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