crusts. Care should be taken to confine the oil to the affected
parts of the leg. Then the scales are carefully removed by rubbing with
the fingers. This must be done gently to avoid causing irritation and
bleeding of the underlying skin. After the crusts are removed, the legs
may be washed with some mild antiseptic and allowed to dry. After this
the legs are smeared with an ointment containing 15 per cent sulfur or 2
per cent carbolic acid, or with a mixture of 1 ounce of Peruvian balsam
and 3 ounces of ethyl (grain) alcohol. If carbolic acid ointment is used, it
must be handled and stored carefully because of its highly poisonous
nature.
A less thorough but also less laborious method of treatment is dipping
the legs of the birds in a mixture of equal parts of crude oil and raw
linseed oil, taking precaution to avoid wetting the legs above the scaly
portion. If marked improvement is not noted, the treatment should be
repeated in about 3 weeks ; this is, however, seldom necessary.
Bathing the infested legs three times at 2- to 4-week intervals with
a 0.5 per cent solution of sodium fluoride gives good results.
When the comb and neck are infested, they can be treated with the 15
per cent sulfur ointment previously mentioned.
Prevention. — In order to prevent spread of the infestation or reinfes-
tation, the poultry house and particularly the perches should be sprayed
under good pressure (150 to 300 pounds) with anthracene oil, crude
petroleum, or paraffin oil emulsion (p. 21).
The legs of newly acquired birds should be observed carefully in order
that infested birds may be segregated and treated before being placed
with the clean flock.
THE DEPLUMING MITE
The depluming mite, Cnemidocoptes laevis gallinae, is a microscopic
parasite which burrows into the skin at the bases of the feathers and pro-
duces an irritation which causes the birds to pluck out the feathers. This
leaves nude scaly areas at the more severely infested places. The condi-
tion is known as depluming mange, or scabies. The stumps of feathers
examined soon after the quill is broken will be observed to be surrounded
by scales or crusts, and adjoining feathers will be found to be similarly
affected. In this way depluming mange can be differentiated from the
feather-pulling vice discussed on page 112.
Bul. 674] Diseases of Chickens 119
Depluming mange usually begins in the spring and spreads rapidly
through the flock as the weather becomes warmer. The loss of feathers
ordinarily begins on the rump near the insertion of the tail feathers and
spreads to the back, neck, head, breast, and thighs ; only rarely are the
large tail and wing feathers lost. Egg production and weight gains may
be decreased. Male birds seem to be more susceptible than females.
Sources of Infestation. — Depluming-mite infestations are introduced
into a flock with the acquisition of newly infested birds or by placing
birds in houses or runs previously infested and not thoroughly cleaned
before the new birds are introduced. Spread is favored by any circum-
stances, such as copulation, which brings about bodily contact.
Control. — Depluming-mite infestations may be satisfactorily treated
by thoroughly soaking the birds in a dip composed of 10 pounds of finely
ground (350- to 500-mesh) wettable sulfur in 100 gallons of water on
the morning of a warm day when there is little wind. If the birds are
infested with lice, these parasites may be controlled at the same time by
the addition of % ounce of commercial sodium fluoride to each gallon
of dip. When only a few birds are involved, the affected parts may be
treated with an ointment made by thoroughly mixing 1 part of finely
ground sulfur with 4 parts of lard, vaseline, or lanolin.
Prevention. — Care should be exercised not to introduce infested birds
into a clean flock. Spread of the infestation can be prevented by treating
the birds as described above and at the same time cleaning the poultry
houses and spraying them as described in the discussion on the preven-
tion of scaly-leg. Infested cocks should not be used in breeding flocks
until they have been effectively treated because these birds may transmit
the infestation during treading.
THE TROPICAL FOWL MITE AND THE FEATHER MITE, OR
NORTHERN FOWL MITE
The tropical fowl mite, Liponyssus bursa (fig. 49, B, p. 115), and the
feather mite, or northern fowl mite, Liponyssus sylviarum, are very
closely related species which can be distinguished from one another only
by microscopic examination. They stay on the hosts or in the nest and
breed in both places, a habit which aids in differentiating them from the
common poultry mite (p. 114) , which customarily attacks the birds only
for short periods in order to feed and spends the rest of the time in
cracks about the roost, where it breeds. The entire life cycle of the tropi-
cal and the northern fowl mite from egg to adult requires only 8 to 12
days.
Symptoms and Diagnosis. — Since these mites hatch from eggs on
feathers attached to the birds or in the nest, and do not have to seek a
120 University of California — Experiment Station
host and since they grow to adults so fast, their multiplication is exceed-
ingly rapid, and infestations with them may quickly become very severe.
The mites are most numerous about the vent and tend to accumulate
on a few rather than many feathers, although in heavy infestations they
may be generally distributed over the body. These parasites give the
feathers a dirty appearance, and the skin in invaded areas becomes
scabby due to the irritation produced while they are sucking blood. An
untreated heavy infestation may result in death.
Sources of Infestation. — Infestations with these two species of mites
occur as the result of the introduction of infested birds into the flock,
placing birds in buildings in which an infestation already exists, or by
close contact with English sparrows or their nests.
Control. — The nicotine sulfate treatment described for the control of
lice (p. 126) will control these mites satisfactorily but should be applied
three times at intervals of 3 days instead of twice at intervals of 10 days
as recommended for lice. If necessary such a treatment should be repeated
still again after an interval of 2 weeks. A very satisfactory treatment
is to dip thoroughly each well-feathered bird in a solution made up of 1
gallon of water and 2 ounces of finely ground wettable sulfur. The dip-
ping should be done in the morning of a warm sunny day when little
wind is blowing or in a heated building, and the dip should be lukewarm
to reduce shock. The head should be submerged for an instant. In cold
weather fair results may be obtained by thoroughly dusting the adult
birds with wettable sulfur or pyrethrum. It does not seem advisable to
dust chicks with sulfur but pyrethrum may be used on them.
At the same time the birds are treated, regardless of the chemical
being used or its method of application, the building should be thor-
oughly cleaned, all nesting material and litter being removed and burned,
and the building sprayed completely with anthracene oil, paraffin-oil
emulsion (p. 21), or crude petroleum. The area over which the litter
is transported for burning and around which it is burned and the imple-
ments and vehicles used in transporting the litter should also be sprayed.
Since English sparrows harbor these parasites, their nests located in
and around poultry houses and runs should be destroyed by burning
and the area immediately around them should be sprayed.
Prevention. — Care should be taken not to introduce infested birds into
the flock and constant vigilance should be exercised to prevent English
sparrows from nesting in or adjacent to poultry houses. Clean birds
should not be placed in buildings until the buildings are known to be
free of these parasites. This may be done by placing a few birds in such
buildings and carefully examining them for mites a few hours later or
by making a minute examination of cracks and crevices.
Bul. 674] Diseases of Chickens 121
THE AIR-SAC MITE
The air-sac mite, Cytodites nudus, is a small oval mite which lives in
colonies in the respiratory organs and particularly in the air sacs, where
they can be seen as very minute yellow spots. They are able to penetrate
not only into the tracheae and bronchi, but also into all parts of the lungs,
the air sacs, and even into the air-containing cavities of the bones. Clini-
cal symptoms have rarely been observed even when the parasites were
very abundant. Some authors, however, have attributed clinical symp-
toms similar to tuberculosis or "going light" to heavy infestations of
these mites, and at least one case of obstruction of the bronchi with con-
sequent asphyxiation has been observed. The life cycle of this species is
unknown.
A definite diagnosis of air-sac-mite infestation can be made only at
autopsy.
No treatment is known for this infestation.
THE SUBCUTANEOUS MITE OF FOWL
The subcutaneous mite of fowl, Laminosioptes cysticola, has a long,
slender body and bears a line of division between its fused head and
thorax and its abdomen. This mite invades subcutaneous tissue, particu-
larly in those regions of the body where the skin is loose, such as the neck,
the breast, the flank, around the vent, and the thighs. There it causes
small, flat, oval nodules, which resemble bits of fat. When the mites die,
they become surrounded with caseous or calcified material. These mites
apparently do no harm to the host but may reduce the marketable value
of birds intended for human consumption. The life cycle of the mite and
its treatment and prevention are unknown.
THE QUILL MITE
The quill mite, Syringophilus hipectinatus, has been taken from poul-
try in California. This mite feeds on the quills, apparently chiefly or only
on those of feathers about to be dropped, and is generally believed to be
of no economic importance. In some instances, however, a peculiar molt,
involving over half the body, is produced. The mites are found in a
yellowish-gray or brownish powder in the quills but usually can be de-
tected only under a microscope.
DIFFERENTIATING TICKS FROM MITES
Ticks are closely related to mites, but they are always larger, easily
visible to the naked eye, and have a thick leathery cuticula, or skin. They
may be distinguished from mites also by the possession of a pair of
122
University of California — Experiment Station
breathing-pore plates situated on the side above, and usually behind, the
fourth pair of legs. Like mites, ticks have three pairs of legs in the larval
stage and four pairs in the adult.
THE FOWL TICK, OR BLUE BUG
The fowl tick, or blue bug, Argas persicus (fig. 51), is the only tick
attacking fowls that is of economic importance. The adult tick is flat,
egg-shaped in outline, dark brown in color, from % to 7 / 1Q inch in length,
and about half as wide at its widest part. The small, spherical, brown
Fig. 51. — Ventral and dorsal views of the fowl tick, or blue bug,
Argas persicus, enlarged. (From Ext. Cir. 8.)
eggs are laid in batches of from 20 to 100, in cracks and crevices of the
poultry house and under the bark of trees. A total of from 500 to 900
eggs are laid by each female. These eggs hatch in 3 weeks or more, and
the emerging larvae migrate, usually at night, to the birds and attach
themselves on those parts of the body where the feathers are not very
dense, especially under the wings, and gorge themselves with blood.
Complete engorgement requires about 5 days, rarely as long as 10 days.
After this the larvae drop off their hosts and hide away to transform to
the nymphal stage, which occurs after about 7 days. There are two
nymphal stages, each of which lasts about 2 weeks, in the life cycle of
this tick. It feeds but once for about 2 hours during each of these stages.
The nymphs, like the adults, attack their hosts only at night and hide
away in sheltered spots during the day. The adults feed approximately
once a month for a period of about 2 hours, and the females deposit a
batch of eggs after each meal.
Bul. 674] Diseases of Chickens 123
This tick is able to live for long periods without food. Adults and
nymphs are known to have survived nearly two and a half years of
starvation, and it is highly probable that in vacant infested poultry
houses some of them may successfully withstand fasting considerably
longer. The larvae, however, are not so resistant to the effects of starva-
tion, usually dying in about 3 months if they do not find a host. This
ability to exist for considerable periods of time without access to food
makes control of the parasite by starvation, through excluding all birds
from the houses, a very difficult matter, and explains the infestation of
clean birds which have been introduced in houses that have been vacant
for a year or more.
The fowl tick usually appears to be more abundant in the spring
months. This impression is created because the various stages of develop-
ment are greatly retarded during the winter months. In the spring the
ticks resume the normal developmental rate, which continues during
the hot, dry summer months.
Symptoms and Diagnosis. — Birds attacked by considerable numbers
of the fowl tick show a weakness of the limbs, extreme emaciation, and
paleness about the head. Egg production is greatly reduced or may en-
tirely cease. The growth of young birds is stunted. Sitting hens are very
seriously annoyed by the attacks of this parasite. In heavy infestations,
chickens lose vitality and may die from anemia, which is possibly supple-
mented by a poisonous secretion from the ticks. Young chicks are easily
killed by the effects of the ticks.
The fowl tick transmits fowl spirochaetosis, a fatal disease caused by
Treponema gallinarum, and poultry piroplasmosis, caused by Aegyp-
tianella pullorum, in those parts of the world where these diseases occur.
These diseases have not been reported from California.
Sources of Infestation. — Fowl-tick infestations are acquired by plac-
ing birds in infested buildings, by introducing infested birds into the
flock, and, less frequently, by contact with domestic or wild ducks, geese,
and turkeys.
Control. — Since the larval ticks remain on their hosts for a consider-
able time, sometimes as long as 10 days, it is highly advisable to treat
the birds as well as the buildings and runs. When flocks are small enough,
the birds should be placed in wooden crates, the cracks of which afford
ample hiding places for the ticks after they drop off the hosts, and kept
there for 10 days. In the meanwhile the buildings and runs should be
thoroughly cleaned of all rubbish and loose boards and the loose bark
of immediately adjacent trees removed. All of this debris is burned. If
the buildings are old and worthless, they are best burned. Buildings are
thoroughly sprayed with paraffin -oil emulsion (p. 21) or anthracene oil
124 University of California — Experiment Station
at a good pressure. The trunks and lower limbs of nearby trees should
also be sprayed. It is well, when the buildings have dried after spraying,
to eliminate hiding places as far as possible by closing all cracks with hot
tar. If the cleaning and spraying is not thoroughly done, the ticks may
not be exterminated, and then it is necessary to clean and spray the
building a second time after an interval of 10 days.
After the birds have been kept in crates for 10 days, they are removed
and returned to the clean buildings, and the crates are burned or dis-
infected with the spray used on the buildings or with scalding water.
If only a few fowls are infested with larval ticks, they may be dipped
in a 2 per cent solution of creolin ; the same procedure is followed as for
tropical fowl mite (p. 120) . This practice is also advisable in birds show-
ing signs of weakness resulting from an existing infestation of larval
ticks.
Prevention. — Birds should not be placed in buildings previously oc-
cupied by poultry, even though they may have been vacant for as long
as two and a half years or even longer, unless they are definitely known
to be free of ticks. This can be determined by placing a few white birds in
the buildings and examining them for ticks during the night. New birds
should not be introduced into the flock before they have been very thor-
oughly inspected for tick infestation or been quarantined in suitable
crates. If reinf estation is probable and no other prevention is feasible, a
considerable degree of protection may be afforded the birds by suspend-
ing the perches from the roof by wires which pass through small cups
of oil and arranging the roosts so that they have no contact with the
walls. This prevents the ticks from crawling onto the perches.
LICE
Lice can be distinguished from all other parasites on the body of
poultry by the facts that they have three pairs of legs in all stages and
their bodies are divided into three sections, the head, thorax, the abdo-
men, and flattened dorsoventrally, that is, as if a flattening force had
been applied on their backs. They seldom are over % c inch in length and
are of a yellow or grayish color, sometimes ornamented with dark stripes
(fig. 52) . They are never uniformly dark brown or red ; parasites of these
colors may be fleas, mites, or ticks.
The entire life of lice, including the egg stage, is spent on the body
of the birds. It is only by accident that the parasites leave their hosts
except to migrate to other hosts of the same species. The eggs require
about a week to hatch, after which maturity is reached in about 2 weeks.
It is not unusual to find at least six of the common species of lice on a
single bird.
Bul. 674]
Diseases of Chickens
125
The shaft louse, Menopon gallinae, and the body louse, E omenacanthus
stramineum, are perhaps the commonest poultry lice. They may be sep-
arated from all other chicken lice by the fact that their antennae are
buried in depressions and are not outstanding from the head. They are
both pale yellow in color, but the former has one row of bristles on the
back of each abdominal segment while the latter has two rows.
The wing louse, Lipeurus caponis, and the head louse, L. hetero-
graphus, have antennae that stand out, and the combined second and
third leg-bearing segments called the "pterothorax," from which the
last two pairs of legs originate, is square-sided. In the wing louse the
Fig.
-Three common species of poultry lice. (From Ext. Cir. 8.)
forehead, the area just in front of the antennae, is nearly straight-sided,
while in the head louse the sides of the forehead converge rapidly. The
posterior abdominal segments of the females vary in the amount of
heavily pigmented margins.
The fluff louse, the smallest of the common poultry lice (% inch) is
known as Goniocotes hologaster. The thorax is roughly triangular in
appearance. The antennae are outstanding and slender.
Symptoms and Diagnosis. — A few lice may cause no detectable dam-
age and produce no symptoms. Under suitable conditions, however, they
may multiply with amazing rapidity and therefore even a few lice are
potentially of considerable importance. They irritate the birds to such
an extent that they become very restless and neither feed nor sleep well.
Heavily infested hosts are in poor condition and show damaged plumage.
Lousiness results, in severe infestations, in marked decrease or cessation
of egg production, loss of weight or failure to gain properly, possible
loss of resistance to other diseases, and, with young chicks, even in
death. The head louse and the body louse ordinarily exert the most
serious influence upon the host of any of the species of lice. Diagnoses
126 University of California — Experiment Station
are very easily made by carefully inspecting the birds and detecting
the lice on the feathers or body.
Source of Infestation. — Louse infestations are acquired from contact
with infested birds. The parasites crawl from infested hosts to nonin-
f ested ones when they come in close contact with one another. Lice cannot
live long off a host.
Control. — A highly effective and easily applied method of treating
chickens for all species of lice except the head louse consists of applying
Black Leaf 40 to the roosts in a thin layer (about % pound per 100 feet
of roosts) just before roosting time. The back and ends of the house
should be closed but the front should be partially open to avoid the pos-
sibility of injury to the birds from the fumes. The flock should be in-
spected during the first 2 evenings after treatment, and all birds placed
on the roost that are found roosting elsewhere. The warmth of the birds'
bodies causes the chemical to evaporate, permeate the feathers, and kill
the lice by fumigation. Perfect control from a single treatment has been
obtained in many instances even when the temperature during the night
has approached freezing. Failures that have occurred are probably at-
tributable to windy or drafty locations of the roosts or an unfavorable
atmospheric condition of an, as yet, unknown character. Since unharmed
louse eggs have been found on treated birds, a repetition of the treatment
in 10 days is advisable. In lieu of this, the birds should be closely ob-
served for at least 2 weeks and treated again if any young lice appear.
Tests with a solution of pure nicotine sulfate conforming to Black Leaf
40 in hydrogen-ion concentration and content of nicotine sulfate have
invariably failed to destroy the lice. This would indicate that the effec-
tiveness of Black Leaf 40 is not due solely to the nicotine sulfate it con-
tains. Under no circumstances should the treatment be applied when
roosts are freshly whitewashed nor should a preparation of pure nicotine
(nicotine alkaloid) be substituted.
Sodium fluoride (commercial grade) is a highly effective chemical for
the individual treatment of chickens for lice. It is a stomach poison for
lice and remains on the bodies of the birds long enough to kill the young
lice that hatch from eggs which were on the feathers when the birds were
treated. There are three methods of application, the pinch method,
dusting, and dipping. The pinch method consists in rubbing pinches of
sodium fluoride on the skin, not merely on the feathers, as follows : one
on the head, one on the neck, two on the back, one on the breast, one
below the vent, one on the tail, one on each thigh, and one on the under-
side of each wing. This is the best method to use for head lice on old and
weak or young birds. The chemical should be applied cautiously and in
very small pinches to young birds.
Bul. 674] Diseases of Chickens 127
In the dusting method, the sodium fluoride is diluted with 3 parts of
flour or talc. Then the bird is inverted and the dust is applied liberally
with a shaker while thoroughly ruffling the feathers.
Dipping is the most economical and rapid method of applying sodium
fluoride and is most suitable for large flocks. The dip does not irritate
the respiratory tract of the operator as does the powder in the pinch or
dusting method. To make the dip, 1 ounce of commercial sodium fluoride
is dissolved in 1 gallon of warm water. Dipping should be done only on
the morning of a warm day. The bird should be inserted into the dip feet
first, the feathers should be ruffled to permit the dip to penetrate to the
skin, and the head should be ducked once or twice before taking the bird
out.
One pound of sodium fluoride will treat 100 birds by the pinch method
and 200 by dipping.
Sodium fluosilicate, finely ground sulfur, or a dusting powder made
of 3 parts benzine and 1 part carbolic acid, to which is added sufficient
plaster of paris to absorb the liquid, applied in the same way as described
for sodium fluoride dusting, gives good results. It must be remembered,
however, that carbolic acid is very poisonous.
Mercurial, or blue, ointment, if rubbed on the skin just below the
vent, a quantity about the size of a pea being used, will kill body lice
going to the vent for moisture. Mercurial ointment, however, is very
poisonous and consequently must be handled with care.
Head lice on young chicks can be effectively controlled by the applica-
tion of cottonseed or any other bland oil or soft fat to the infested region.
Prevention. — Louse infestations may be prevented by carefully in-
specting all new birds before they are introduced into the flock and
quarantining and treating if necessary, and by otherwise avoiding con-
tact with infested birds. Excessive infestation may be prevented to some
extent by supplying the birds with ample dusting boxes filled with fine
road dust to which sodium fluosilicate has been added at the rate of 1 part
of the chemical to 3 parts of dust. This latter procedure should be re-
garded merely as an adjunct to the more effective practices described
above and should not be relied upon too heavily. Spraying the house and
roosts has no effect on louse infestations. Brooding hens, unless definitely
known to be free of lice, should be treated before being placed with
newly hatched chicks.
GENERAL CHARACTERISTICS OF FLEAS
Fleas may be distinguished by their dark brown color, the presence of
three pairs of long legs adapted for jumping, the absence of wings, and
the laterally flattened body. Three species of fleas are known to attack
128 University of California — Experiment Station
poultry ; but one of these, the European hen flea, Ceratophyllus gallinae,
has not been reported from western North America and hence will not
be discussed in this bulletin.
THE STICKTIGHT FLEA
Although the sticktight flea, Echidnophaga gallinacea, is parasitic on
dogs, cats, rats, and other wild mammals, as well as several species of
wild birds, it habitually attacks poultry and finds this host admirably
suited for its purposes. The sticktight flea, unlike most other species of
fleas, remains tightly attached in clusters to the host throughout adult
life. The eggs laid by the attached females ordinarily fall to the ground
and hatch. In rare instances the eggs are retained in the burrows or
ulcers caused by the imbedded females. In such cases the larvae upon
hatching usually fall to the ground, but they may remain in the tissues,
where they produce a condition resembling the invasion of tissues by
blowfly maggots. These larvae are tiny, white, caterpillarlike organisms
with chewing mouth parts. They subsist on blood which is constantly
being evacuated by the adult fleas and falls with the eggs to the ground.
When the larvae become full grown, they spin a whitish cocoon, within
which they change from the larval stage to that of an adult, after which
they attach themselves to the skin of their host and suck blood.
Symptoms and Diagnosis. — On chickens the sticktight flea is confined
to the face, ear lobes, wattles, and comb and is most frequently attached
about the eyelids and comb. The constant irritation, particularly in spots
where the fleas are closely aggregated and present in large numbers, to-
gether with the slight burrowing activity of the insects, causes the forma-
tion of ulcers so extensive at times that blindness and subsequent death
are produced. Young fowls when heavily infested often die quickly. Even
mild infestations reduce egg production and retard growth. Diagnosis is
made by finding adult fleas on the hosts or larvae in the litter.
Sources of Infestation. — Sticktight-flea infestations are acquired by
contact, direct or indirect, with infested poultry, wild birds such as
quail, Brewer's blackbirds, and English sparrows, rats, mice, dogs, and
cats, and by the introduction of chickens into infested buildings. Under
dry and cool conditions, these fleas may remain alive for some months
in vacant poultry buildings and runs and may be maintained in consider-
able numbers in such places by hosts other than poultry.
Control. — The first step in the control of this parasite is thorough
cleaning of the infested buildings and pens and the burning of all rub-
bish collected. This is followed by a thorough spraying with paraffin-oil
emulsion (p. 21), crude oil, kerosene, kerosene emulsion (p. 21), or a
reliable proprietary pyrethrum spray fortified with lauryl thiocyanate.
Bul. 674] Diseases of Chickens 129
These fleas cannot thrive in damp places and if the yards are sprinkled
two or three times a week, for a week or two, breeding is greatly reduced.
One of the most efficient methods of preventing breeding is to scatter
salt freely about the yards and then wet the soil thoroughly. Fowls must
not be permitted to eat the salt because it is poisonous to them.
The sticktight flea can be killed on the birds by the application of 2
per cent carbolic ointment, mercuric ointment, sulfur mixed with 5
parts of a bland oil, an ointment made up of 1 part kerosene and 2 parts
lard, or tincture of iodine. Great care must be exercised, however, not
to get any of the ointments in the birds' eyes, for they may produce
blindness. The application of these ointments must be confined to the
seats of infestation.
All manure and other scrapings from the poultry houses and yards
that are to be used for fertilizing purposes should be turned under. The
mere storing of the manure outside of the house in piles or spreading it
on fields will not prevent the development of the flea larvae to the adult
stage, although it will prevent them from gaining direct access to con-
fined fowls; the cats, dogs, and men of the neighborhood will be the
alternative recipients of their attention unless the manure is carefully
turned under by plowing or spading.
Prevention. — The exclusion of wild birds, dogs, and cats from poultry
houses and runs and. rigid rat and mouse control are very essential in
the prevention of sticktight-flea infestations. New birds should not be
introduced into the flock until it has been definitely ascertained that
they are free of this parasite and care should be taken to determine that
buildings into which poultry are to be placed are free of fleas.
THE WESTERN HEN FLEA
The western hen flea, Ceratophyllus niger, may at times be a serious
pest of poultry. This flea is considerably larger than the sticktight flea
and attaches itself to its host only for short periods of time to suck blood,
usually leaving the host's body between meals and spending its time in
the litter of the nests, although it may occasionally remain unattached
on the host. It is a voracious feeder and attacks men more readily than
does the sticktight flea. The habits are otherwise like those of the stick-
tight flea.
Symptoms and Diagnosis. — Birds infested with the western hen flea
show a decrease in egg production. In heavily infested flocks, laying may
cease entirely and the birds become emaciated. In especially severe cases,
death may result. Young birds appear to be more severely affected than
older ones.
A diagnosis is most readily made by finding the fleas in the litter.
130 University of California — Experiment Station
Control. — The control methods are the same as those described for
sticktight-flea infestations with the exception that ointments are never
applied since the parasites are not permanently attached and do not
appear in clusters on the host.
Prevention. — The preventive practices are the same as those described
for the sticktight flea.
THE COMMON HOUSE FLY
The common house fly, Musca domestica, lays its eggs preferably on
freshly deposited manure, but it will also utilize for this purpose decom-
posing vegetable and animal matter or even moist soil saturated with
nitrogenous material. When garbage is fed, unless extra precautions are
taken, particularly heavy fly breeding will occur because of the attrac-
tiveness of this material to flies. These eggs hatch in about 2 days into
tiny, glistening white, footless maggots that grow rapidly for approxi-
mately a week until about % inch in length, when they migrate from
the moister part of the medium in which they are developing to a drier
portion or to surrounding soil ; here they transform into brown, barrel-
shaped pupae, from which they emerge as full-grown flies in about
4 days.
House-fly control around poultry plants is important not only because
of the annoyance these insects cause man and of the possibility of carry-
ing filth and disease-producing organisms to his fowls but also because
they serve as intermediate hosts for some of the poultry tapeworms.
Control. — Removal of droppings and moist litter from the poultry
houses and yards at intervals of less than 7 days is essential in controlling
house flies on poultry ranches.
Where poultry manure has a definite cash value, the droppings (scrap-
ings from the droppings board) and the sweepings (material from floors
and yards) are segregated in fly-tight bins and collected at frequent
intervals.
Many producers accomplish the same results during the dry season by
spreading the manure daily on plots to be fertilized, in a thin layer that
will dry out rapidly. The fly larvae will be destroyed by the drying, but
the manure should be plowed under about once a week where flea infes-
tations exist, to avoid the emergence of these latter insects.
The maggot trap is another effective method of fly control where
poultry manure is concerned. This consists of a concrete pan about 9 feet
long, 12 feet wide, 6 inches deep, and with walls 4 inches thick. This is
kept filled with water to which a film of oil is added. A table with legs
IV2 f ee t high and slightly smaller in area than that of the pan is placed
in the pan. The top of the table is made of crossed inch laths spaced
Bul. 674] Diseases of Chickens 131
their own width apart, leaving a latticed appearance, and covered with
straw to prevent the manure from falling through. The manure is then
placed on this table or rack and moistened enough to make it thoroughly
wet but not dripping. Each addition of excreta is treated in the same
way, the whole deposit kept wet at all times. The fly larvae flourish under
this treatment, but when ready to pupate their search for a dry place
ends invariably in a fall to the oil-filmed water in the pan below. If
the manure is collected regularly and placed on the maggot trap and
if the mass of manure is kept wet, this method will return 100 per cent
efficiency.
Dead fowls should be disposed of promptly through the garbage-col-
lection system in cities and towns or by incineration in rural areas. If
it is necessary to bury dead birds, or other dead animals, a hole at least
1% feet deep should be prepared, the body covered with a crude oil,
and the ground well tamped.
Adequate, flyproof storage receptacles for kitchen refuse are essential
in the prevention of fly breeding. The addition of a small quantity of
turpentine to vessels containing garbage acts as a repellent and is harm-
less. Where there is no effective garbage-collection service, the garbage
should not be permitted to accumulate beyond reasonable limits.
Septic tanks should be kept in a condition of good repair and kept
tightly sealed in order that flies may not have access to their contents
and breed in them.
Particular care should be taken to the feeding of wet mash and liquid
milk in order to prevent their accumulating and becoming a source of
fly breeding.
Creosote oil sprayed on fences, walls, and floors will repel adult flies,
but the penetrating odor is disagreeable, although it is less messy than
crude oil or fuel oil and does not present the fire hazard of the latter
materials.
If the manure cannot be disposed of promptly and adequately, poisons
may be applied to kill the fly larvae, but most of these materials interfere
to a greater or lesser degree with the fertilizing value.
Powdered hellebore (powdered roots of Veratrum album or V. viride)
is employed in the chemical treatment of manure to prevent fly breeding.
One-half pound of powdered hellebore is stirred in 10 gallons of water
and allowed to stand for 24 hours before using. This solution is spread
over the manure at the rate of 10 gallons to each 10 cubic feet of refuse
material. The hellebore solution is somewhat poisonous and livestock
should be prevented from drinking it. Poultry, however, are not poisoned
by pecking at hellebore-treated material ; but still it is not desirable, for
other and obvious reasons, for them to have free access to manure piles.
132 University of California — Experiment Station
No injury to plants appears to result from fertilization with hellebore-
treated manure.
Powdered borax, which has the advantages of being inexpensive, com-
paratively nonpoisonous, and noninflammable, is effective in preventing
fly breeding in manure piles. Three-quarters of a pound of powdered
borax is dissolved in 10 gallons of water and sprinkled over the manure
at the same rate as given above for the powdered hellebore treatment. It
is inadvisable, however, to utilize borax-treated manure as fertilizer
repeatedly on soils because this may create too high a boron content.
Creosote oil may be sprayed on each daily addition to the manure pile
at the rate of 1 gallon to the ton of excreta if it is not to be used as
fertilizer.
Electric fly traps have come into widespread use and are probably
more efficient than any other device for catching flies, but it should be
recognized that even though large numbers of adult flies may be cap-
tured, this is only a palliative measure, and that no real relief from these
pests can be obtained unless the control measures are directed against
the breeding places. Only electric traps approved by the Underwriter's
Laboratory should be employed, in order to avoid accidental burns or
electrocutions and fires.
Poisoned fly baits are sometimes used, but these, like the electric traps,
are only palliative since they do not control the breeding places. Perhaps
the most commonly used of these is formalin, which is poisonous to
higher animals and man as well as to flies. A pint of a 1% to 2 per cent
solution, is added to 1 pint of diluted canned milk, 1 pound of sugar,
and 3 gallons of water. A small piece of bread or sponge is placed in a
shallow dish and saturated with the formalinized bait. The bait must
be replenished regularly and frequently.
Another effective poison bait, which is used in the same way as the
formalin solution, is composed of 3 tablespoons of sodium salicylate
dissolved in 1 pint of water.
WOUND-INVADING MAGGOTS
A number of species of flies, the most important of which are the
blowflies (Lucilia species), the wool maggot (Phormia regina), the pri-
mary screwworm (Cochliomyia americana), and the secondary screw-
worm (0. macellaria) , produce larvae which invade wounds, both large
and small, and thereby cause serious damage. The blowflies and the wool
maggots will deposit their eggs on or adjacent to either fresh or old
wounds. The primary screwworm has a very strong preference for fresh
wounds. The secondary screwworm prefers older wounds in which some
necrosis has occurred.
Bul. 674] Diseases of Chickens 133
Symptoms and Diagnosis. — The larvae hatching from the eggs de-
posited on or adjacent to wounds burrow into and feed upon the tissues
of the host. They very quickly create extensive damage and frequently
produce death unless effective treatment is promptly initiated. Maggots
hatching in feces which have collected on the feathers around the vent
may invade the cloaca, penetrate into the abdominal cavity, and cause
a fatal peritonitis. Diagnosis is made by the examination of wounds,
which when infested typically have a bloody exudate, and detection of
the maggots, which may be so deeply imbedded in the tissues that only
the flat posterior tip of their bodies are visible.
Treatment. — Maggot-infested wounds should be cleaned by gentle
swabbing with absorbent cotton and then irrigated with commercial
benzol or a mixture of 15 parts chloroform and 85 parts bland oil (olive
oil, cottonseed oil, or liquid petroleum). When benzol is used, a small
amount is sprayed on the wound to stop the flow of blood and serum ;
then more benzol is added and the wound is plugged with cotton. The
plug is kept in place for at least 3 minutes to allow the fumes to penetrate
and kill the maggots. The chloroform-oil solution will ordinarily cause
most of the maggots to leave the recesses of the wound before they
die ; the benzol will do this to a lesser degree. As many dead larvae re-
maining in the wound should be removed with blunt-pointed forceps
as is possible without causing bleeding. The wound is then covered with
diphenylamine.
Smear no. 62, which contains 35 per cent benzol, 35 per cent dipheny-
lamine, 10 per cent turkey-red oil, and 20 per cent lampblack, will kill
older maggots in the wound as well as prevent younger ones from de-
veloping; but when this material is employed the dead maggots are left
in the wound, unless they migrate to the surface before dying.
Cloacal infestations are best treated by irrigation with small quan-
tities of carbon tetrachloride.
Prevention. — In order to prevent maggot invasion, the flock should
be watched for birds with wounds or collections of feces on the feathers
beneath the vent. Injured birds should be kept out of the flock until the
wounds are healed. Manure should be removed from the feathers around
the vent and the birds in which such contamination occurs should be
kept out of the flock until it is discovered that no more fecal material
will collect.
Noninfested wounds should be coated with Smear no. 62 or covered
with diphenylamine, which must be ground sufficiently fine so that at
least 50 per cent will pass through a screen having 40 meshes to the inch.
Diphenylamine has a tendency to cake, especially when the containers
are exposed for a time to high temperatures. When this occurs, regrind-
134 University of California — Experiment Station
ing to its original fineness is necessary before the material can be used.
Storage in a cool place in tight metal or wooden containers will aid in
preventing excessive caking of the chemical.
Sharp objects, such as splintered ends of boards or ends of wire in
houses, on which chickens can be readily injured should be avoided. Care
should be taken not to frighten the chickens by sudden entrance, espe-
cially of strangers, into houses or when catching them, for this may
cause them to fly against side walls, wire-mesh fronts, or pieces of
equipment.
Wound-invading flies should be controlled by the disposal of dead
birds. All dead bodies, whether or not they are infested with maggots,
must be promptly disposed of by burning or thoroughly poisoning with
arsenic and burying at a depth of at least 2V£ f eet .
THE COMMON BEDBUG AND THE MEXICAN CHICKEN BUG
The true bugs which attack poultry may be distinguished from other
insects by the flattened body, elongate oval shape, yellowish-brown to
dark-brown color, long 4- jointed antennae, and vestigial wings. The
compound eyes protrude conspicuously from the sides of the head and
the first thoracic segment is large and deeply notched anteriorly where
the head is inserted. The abdomen has eight visible segments, and the
entire body is covered with bristles and hairs. On the ventral side of
the thorax are stink glands, which impart a characteristic odor to these
insects.
In California only two species of this group, the common bedbug
(Cimex lectularius) and the Mexican chicken bug {Haemato siphon in-
odorus), are known to attack poultry. These bugs hide away in cracks
and crevices near the sleeping places of their hosts and usually suck
blood only at night. They will, however, bite setting hens in the daytime.
They can successfully withstand starvation for at least several months.
Under favorable conditions they are able to multiply very rapidly.
Symptoms and Diagnosis. — These insects at times cause severe irrita-
tion and anemia in poultry. Their presence may be detected by the care-
ful examination of cracks and crevices, particularly those near the roosts
and nesting boxes.
Sources of Infestation. — The bugs gain access to poultry houses from
adjacent infested human habitations and from visiting wild birds.
Control. — Poultry houses should be thoroughly cleaned and all rub-
bish removed and burned. The cracks and crevices should be thoroughly
sprayed with paraffin-oil emulsion (p. 21), or a good commercial py-
rethrum spray fortified with lauryl thiocyanate. Also, it is well to close
all such hiding places by painting them with hot tar.
Bul. 674] Diseases of Chickens 135
Prevention. — All buildings should be determined to be free of these
parasites before birds are placed in them. Second-hand equipment should
be carefully inspected, and treated if necessary, before being placed in
clean houses. Infested human habitations on poultry farms should be
ridded of bedbugs.
INTERNAL PARASITES
FLUKES
Flukes are unsegmented worms which are flattened and leaflike in
most cases. They generally possess one or two cup-shaped suckers, which
are organs of attachment ; when two suckers are present, one is anterior
and the other is ventral or posterior. All of the species known to normally
parasitize poultry are hermaphroditic. Their eggs, which are eliminated
from the body of the fowl with the feces, hatch in the presence of mois-
ture. The larval forms that emerge seek an intermediate host, an appro-
priate species of snail, in which they grow and then divide into a varying
number of daughter larvae. These latter forms migrate from the body of
the snail and, in the case of the poultry flukes here considered, penetrate
the bodies of second intermediate hosts, such as tadpoles and dragonfly
nymphs, where they await until these hosts are eaten by the birds.
Echinoparyphium recurvatum, the only fluke that has been reported
from poultry in California, is a small leechlike intestinal fluke, %
inch long, which attaches itself to the lining of the small intestine. It is
characterized by a collar of heavy spines about the sucker at the anterior
end of the body. The eggs of this parasite escape from the body of the
host in the feces and hatch, when they come in contact with water, into
swimming embryos which migrate through the water to appropriate
snails, in whose bodies a multiplication occurs. The still immature, but
more advanced, forms escape from the intermediate host and migrate
to tadpoles, in the kidneys of which they encyst. Fowls acquire the flukes,
still in an immature stage, by eating infected tadpoles.
Symptoms and Diagnosis. — Fowls infected with Echinoparyphium
recurvatum become emaciated, anemic, and sometimes show weakness
of the legs. Post-mortem examinations reveal a marked inflammation
and swelling of the intestinal lining. In heavy infections there is fre-
quently a fatal termination. Diagnosis is made by finding the worms in
the intestine at autopsy or by detecting the presence of the eggs in the
droppings by microscopic examination.
Treatment. — Carbon tetrachloride or tetrachlorethylene is adminis-
tered in doses of from 1 to 2 cc, according to the weight of the bird.
The drug is best administered with about 3 cc of paraffin oil by means
of a syringe and a piece of narrow, flexible rubber tubing about 10 cm
136 University of California — Experiment Station
long which is gently pushed down the esophagus into the crop. It may
also be given in gelatin capsules, but great care must be taken that
these capsules are not broken in the mouth during administration.
Chickens in fair condition will tolerate a dosage as high as 4 cc for
each 2.2 pounds of body weight, but doses of this size will result fre-
quently in transient diarrhea and, in the case of laying birds, decrease
in egg production for a few days. Such dosage, however, is likely to be
toxic for emaciated or very weak chickens.
Prevention. — Poultry should not have access to streams, ditches, or
ponds where they can procure tadpoles. Medication should be considered
as a preventive as well as a therapeutic measure since, if thoroughly
conducted, it prevents the further spread of the infection.
TAPEWORMS
The effects of tapeworm infections in poultry are so insidious that their
presence is often entirely overlooked. These worms, inhabitants of the
intestines, when full-grown, range from almost microscopic size to 10
inches in length, according to the species. They have a scolex, or "head,"
by which they attach themselves to the intestinal walls. Attached to the
scolex, by a "neck" in most cases, is a series, variable in number, of
flattened "segments," or proglottides. They absorb their food directly
through the body wall. The posterior segments break off and appear in
the feces as glistening white pearly objects which, in freshly voided
droppings, can move about slowly by expanding and contracting. These
segments contain eggs which are harmless to chickens but when eaten
by some other animal which can serve as an intermediate host (see
table 1) develop into larval tapeworms. These larval forms remain in
the intermediate host until it is eaten by a chicken. Then the larvae
attach themselves to the lining of the intestines of the chicken and
develop into mature worms (fig. 53) .
Amoebotaenia sphenoides is a very small tapeworm. It has from 15
to 30 narrow segments and is found throughout the duodenum. It is
relatively uncommon and is seldom of economic importance. Its inter-
mediate host is the earthworm. Although this tapeworm is practically
harmless in otherwise normal and healthy poultry, it may aggravate
the symptoms produced by other factors which affect the health of the
birds.
Choanotaeniainfundibulum (fig. 54, B) is the most common tapeworm
in California. Its specific name relates to the shape of the mature seg-
ments, which are funnel-shaped, the posterior ends being wide and in-
vaginated for the reception of the following segment. The larvae of
house flies (Musca domestica) and the dung beetle (Geotrupes sylva-
Bul. 674]
Diseases of Chickens
137
ticus) serve as intermediate hosts. In house flies, the infection continues
through the larval and pupal stages and persists in the adult. Choano-
taenia infundibulum is not, under normal conditions, a particularly
serious tapeworm. The symptoms it produces are similar to those caused
by Davainea proglottina but are much less severe. This parasite, like the
other larger tapeworms, may in heavy infections practically occlude the
intestine with the consequent serious disturbance of the normal move-
ment of the intestinal contents.
TABLE 1
Poultry Tapeworms in the United States
Tapeworm
Primary hosts
other than chickens
Length '
when mature
segments are
formed
Intermediate host
Amoebotaenia spkenoides (rare) . .
Choanotaenia infundibulum
(uncommon)
Davainea proglottina
Hymenolepis cantaniana (rare). .
None
Turkey, Hungarian partridge. .
Turkey
Turkey, peacock, pheasant . .
inches
y*-x
M- 10
Vxi-y?
1-3
Vs-5
2-10
K-io
Earthworms
House fly, dung beetle
Slugs
?
Raillietina cesticillus (common) .
R. echinobothrida (cause of
Pheasant, turkey, guinea fowl
Turkey, pigeon
Turkey, guinea fowl, quail. . . .
Ground beetle, dung
beetle
■ slugs (?)
Davainea proglottina is one of the smaller tapeworms of poultry, being
less than % inch long and consisting of only 4 or 5 segments, and is con-
sidered by some authorities to be the most harmful of the poultry tape-
worms. It is found exclusively in the second half of the fore part of the
small intestine, deeply imbedded in the mucosa. Its intermediate hosts
are slugs. Young birds are more susceptible to this parasite than are
older ones. Infected birds lose their appetites, become droopy, are usually
thirsty and show anemia and emaciation. Egg production decreases or
is even entirely suspended. Diarrhea may occur and the feces may be
discolored with blood. Often there are signs of extreme weakness, espe-
cially in the legs. Light infections merely result in unthriftiness of the
birds, but heavy infections may be fatal.
Hymenolepis carioca, commonly known as the "thread tapeworm of
poultry/' is about 3 inches long when fully grown, but is threadlike
in thickness. Its scolex (fig. 54, A) is particularly difficult to obtain
at autopsies because the worm breaks readily, and this portion is lost.
The intermediate hosts are dung beetles and stable flies (Stomoxys
calcitrans) . This parasite produces symptoms similar to those produced
138
University of California — Experiment Station
by Raillietina cesticillus and in heavy infections may cause marked
symptoms.
Raillietina cesticillus is the most common member of this genus in
California. Its scolex (fig. 54, E) is flat and inconspicuous and domi-
nated by a protuberance covered with tiny hooks. The suckers are in-
conspicuous and without spines. The mature worm is from % to 5 inches
long. The young worms are usually attached to the posterior portion of
the fore part of the small intestine, but the older worms are more apt
to be found in the anterior part of the small intestine. Dung beetles and
Fig. 53. — Inside of a hen's intestine, showing attached tapeworms, two times
natural size. At post-mortem examination, the worms appear much longer and
more transparent, but they contract and become whiter at death. (From Ext.
Cir. 8.)
ground beetles act as intermediate hosts of this tapeworm. The symptoms
are like those produced by R. tetragona but usually somewhat less severe.
Raillietina echinobothrida (fig. 54, D ) , sometimes known as the "spiny-
suckered tapeworm," is one of the most serious tapeworms of poultry.
This is one of the larger species of tapeworms found in chickens; it at-
tains a length up to 10 inches and is found in the lower portion of the
small intestine. It utilizes ants, land snails, and possibly slugs as inter-
mediate hosts. Infections with this tapeworm give rise to nodules vary-
ing from the size of a pinpoint to that of a pea, on the outside of the
intestines ; this condition is known as "nodular taeniasis." Nodules are
often bunched, several coalescing to form what appears to be a single
large one. When numerous, they interfere with the nutrition of the bird,
and progressive emaciation results. This tapeworm ranks next in serious-
ness to Davainea proglottina.
Bul. 674]
Diseases of Chickens
139
The nodules produced by this tapeworm so closely resemble those
caused by tuberculosis (p. 76) that the former can be distinguished only
if the parasites are found protruding from a nodule into the interior of
the intestines. Unfortunately, however, after causing a nodule, the worm
may change its position, so that at autopsy none will be found attached
Fig. 54. — Scolices, or "heads," of the common poultry tapeworms greatly en-
larged but drawn to the same scale: A, Hymenolepis carioca; B, Choanotaenia
infundibulum ; C, Baillietina tetragona; D, B. echinobothrida ; E, B. cesticillus;
F, Metroliasthes lucida. (From Ext. Cir. 8.)
to a nodule. Therefore, when nodules on the intestines are found at
autopsy of a chicken on the farm, specimens should be submitted to a
laboratory (see footnote 14, p. 24) where a definite diagnosis can be
obtained.
Raillietina tetragona (fig. 54, C) is closely related to the preceding
species and, like it, has thorny suckers; it is about the same size and in-
habits the same portion of the intestine. It utilizes house flies and ants
as intermediate hosts. This parasite produces in poultry symptoms simi-
140 University of California — Experiment Station
lar to those described for Davainea proglottina (p. 137) and is nearly as
serious ; it does not produce nodules.
Diagnosis. — At post-mortem examination the lining of the small in-
testine is seen to be thickened and may be bleeding. The presence of the
parasite is easily overlooked because it is partially embedded in the
tissue and is frequently too small to be readily recognized. If scrapings
from the infected intestinal lining are placed in water in a flat dish,
however, the worms can be detected easily. Diagnosis can also be made
by finding the eggs in the droppings, under microscopic examination;
especially in droppings samples passed in the early afternoon.
Prevention. — In order to prevent infections with tapeworms, chick-
ens must be kept from eating the intermediate hosts (see table 1 ) , prefer-
ably by exterminating the latter.
When slugs are involved as intermediate hosts, they may be controlled
in a given area by the use of a poison bait. One-quarter ounce of metalde-
hyde ground up and thoroughly mixed with 8 ounces of bran makes a
satisfactory bait. After the metaldehyde and bran are mixed, sufficient
water is added to make the bait moist. The bait is put out toward eve-
ning in small piles of approximately 1 teaspoon each ; one pile to about
each 2 square feet of soil surface. Care must be taken in dry areas to keep
the baits moist. The metaldehyde baits which also contain calcium arse-
nate are more efficient than those without the arsenical. A very satisfac-
tory bait formula is the following : 2 tablespoons blackstrap molasses, 1
ounce calcium arsenate, % ounce metaldehyde, 1 pound bran, 1 pint
water. In making this latter bait, the calcium arsenate and metaldehyde
are first thoroughly mixed with the bran and then the molasses, dis-
solved in the water, is added. Chickens possess a marked tolerance to
arsenicals and are not poisoned by metaldehyde, but despite this, baits
placed in chicken yards or other places to which chickens have access
should be picked up each morning before the birds can feed upon them.
There is no known- practical method of chemical control of earth-
worms, but their abundance may be reduced to a negligible quantity
by keeping the runs dry and well drained, avoiding the spilling and
accumulation of water from drinking fountains, and preventing the
accumulation of manure.
House flies, which serve as intermediate hosts for some species of tape-
worms (table 1), may be controlled as described on pages 130-132.
The prompt and effective disposal of manure, required in house-fly
control, will also eliminate dung beetles, which harbor the immature
stages of certain tapeworms, since they will thereby be deprived of their
source of food supply.
When ants serve as intermediate hosts for tapeworms, they may be
Bul. 674] Diseases of Chickens 141
controlled by the proper employment of a state or federally approved
ant poison. Precautions must be taken, however, when materials poi-
sonous to chickens are used that the birds do not have access to the
poison.
Ground beetles are difficult to control, and the control method varies
with the habits of the different species. When these insects are involved
in tapeworm infections, specimens should be submitted to an entomolo-
gist for identification and advice as to appropriate control measures.
The control measures for stable flies are directed toward their breed-
ing places. Moisture is necessary for the development of the larvae ; dry
material is not suitable for their needs. The more important breeding-
places of these flies can be controlled by promptly removing moist feed
wastes from poultry yards and near-by feed lots and stables, and scat-
tering them to hasten drying or destroying them. Lawn cuttings, weed
piles, vegetables, vegetation washed up on lake shores, and other plant
materials and wastes must not be permitted to accumulate in piles long
enough to ferment and decay. Loosely piled strawstacks, if allowed to
become wet, are important breeding places of the stable fly. Hence, straw
for feeding and breeding purposes should be baled and stored under
cover or the stacks should be rounded up so as to make the top largely
rainproof and the sides nearly vertical.
Treatments. — There is no drug known to be satisfactory for the treat-
ment of poultry-tapeworm infections. Earlier experiments indicated
that kamala was an effective drug for this purpose, but subsequent in-
vestigations have shown that the scolices ("heads") are not removed
and that new segments are promptly regenerated. Since the damage
to the host is caused almost entirely by the scolices, it is futile to admin-
ister kamala to infected birds. Colloidal iodine (see p. 17) has been
recommended for the treatment of tapeworm infections in chickens, but
investigations have shown that this drug removes comparatively few
scolices. No treatment for poultry-tapeworm infections can therefore
be recommended until one that will reach and kill the scolices has been
discovered.
GENERAL CHARACTERISTICS OF ROUNDWORMS
The name "roundworm" is commonly applied to the slender wirelike
worm, Ascaridia galli, which is so frequently found in the intestines of
poultry. This term, however, actually applies to a very large group of
worms, a number of species of which are parasitic in domestic birds.
These worms are unsegmented, usually cylindrical, and elongate in
shape. With but few exceptions the sexes are separate. An intermediate
host may or may not be required.
142 University of California — Experiment Station
THE LARGE ROUNDWORM OF POULTRY
The large roundworm of poultry, Ascaridia galli, as mentioned above,
is a common parasite of the intestines. It is slender and wirelike and
attains a length of from 1 to 4% inches when fully grown. The mature
worms in the intestine deposit eggs which pass out of the body of the
birds in the droppings. After about 10 days' exposure to the air, a young
worm develops in the egg, which, if eaten by a bird, promptly hatches
in the intestine. After about 10 days the resultant worm invades the
intestinal mucosa. Seven days later it returns to the intestinal tract.
Only very exceptionally, and then accidentally, does a roundworm mi-
grate through the lungs. The worm matures in from 5 to 8 weeks after
the egg has been swallowed.
The eggs escaping from the birds are very resistant and will remain
infective in the ground in shaded places for over 3 months. Under experi-
mental conditions, they are rapidly killed by dry, hot weather, even when
buried 6 inches deep in soil exposed to sunlight, but this does not seem
to apply under average farm conditions.
It is believed that the worms probably produce a toxic substance, or
substances.
Symptoms and Diagnosis. — The symptoms of large-roundworm infec-
tion in poultry may become apparent within the first week of infection.
The feathers are ruffled, the wings droop, the birds assume a hunched-up
drowsy attitude and become emaciated and anemic. The appetite is at
first diminished, but later the birds may become voracious. They will
remain stunted, however, despite the large appetite. The young para-
sites may produce marked lesions when they penetrate into the intes-
tinal lining. These lesions cause hemorrhage and inflammation and the
birds become anemic, with marked paleness of the comb and shanks, and
suffer from diarrhea. The birds are unthrifty, generally weak and some-
times paralyzed, and egg production is decreased. In heavy infections,
the worms may cause intestinal obstructions. Young birds are more sus-
ceptible to this parasite than are adults or those which have had a pre-
vious infection. Proper bone development is prevented in the young
birds. Vitamin-A and -B deficiencies make chickens more susceptible to
this worm. Diagnosis is made by finding eggs in the feces by microscopic
examinations or by finding the parasites in the intestine at autopsy
(fig. 55).
Source of Infection. — Large-roundworm infections are acquired by
poultry through consumption of eggs in droppings or soil or by feed
and water contaminated by egg-bearing droppings. Earthworms in con-
taminated soil may mechanically carry eggs and infect chickens which
Bul. 674]
Diseases of Chickens
143
eat them. They do not, however, serve as intermediate hosts as they do
for tapeworms.
Treatment. — Nicotine, although very poisonous for chickens, is a
highly effective drug in the treatment of large-roundworm infections.
When it is combined with certain protective colloids, an effective dose
of the drug can be safely given. Such preparations are readily available
from commercial sources in either pill or tablet form for individual
treatment and in a powdered or granular form to be mixed with the
Fig. 55. — Section of intestine showing roundworms, Ascaridia galli, protrud-
ing from the cut ends. (From Ext. Cir. 8.)
mash for flock treatment. Individual treatment is preferable, because
when mixed with the mash the nicotine may volatilize and be lost and
the more badly infected birds of a flock are likely to have poor appetites
and therefore get a smaller dose of the drug than the more vigorous birds
which need the treatment the least. Such uneveness in dosage from flock
treatment can be partially overcome by separating the weak from the
vigorous birds before the medicated mash is given.
A nicotine preparation of this type consists of a mixture of 6.2 cc
of Black Leaf 40 with 16 grams of a special fuller's earth known as
Lloyd's Alkaloidal Reagent. The powder is packed into no. 2 gelatin
capsules in sufficient quantities to make the filled capsule weigh from
350 to 400 milligrams. Lloyd's Alkaloidal Reagent has the property
of protecting the treated birds from the toxic action of the nicotine and
yet liberating sufficient amounts of nicotine in the intestines to eliminate
144 University of California — Experiment Station
the worms. Most other fuller's earths lack this property and, although
less costly, cannot be substituted. These capsules are available from com-
mercial sources, usually under the name of "University Capsules." The
dose is 1 capsule to a bird, placed well along the throat and, with the
thumb and forefinger on the outside, slid down into the crop. The dosage
is one quarter to one half less for chickens under 8 weeks of age. These
capsules may be poisonous to chickens that are emaciated or that have
been shut in the houses overnight without feed or water and therefore
have empty crops.
Another, though little used, method of giving nicotine is by feeding
a mash containing 2 per cent tobacco dust continuously for 3 or 4 weeks.
The tobacco dust should be a brand marketed in tightly sealed packages
and have a guaranteed nicotine content of 1.5 to 2.0 per cent. Since the
nicotine may be rapidly lost from tobacco dust on exposure to the air,
only a small quantity of the medicated mash should be mixed at a time.
Another effective treatment for large-roundworm infections is carbon
tetrachloride. The drug may be given in capsules, employing the same
technique as for nicotine capsules, the first thing in the morning after
starving overnight. Care must be exercised not to break the capsule in
the mouth since death may quickly result in such an event. The recom-
mended dosage of carbon tetrachloride is as follows : 2 cc for birds 6
months and older ; 1% cc for birds 4 to 6 months ; and % to % cc for
birds under 2 months. For chickens 2 months old or younger, it is per-
haps better to administer tetrachlorethylene in the same dosage as for
carbon tetrachloride. Instead of administering these drugs in gelatin
capsules, they may be introduced directly into the crop by means of a
syringe and a piece of soft rubber tubing. A graduated glass-barreled
5- or 10-cc syringe or a hard-rubber rectal syringe and a piece of no. 5
gauge rubber tubing about 6 inches long are required. The bird's mouth
is opened and the tubing is inserted down the throat into the crop, taking
care to prevent the tube from entering the windpipe. The syringe is then
filled with the drug and attached to the tubing and the recommended dose
is injected. The syringe is detached and the tube is withdrawn very
slowly to permit all of the liquid to run out. Carbon tetrachloride or
tetrachlorethylene should not be administered to birds that have been
fed a diet deficient in calcium.
It is felt that flock treatment is unwise because the dosage cannot be
controlled as it can be when birds are treated individually. Despite this,
however, flock treatment is not uncommon. Flock treatments that can
be used are 1 teaspoon of oil of chenopodium, thoroughly mixed with a
moist mash, for each lot of 12 birds, tobacco dust, or the commercial
nicotine preparations.
Bul. 674] Diseases of Chickens 145
Prevention. — The procedure described for the prevention of coccidio-
sis (p. 92) applies perfectly to large-roundworm control. In the preven-
tion of this infection, it is particularly important that all wet spots in
the yards and ranges be eliminated. Marked results have followed the
installation of gravel pits covered with narrow cleats under all drinking
fountains. Moist soil serves as an incubator for the worm eggs deposited
in the droppings of infected birds. The rotation of runs has been found
to be of considerable value in preventing infection with this parasite.
If young birds can be kept free of the worms for the first 3 months of
their lives by confining them in houses or on clean ground, they are able
to resist infection when placed on infective premises, because of a de-
veloped "age resistance/' to such an extent as to prevent the greatest
injury. This resistance, however, is dependent upon their having re-
ceived a nutritious diet, rich in vitamins.
As soon as the parasites are eliminated by treatment of the birds,
the droppings boards and pens should be cleaned up to prevent re-
infection from worm eggs already on the premises. (The eating of the
roundworms by chickens immediately after elimination is not dangerous
because the eggs contained in the female worms are not infective until
they have been exposed to the air for about 10 days. ) It is best to confine
the chickens to houses with sun porches. If this is impossible, it is advis-
able to remove surface dirt and droppings from the entire yard in the
case of small yards, or, in the case of large yards, from the areas where
the birds congregate immediately after treatment, such as around water
supplies and close around the houses. Plowing such places is profitable.
No known chemical spray is effective in killing roundworm eggs.
THE CECUM WORM
The cecum worm, Heterakis gallinae, is a grayish-white worm from
% to % inch long, found in the ceca, or "blind gut," of the intestines.
Because of their small size, they are easily overlooked or may be mis-
taken for the young of the large roundworm. The eggs (Hg. 56) are
voided in the feces, develop in the open, and reach the infective stage
in 7 to 12 days or longer. These eggs are very resistant. When a bird
swallows an infective egg, it hatches in the intestine after from 1 to 2
hours.
Symptoms and Diagnosis. — The cecum worm is of little importance
in older birds, in which heavy infections are rarely seen, but in younger
ones they may interfere with the normal functioning of the ceca and
in baby chicks may be very harmful and cause death as early as the
tenth day. The particular importance of this worm, however, is that it
is involved in the transmission of blackhead of turkeys.
146
University of California — Experiment Station
Sources of Infection. — Infection with the cecum worm is acquired in
the same manner as described for the large roundworm (p. 142).
Treatment. — Because of their sheltered position in the ceca, these
parasites are very hard to remove. Tobacco dust will remove about 80
per cent of the cecum worms present when it is fed as 2 per cent of the
mash over a period of a month. The tobacco dust should be a brand
marketed in tightly sealed packages and have a guaranteed nicotine
content of 1.5 to 2.0 per cent nicotine. Good results have been reported
with phenothiazine given at the rate of 0.5 gram per bird.
Fig. 56. — Highly magnified eggs of cecum worm (left) and intestinal roundworm
(right), which pass out in the droppings. (From Ext. Cir. 8.)
Rectal injections of oil of chenopodium in a bland oil such as cotton-
seed oil will remove about 90 per cent of the parasites. One tenth of a
cc of oil of chenopodium in 5 cc of cottonseed oil is administered to a
bird weighing 1% pounds. Probably double this dose would be indicated
for a bird weighing 3 pounds or more. The liquid should be thoroughly
mixed and administered with a hard-rubber rectal syringe. The tip of
the syringe should be covered with oil and gently inserted into the
rectum, and the fluid should be injected slowly.
Prevention. — The preventive measures to be taken against cecum-
worm infections are the same as those described for the prevention of
large-roundworm infections (p. 145).
THE GIZZARD WORM
The gizzard worm, Acuaria (Cheilospirura) hamulosa, is a fairly
slender reddish worm, from % to % inch long, frequently found coiled
in the muscular coat of the gizzard. The eggs of this parasite are passed
Bul. 674] Diseases of Chickens 147
out in the feces. If they are eaten by a grasshopper, they hatch, and
the larvae pass through three developmental stages in this intermediate
host. The infective larvae gain access to poultry when the infected grass-
hoppers are eaten. The development in the grasshopper requires 22 days,
and 76 days are required for the worm to come to maturity after being
ingested by the chicken. Certain species of beetles and sandhoppers may
also be involved as intermediate hosts of this parasite.
Symptoms and Diagnosis. — Mild or even moderately heavy infections
do not appear to be harmful. Very severe infections, however, may inter-
fere with the food-grinding function of the gizzard and thus cause
emaciation and weakness. The presence of gizzard worms in an emaciated
bird does not necessarily indicate that the emaciation is due to the effects
of the parasites, and further search should therefore be made for other
causes.
Diagnosis may be made at autopsy by finding the worms beneath the
lining of the gizzard. They are most frequently found near the entrance
of the stomach, and their presence is denoted by blotchy discoloration
of the lining of the gizzard. Diagnosis may also be made by detecting
eggs in the feces.
Treatment. — Because these parasites lie concealed in the muscle tissue
of the gizzard, they are protected from the action of drugs and no effec-
tive treatment is known.
Prevention. — Preventive measures consist in disposing of the drop-
pings in such a way that grasshoppers will not feed upon them, not
allowing the birds to range where grasshoppers are plentiful, and taking
steps to reduce the number of grasshoppers.
Farm practices which are helpful in controlling grasshoppers are (1)
cultivation of infested fields and adjacent ditch banks in the late fall
and early winter to destroy the eggs of the insects; (2) rotation of crops
where alfalfa has been raised continuously for five or more years to
destroy eggs and provide conditions less favorable for grasshopper in-
crease ; and (3) baling alfalfa hay at night so that grasshoppers roosting
in the haycocks will be included in the bale. The latter practice may
decrease the grasshopper population as much as 75 per cent.
Poison baits are very effective in controlling grasshoppers. Any of the
following poisons have been proved to be very effective when mixed with
100 pounds of bran and 12 to 16 gallons of water : 2 pounds paris green
(50 per cent As 2 3 ) or 3 pounds commercial arsenic (98 per cent As 2 3 )
or 2 pounds powdered sodium arsenite (85 per cent As 2 3 ). The soluble
arsenicals, paris green and sodium arsenite, are dissolved in the water
before being mixed with the bran. Commercial arsenic, which is insoluble,
is thoroughly mixed with the bran before the water is added. The efficien-
148 University of California — Experiment Station
cies of these poisoned baits depend upon thorough mixing and the proper
time of application. They should be put out, preferably by broadcasting
on large areas and in small closely set piles on small areas, early in the
morning when soil temperatures are between 60° and 75° F. Since the
maximum feeding period of the insects is when the temperature is
between 70° and 85°, it is not wise to put the baits out when the tempera-
ture is above 85°. Although chickens have a marked tolerance to arsenic,
they should be prevented from feeding upon these poison baits.
The sandhopper is not an insect but is related to the shrimp. It is
small, pale, and shrimplike in appearance and breeds in areas which are
shaded and moist. Where sandhoppers serve as the intermediate host
for gizzard worms, chickens should be kept away from such areas to
prevent infection with this parasite.
HAIRWORMS, OR CAPILLARIA WORMS
Several different species of worms belonging to the genus Capillaria,
called Capillaria worms, or hairworms, have been reported from poultry.
These parasites are all extremely slender and are usually from y 2 to %
inch long, though the largest species may attain a length of 3 inches.
Even the larger ones, however, are difficult to detect at post-mortem
examination because they are slender and imbedded in the mucosa.
Capillaria annulata invades the crop and esophagus ; C. retusa and C.
dubia the ceca; C. longicollis the duodenum; and C. colnmbae, C. col-
laris, C. gallinae, and C. caudinflata the small intestines. The eggs of all
of these species are oval with transparent pluglike structures at each
end. With all but C. annulata the eggs, as soon as they have reached a
certain degree of development after elimination with the droppings,
are apparently directly infective to other susceptible birds without the
intervention of an intermediate host. Recent investigations, however,
indicate that earthworms serve as the intermediate host of C. annulata.
Symptoms and Diagnosis. — Hairworm infections in poultry may seri-
ously affect the health of the birds. Heavy infections produce emaciation,
weakness, and death. Affected birds become depressed, the feathers are
ruffled, and the wings droop. A severe inflammation may be produced
and the droppings may contain pinkish shreds of mucus. Diagnosis is
usually made at autopsy by finding the parasites, though this may be
difficult unless they are very numerous. Detection of the parasites at
post-mortem examination is facilitated by immersing the open section
of the affected portion in water and carefully tearing the lining. Diag-
nosis may also be made by observing the eggs in the droppings.
Source of Infection. — Capillaria-worm infections are acquired by in-
gesting infective eggs on contaminated soil, as described for the large
Bul. 674] Diseases of Chickens 149
roundworm (p. 142). In the case of Capillaria annulata, infection may
possibly be acquired through the ingestion of earthworms.
Treatment. — There is no treatment known that is entirely satisfac-
tory for hairworm infections in poultry. Carbon tetrachloride given,
as described on page 144, in doses of 1 cc, and repeated after about 7 days,
is effective in removing some species of Capillaria worms.
Prevention. — The preventive measures to be taken against hairworm
infections are the same as those previously described for large-round-
worm infections (p. 145). In the case of Capillaria annulata infections,
it may be necessary to avoid contact of the birds with earthworms by
the methods described on page 140.
THE GAPEWORM
The gapeworm, Syngamus trachea, which is extremely rare in Cali-
fornia, is a small reddish worm found in the windpipe. The female,
which is % to 1 inch long, is attached to the lining of the windpipe. The
male, which is seldom more than % inch long, is attached to the female
in copulation in such a way as to form a Y. The male is also attached to
the tracheal wall, where it usually forms a nodule. The eggs deposited
by the female worms pass up the windpipe with mucus, are swallowed,
and expelled from the body with the droppings. After from a week to
a month, according to the temperature, in the open air, a fully developed
embryo capable of infecting a healthy bird is formed. This may be eaten,
while still confined within the egg, by the bird, or it may hatch and be
eaten as a free-living larva. Earthworms feeding on poultry manure may
eat either infective gapeworm eggs or larvae, in which case they may live
for some time in the alimentary canal of the earthworm and thereby be
protected from drying or other unfavorable environmental condi-
tions. The young gapeworm, when eaten by the chicken as a developed,
infective egg or a free-living larva from contaminated soil, feed, or
water, or in the body of an earthworm eaten by a fowl, penetrates
the walls of the alimentary canal and reaches the lungs through some
as yet unknown route. Here it undergoes a period of development,
after which it migrates up the bronchi to the trachea. The trachea is
reached as early as the seventh day after infection and eggs appear in
the feces from the seventeenth to twentieth day. Some investigators
claim that passage through earthworms renders the larvae more highly
infective. The parasites suck blood while attached to the wall of the
trachea.
Symptoms and Diagnosis. — Mature birds rarely become infected with
gapeworms, and when they do the parasites rarely remain in the trachea
for more than a month. Consequently the mature chickens in an infected
150 University of California — Experiment Station
flock show only mild symptoms or none at all. Young chickens, however,
may be severely affected. The trachea becomes partially clogged by the
parasites and mucus, with resultant gasping for air, or gaping, and
spasmodic coughing. The affected birds refuse food and water and be-
come emaciated and weak. Some may die from suffocation.
Treatment. — The mechanical removal of gapeworms from the wind-
pipes of poultry with clipped feathers, horsehair loops, and patented
wire extractors is rather widely practiced but is a slow, tedious, un-
reliable, and somewhat dangerous practice. Of various drugs which
have been recommended for the treatment of this infection, barium
antimonyl tartrate is by far the most satisfactory. The birds to be treated
are placed in a relatively small closed box or other container that is deep
enough to have a space of at least 6 inches above the heads of the birds
when they are standing erect. The container should be small enough to
be tilted from side to side or be equipped with a small electric fan. One
ounce of the finely powdered chemical for each 8 cubic feet of space
within the container is required for each group of birds to be treated.
One third of the total amount of the barium antimonyl tartrate to be
used is put into the box through an opening in the top by means of a
dust gun. The container is then tilted from side to side or the electric
fan is started to keep the powder dispersed in the air and to cause the
chickens to breath more deeply and frequently. Five minutes later a
second third of the powder is introduced and the container is tilted or
the electric fan is started again. In another 5 or 10 minutes, the proce-
dure is repeated with the third portion of the powder. The birds are
released 5 to 10 minutes after the last portion of the powder is blown
into the box.
The barium antimonyl tartrate should be prepared by a druggist or
chemist in the following way : A barium chloride solution is made by
dissolving 244.3 grams of crystallized barium chloride in 800 cc of dis-
tilled water at a temperature of 70° to 75° F. This solution is then mixed
slowly with a warm solution of potassium antimonyl tartrate, made by
dissolving 667.8 grams of the chemical in 1,700 cc of distilled water. The
mixture of the two solutions is then stirred vigorously with a glass rod.
A precipitate is formed and is collected by filtering immediately through
paper with the aid of suction. The precipitate thus collected is washed
with cold distilled water and then with alcohol to facilitate drying. The
washed precipitate is dried at room temperature, since higher tempera-
tures while the chemical is wet may cause decomposition. The yield of
barium antimonyl tartrate is approximately 1% pounds. If properly
prepared, the finished product will pass through a 100-mesh sieve ; other-
wise it must be ground to that degree of fineness.
Bul. 674] Diseases of Chickens 151
Prevention. — The most effective preventive measure is to raise the
young birds apart from the older ones and on land not previously occu-
pied by gapeworm-inf ected birds. Land on which infected birds have not
run for at least two years may be used without immediate danger of
losses from gapeworm infections. Sandy, well-drained soil is highly
desirable, since soil of that type is not favorable for development of
gapeworm eggs and larvae and is less likely to be infested with earth-
worms. All moist localities and situations such as wet grass should be
avoided to prevent feeding upon earthworms. Confinement of the birds
to houses with sun porches and the regular removal of droppings and
contaminated litter at least at weekly intervals would afford ideal pro-
tection against this parasite.
Turkeys of any age are susceptible to gapeworm infection but they
show no symptoms and therefore are dangerous carriers of the disease.
Consequently turkeys should not be kept with chickens nor should
chickens be placed on land that has been occupied by turkeys.
Infected birds that cannot be treated should be killed and destroyed
by burning.
50jn-12,'42(2398)