UNIVERSITY OF CALIFORNIA AGRICULTURAL EXPERIMENT STATION BENJ. IDE WHEELER, President COLLEGE OF AGRICULTURE thomas fohsyth hunt, dean ano director __ _j,_ . p- v H. E. VAN NORMAN, Vice-Director and Dean " tnlXLLt Y University Farm School CIRCULAR No. 155 September, 1916 BOVINE TUBERCULOSIS By C. M. HARING In view of recent legislation in this state concerning the sale of dairy products, which becomes effective October 1, 1916, it has been deemed advisable to publish some fundamental facts concerning bovine tuberculosis. (See California Statutes, 1915, p. 1478.) This station has no responsibility concerning the new law. All communications concerning it should be addressed to the State Dairy Bureau or to the State Veterinarian. (See note bottom p. 2.) Cattle are the most susceptible of all animals to tuberculosis. Hogs also contract the disease easily when fed on infected milk or when running in fields with tuberculous cattle. Poultry are some- times affected with a form of tuberculosis, as are also household pets. In fact, there is no kind of animal that will not develop the disease, although horses and sheep are seldom infected. Tuberculosis is the most serious, infectious disease of man. The bovine type of bacillus rarely causes the lung form of the disease in adult human beings, but it is responsible for certain types of tuberculosis in infancy and childhood. The percentage of cases of the bovine type occurring among children depends on local conditions, and is variously estimated. The maximum found in any locality has been 25 per cent. The cause of this disease in children is infection transmitted through raw milk and cream. It may also be present in other dairy products, such as butter, fresh cheese, skimmed milk and buttermilk. THE ECONOMIC ASPECT OF BOVINE TUBERCULOSIS The losses due to the prevalence of this disease in farm animals are not as apparent as they are important. It is no uncommon thing for a veterinarian to find 70 or 80 per cent of the cows in a herd diseased without much loss being evident to the owner. Losses from deaths due to tuberculosis seldom become serious in a herd until the disease has spread to a majority of the animals. Often the first inti- mation that anything is wrong comes to the owner through the report from the abattoir that cattle from his ranch have been condemned as unfit for food on account of tuberculosis. Reports of meat inspectors in San Francisco show that the number of tuberculous cattle coming from certain sections increased from nine-tenths of one per cent to nine per cent in five years. Recently the proportion of hogs condemned by meat inspectors on account of tuberculosis has increased markedly. This is an added indication of the spread of infection in cattle since the cow is the chief source of tuberculous infection in swine, the disease being transmitted to swine through milk or buttermilk from tuberculous cows, through infected cattle corrals or by feeding uncooked carcasses to the hogs. The enormous losses due to this disease are a tax upon every pint of milk and every pound of beef sold. That the aggregate loss to the state is enormous cannot be doubted, but, on the other hand, the loss to the individual owner is seldom so great as to make him ready to adopt measures involving a great deal of immediate trouble and expense, in order to secure eventual complete freedom from the disease. WHAT ARE THE SYMPTOMS OF TUBERCULOSIS IN CATTLE? There is no symptom that can be relied upon with certainty. A herd may be badly infected and yet none of the cattle show symptoms of ill health. Tuberculosis may attack almost any organ of the body, but until it has progressed to an advanced stage there may be no visible signs. Following are some of the more important symptoms suggestive of the disease, but it should be understood that these may also be caused by other diseases: Unthriftiness. — In advanced stages of the disease the coat may become rough, the hair failing to shed readily with the change of The new law gives this alternative: either to pasteurize the milk and cream sold at retail or to submit the cattle to an official tuberculin test. Dairymen who sell in bulk to the wholesale trade need not have their cows tested or install a pasteurizer. The responsibility of pasteurization rests on the creamery. In cities or counties having a dairy inspection service all milk retailed must be graded and properly labeled. Every cow owner who intends to retail any unpasteurized milk or other dairy product, except cheese, should write to The State Veterinarian, Sacramento, California, requesting that his cows be tuberculin tested. Those intending to retail in any city or county having a dairy inspection service should file a duplicate request with the local health officer. After filing these requests the dairy- man is not liable under the provisions of the law until the State Veterinarian or his representative shall be able to make the required tests. Pasteurization on the dairy ranch will in most cases be impracticable. Any dairyman who is contemplating the installation of pasteurization equipment is advised to confer with the officials of the State Dairy Bureau or with the chief dairy inspector of the city in which his products are used, for many cities refuse to allow milk to be sold unless it has been pasteurized within the cites. It is, moreover, illegal to repasteurize milk to be sold for human consumption. seasons. The skin loses its suppleness and feels harsh and thick and is difficult to fold when grasped by the hands. This is especially noticeable in the neck or flanks. This condition is known as "hide- bound." The debilitated expression of the eyes and face, the bristling hair, arched back and tucked-up abdomen are symptoms which may or may not be present in advanced tuberculosis. Loss of Flesh. — A gradual falling away should always be a cause for suspicion, but leanness is a common characteristic of good dairy cows ; therefore a knowledge of the normal for each individual animal is necessary before judgment may be passed on this symptom. The owner or milker is often better qualified to decide these cases than a veterinarian who has never seen the animal before. Cough. — This symptom is only present when the disease is attack- ing the lungs or some part of the breathing organs. It is usually rather subdued and infrequent and may occur only when the animal is driven or when she gets up after having lain down for some time. Tubercu- lous cows do not appear to cough up anything. This may be because they cannot spit. Most of the material coughed up from the lungs is swallowed, but many tuberculosis germs escape from the mouth in the spray. Nasal Discharge. — A slight discharge of pus from the nostrils may occur in cattle with advanced tuberculosis of the lungs. This discharge is often concealed by the frequent licking of the nostrils and would be overlooked by any but a close observer. Enlarged Glands. — Hard, painless swellings in cattle are apt to be due to tuberculosis. These are especially liable to occur in front of the shoulder, in the flank or groin, or in the region of the throat. Swellings under the jaw proper are more often due to actinomycosis or to the penetration of the tissues by foxtail beards. Tuberculous growths often develop in the throat or back of the jaws so as to produce a roughened sound in breathing. Hard Lumps in the Udder. — When tuberculosis attacks the udder no change can be detected at first, but after a time hard lumps can be felt in some parts of the organ after it is milked out. Milk from such an udder must not be used. Chronic Bloating. — Sometimes the diseased glands in the chest prevent the usual passage of gas from the paunch to the mouth by pressing on the gullet. The resulting bloat is recurrent or chronic and easily distinguishable from the acute bloating caused by green alfalfa. Diarrhoa. — Looseness of the bowels or "scouring" is seen in ad- vanced stages, particularly when the disease is generalized. This kind of scouring does not yield to treatment. WHAT TUBERCULOSIS IN CATTLE LOOKS LIKE When the carcass of the cow affected with tuberculosis is opened, the disease may be found in any part of the body, but it is usually located in the lymph glands of the chest, throat, or abdomen. The exteriors of the tubercles often look like masses of pearls and on this account years ago the disease was called pearl disease of cattle. Tissues showing lesions of tuberculosis in cattle and hogs can be seen in the veterinary exhibits of the College of Agriculture at Berkeley THE CAUSE OF TUBERCULOSIS IN CATTLE Although there is much that is yet to be satisfactorily explained concerning the way in which cattle contract tuberculosis, it is definitely known that the disease results from the invasion of the tissues of the body by bacteria. 2 The bacilli of bovine tuberculosis are believed to exist only in the tissues of diseased animals and in their excretions, or on substances contaminated by these excretions. Except under the most favorable conditions they do not multiply outside the body, although if not killed by sunlight or disinfectants they may survive in dirt for several months. 2 The Bacillus tuberculosis (Koch) belongs to that genus of microscopic- plants known as discomyces or mycobacteria. When the infected tissue is smeared on a glass slide and properly stained the bacteria may be seen by means of a high-power microscope as slender, slightly bent rods, .00006 to .00015 inch in length by .00001 to .00002 inch in diameter. These organisms do not stain readily with ordinary aniline dyes. Once stained with carbol-fuchsin, however, the dye is retained even after the application of alcohol or 30 per cent sulphuric or hydrochloric acid. For this reason tubercle bacilli and a few other species of bacteria are classed as ' ' acid and alcohol fast, ' ' as distinguished from those which lose the color of their stain when treated with alcohol and acid. Tubercle bacilli are not readily obtained in pure culture from tuberculous tissues. The usual method is to inoculate guineapigs and from their diseased tissues inoculate a large number of tubes containing egg media. When once started to grow on egg media the germs can be transferred and more readily cultivated on glycerine bouillon. Tubercle bacilli of cattle, man and birds may be distinguished from one another by appropriate laboratory methods. A culture of bovine tubercle bacilli may be distinguished from the human type by the fact that it grows feebly and the acidity of the bouillon decreases, while the growth of the human type is luxurious and the media, although first reduced in acidity, become more and more acid with the age of the culture. The human and bovine types appear to be equally virulent for guineapigs. The human variety is not often fatal to rabbits or cattle and the tissue changes which it produces in these are very slight and restricted to the point of inoculation. The bovine variety when inoculated into cattle or rabbits is usually fatal. HOW THE DISEASE SPREADS When an animal first becomes infected there is usually no danger to other cattle, but sooner or later tuberculous cattle begin to give off the germs of the disease. The germs escape through the mouth and nose, the bowels, the milk and with discharges from the genital organs. When the disease is located in the lungs and discharges into the air tubes, pieces of diseased tissue and millions of germs are liberated and coughed up. Most of these are swallowed and passed out in the manure. This is the chief way in which the germs are discharged from diseased cattle. When the germs are being given off in any of these ways, the disease is known as open tuberculosis. Cattle in advanced stages of the disease usually have open tuberculosis. The high percentage of tuberculous cattle and hogs on certain ranches has been found to be due to the failure of the owners to remove promptly animals that develop visible indications of the disease. Germs discharged from the mouth and nose are coughed up from the lungs and are sprayed over the food in front of the cow or are carried in the air for a time until they fall to the ground. Cows in adjoining stalls may take in these germs in the air they breathe or in the food they eat, and so contract the disease. Germs discharged from the bowels are mixed with the manure and may infect cattle and hogs that are allowed to pick over the dung heap. The practice of having hogs and cattle together in the same yard often results in the infection of the hogs, if any of the cattle are affected. Manure containing tuberculosis germs may easily infect the milk. Particles of dried manure may fall into the milk pail from the skin of a dirty cow or be accidentally flicked off from the tail and fall into the milk. Straining the milk afterwards only removes the larger particles. The smaller ones, including the germs, remain in the milk. When the udder is tuberculous, the milk contains the germs in vast numbers. Although such milk may look and taste perfectly good, it may transmit the disease to young animals. Hogs and calves are readily infected by it. It is also dangerous to children. When all the tuberculous areas in the body are so situated that no germs are being given off or discharged in the secretions, as above described, the condition is known as closed tuberculosis. Such animals do not transmit the infection until they become so diseased that the tuberculous areas open into a passage leading to the exterior of the body. Many infected cattle never develop open tuberculosis, but there is no way of determining accurately in living cattle which are the open cases and which are closed. In badly infected herds a careful physical examination by a veterinarian will eliminate a certain pro- portion and a much larger proportion may be detected by the inocula- tion of guinea pigs. This latter procedure, however, is impracticable under average dairy conditions and it will fail to detect those cases which do not happen to discharge germs at the exact time the sample is taken. Rate of Development. — Individual animals exhibit the widest vari- ation in the duration of the disease. In the majority the disease pursues a leisurely course, consuming years before causing death. Most infected cattle are fattened and sold for beef, but some develop a rapidly fatal type. Its onset is always unobtrusive and its progress is so gradual that its presence does not cause apprehension. Losses are so evenly distributed in point of time that they do not excite serious alarm, as do other less destructive diseases of the pestilential type which kill many suddenly. The rate of spread in a herd is vari- able. In some herds which are known to have a few reacting animals the disease does not seem to spread. Perhaps this is due to the fact that few, if any, of these happen to be open cases. On the other hand, in certain instances under observation the disease has been introduced into clean herds and in a few months, through the development of open cases, a large proportion of the cattle have become reactors. The feeding of infected milk to calves, particularly unheated mixed skim- milk returned from the creamery, usually results in speedy infection. HOW A HEED IS INFECTED Tuberculosis may be introduced into a healthy herd in a number of ways: 1. By the purchase of a bull or other animal that is infected with the disease. This animal may be apparently healthy at the time of purchase, but if previously exposed the disease may develop and spread to other cattle. Where a healthy herd is being maintained, animals should only be bought subject to the tuberculin test and even this precaution may fail if the herd from which they come is badly infected. 2. By feeding calves with milk, buttermilk, or whey that has come from tuberculous cows. A farmer may have a healthy herd, but, if he brings home skim-milk from a creamery and feeds it to his calves, the disease, if present in the milk, may be transmitted to them. Such milk should be rendered safe by boiling or pasteurizing. 3. By showing cattle at fairs and exhibitions where proper care is not taken to keep out diseased stock, or to disinfect the stables. 4. By shipping animals in cars that have not been disinfected, as these may have recently carried diseased cattle. 5. By allowing the cattle to graze with diseased ones, or to come into contact with them over fences. 6. When the cattle are permitted access to small ponds, water holes, or troughs, these may become badly contaminated with infected manure from "open cases/' The rapid spread of the disease on certain ranges is believed to be due in part to infected water. HOW THE PRESENCE OF TUBERCULOSIS INFECTION MAY BE DEMONSTRATED The tuberculin reaction is the best method at present available for the recognition of tuberculous infection in cattle. There are several reasons why this special test is necessary. Unless cattle are very badly diseased they seldom show symptoms of ill health. Almost any organ of the body may be attacked, but until the abnormal pro- cess has progressed far enough to interfere seriously with some func- tion no symptoms can be detected. The thickness of the skin and chest wall makes it difficult to detect a diseased condition in a cow's lung by listening to the sounds made in breathing, whereas this is comparatively easy in human beings. Next to the tuberculin test, a careful physical examination by a trained veterinarian is the most practicable method of diagnosis; in fact, the tuberculin test should always be supplemented by such an examination, since badly diseased cattle often do not react to the test. Other methods which occasionally may be useful in detecting the disease are microscopic examination of diseased tissue, exudates from the pulmonary, intestinal or urinary tracts and pus from abscesses, or animal inoculation with such material. The latter is a much more certain test than a direct miscroscopic examination. Guineapigs are usually employed for this purpose. What is Tuberculin and its Reaction? Tuberculin is the filtered, sterilized and preserved glycerine bouillon upon which tubercle bacilli have grown. It contains no germs and is harmless to cattle even in increased dosage. In tuberculous cattle it produces a temporary effect or reaction. The living tissues of tuberculous persons and animals are sensitive to tuberculin. This sensitiveness is most marked in the tis- sues that are actually invaded by the germs, but it also exists to some extent in the other tissues of the body which contain bloodvessels. The living tissues of individuals not infected with tuberculosis show no sensitiveness to tuberculin. 8 When tuberculin is injected into the vascular layers of the skin of a tuberculous cow a swelling will usually follow. When dropped on the eyeball an exudate of pus may result. When injected into the skin or tissues in sufficient amount a feverish attack comes on about eight to twenty hours after the tuberculin is administered, lasts a few hours and then subsides. These symptoms are called reactions and animals which show them are called reactors. The value of the test lies in the fact that diseased animals react, while healthy ones do not. There are several ways of testing with tuberculin. The methods which are most practicable are the intradermal, the subcutaneous and the ophthalmic. Each of these methods has certain advantages. The conditions under which the testing is to be performed should be the guide in choosing the method. The successive or combined use of all three tests on the same animals gives the highest accuracy in diagnosis. THE INTRADERMAL METHOD The tuberculin is injected into the deeper layers of the skin, or into the sub- dermal tissue immediately adjacent, in % to % c.c. amounts, depending on the concentration of the tuberculin used. A hypodermic syringe with a short needle- point should be used. Such a syringe should have a 25 or 26 gauge needle with a point three-sixteenths to one-quarter of an inch in length, similar to those used by dentists for injecting local anesthetics. The most suitable place to make this injection is one of the folds of the skin on the under side of the base of the tail. Standing against the right flank of the cow, the left subcaudal fold is grasped between the thumb and the first two fingers of the left hand and the needle inserted into that portion of the skin held between the thumb and finger. The dose, if properly placed, can be felt as it is expelled from the syringe in the layers of the skin, where it remains as a small lump in the skin after the needle has been removed. The mistake of trying to inject as near the surface of the skin as possible should be avoided. It is difficult to inject into the layers of the epidermis and an injection into this part of the skin is of little diagnostic value. In case the needle is of the proper length, namely, one-quarter of an inch, there is little danger of going completely through the skin. When the proper point in the subcaudal fold is selected, it makes little difference whether the point of the needle is in the dermal or in the subdermal connective tissue. It is well to inject at a point on the fold about two and one-half or three inches down the tail from the anus, since elsewhere reactions are not so easily per- ceived, and at this point the bone and solid tissue of the tail form a background which renders the local reactions prominent. The skin of the lower eyelid has been used in some of the tests at this station, but the subcaudal fold has been found to be more satisfactory. This method of injecting the tuberculin intradermally into the lower eyelid is called the intrapalpebral test and has been advocated by certain veterinarians as a cleaner and more convenient way to administer the test. It is, however, loss practicable on account of the additional help needed. The reactions are at 9 times difficult to distinguish from the normal fullness of the lower eyelid, and on this account it is necessary to examine and compare the tissues beneath both eyes in deciding a reaction. It is a difficult method to use on range cattle. The Beaction to the Intradermal Injection in Cattle. A positive intradermal reaction is indicated by a thickening of the subcaudal fold or by the appearance at the point of injection of a characteristic sensitive swelling varying in size from that of a pea to that of an orange. The swelling may be either soft and oedematous or hard and inflamed. The majority of reactions are seldom clear before the twelfth hour and when testing in infected herds new reactors continue to appear until the seventieth hour. In some instances we have observed that the early local reactions disappear before the forty-eighth hour, while in several cases we noted reactions which did not appear until the ninetieth hour. In order to be certain of every case, observations must be taken at least twice, preferably about the thirty-sixth and seventy-second hours. If only one obser- vation can be made, it should be on the seventy-second hour. Small indurations at the point of inoculation about the size of the head of a parlor match frequently occur in normal non-reacting cattle, but any larger than this which persist to the seventy-second hour should be considered a positive reaction. In judging a local swelling, the observer should depend more upon the shape, appearance, tenseness, sensitiveness and location with respect to the exact point of injection than upon actual measurements. Only experience can teach an operator how to be certain of a positive reaction when the local swelling is small. This is especially true when tuberculin containing glycerine has been used. Usually tuberculous cattle also show a temperature reaction to the intra- dermal injection. THE OPHTHALMIC METHOD An assistant should grasp the animal by the nose and turn the head at an angle so that the operator may drop one or two drops of the tuberculin directly upon the eyeball. A small hypodermic syringe with the needleshank broken or filed off is more suitable for this purpose than a medicine dropper. The eye is then closed for a few seconds by pressure from the palm of the hand. A pre- liminary instillation to render the eye sensitive should first be given as just described, but it is not necessary to take observations concerning the results of this. The second or test instillation is made in the same eye in from three to fourteen days. The reaction in tuberculous cattle usually sets in by the eighth hour. In cattle whose eyes have been sensitized by a previous instillation it may set in by the third hour. It manifests itself by a purulent exudate which accumulates at the inner corner of the eye and usually runs down the face. This sometimes dries up and drops off in a few minutes, so that the evidence of the reaction may quickly and entirely disappear, although occasionally pus discharge can be seen for several days. Although the results of the test are usually apparent by the twelfth hour, they may occur as early as the third hour, and observations should be made as frequently as practicable from the third to the twenty-fourth hour. The test is only satisfactory when cattle can be kept tied or confined in stanchions under shelter for a period of at least 16 hours, except in the case of cattle which show a reaction before that time. It is advisable not to feed unchopped hay on account of the possibility of wiping off the exudate. 10 THE SUBCUTANEOUS METHOD This method consists in injecting one to four cubic centimeters of tuberculin beneath the skin of the neck or shoulders. The reactions consist of a feverish attack, characterized by a rise in temperature and occasionally by symptoms of depression, shivering, bristling hair, ceased rumination and looseness of the bowels. In some cases these symptoms are noticeable, while in others they do not appear at all. The temperature rise after the injection of tuberculin in a tuberculous animal, however, is seldom absent and usually occurs between the eighth and the twentieth hours. The normal temperature of a cow varies between 100° F. and' 103° F. Calves and fat stock may range to 103.5° F. During the tuberculin reaction the temperature rises to a height varying be- tween 103° F. and 108° F. The positive tuberculin reaction generally shows a regular rise, the temperature remaining at the highest point for a short time, then falling gradually to normal. The highest point is usually between 104° F. and 107° F., but in some reactors may be as low as 103.2° F. and in others reach 108° F. It is not always an easy matter to distinguish between some reactions and the variations in temperature in the normal healthy animals. The temperature of cattle is quite erratic, being influenced by the weather or any change in the usual routine of handling. During the severe north winds which sometimes occur in central California the temperature of herds of normal cattle may average over 103.5° F. Directions for Talcing Temperatures. Continue the normal temperatures until they drop below 103° F. Take subsequent temperatures every two hours be- tween the eighth and twentieth hour. If any subsequent temperature reaches 103° F., take another temperature in one hour. If at the twentieth hour after injection any animal shows a rise in temperature above previous temperatures for the day continue taking the temperature as long as the rise is continued. WHEN THE VAEIOUS METHODS SHOULD BE USED The intradermal method is the form of the test which will be used in most cases by the State Veterinarian in enforcing the new dairy law. Since the reaction to tuberculin when injected intradermally depends upon a swelling at the point of injection and not on a rise of temperature, it is to be preferred to the subcutaneous method under all conditions which are liable to modify the tuberculin temperature curve. It can be satisfactorily applied to calves and wild range cattle and is especially useful in testing cattle during the hot season in the interior valleys of this state under conditions rendering both the sub- cutaneous and ophthalmic methods of testing unsatisfactory. It excels these methods in economy of time, labor and materials. The ophthalmic method is desirable where favorable arrangements can be made for housing the cattle during the test and when there is time to repeat the test. The chief advantages are: (1) It does not render the cattle insensitive to subsequent tests by other methods. (2) 11 It will cause reactions in tuberculous cattle that have been "plugged," i.e., treated with tuberculin to render them insensitive to a test. (3) The technique of the test is simple and the interpretation of the re- actions requires less skill and experience than the intradermal reac- tions. (4) In case of doubtful reactions, the test may be repeatedly administered to the same animal. The subcutaneous method is the original way of testing and is the only method officially accepted in all states and by the United States Department of Agriculture. On account of its extensive use for many years its possibilities and limitations are understood by nearly all veterinarians and by many stock owners. Its proper application re- quires less practice and the results can be more readily interpreted by the inexperienced. The record of the reactions can be graphically expressed in the form of a temperature curve. The use of this method is especially to be commended in infected herds as an additional pre- caution to be applied following the use of the other two tests. LIMITATIONS OF THE VARIOUS METHODS OF TESTING No form of the tuberculin test distinguishes between severe and slight cases, nor between those that are spreading infection and those that are not inconvenienced by the disease and are not infecting others. The test is so searching that extremely slight infection will cause the animal to react. In cattle reacting to the test the infection may occa- sionally be so recent and the changes so slight that the ordinary methods of post-mortem examination fail to demonstrate the presence of tuber- culosis, since the lesions may be microscopic in size. If a reaction does occur, tuberculosis is certainly present, although it may be very slight ; but if no reaction occurs care must be taken, for there is still a possibility that the disease is present. Following are some of the factors to be considered : (1) The animal may not react if very extensively tuberculous, but in such cases physical symptoms will usually indicate ill health. (2) The reaction does not occur during the period of incubation of the disease; in infected herds a second test should, therefore, be made within six months. (3) Cows that have once reacted may fail to do so upon subsequent tests, the lesions being encapsulated or arrested, but frequently in such cases the disease is known to have become active again after a time. (4) The possibility of the cattle having been "plugged" by the previous injection of tuberculin must sometimes be taken into account. 12 The discovery that the ophthalmic test will usually cause reactions in ' ' plugged ' ' tuberculous cattle has somewhat decreased the importance of the chance of error. Dr. James Law in his treatise on veterinary medicine gives seventeen conditions under which he believes the sub- cutaneous method to be unreliable. In most instances these do not apply to the intradermal or ophthalmic methods. Only those who have been especially trained and, in addition, have had considerable field experience can secure accurate results in testing badly infected herds. Each form of the test has its special value and limitations. Nevertheless, the tuberculin test must be looked upon as the most accurate and valuable means at hand to assist in the diagnosis of tuberculosis. (5) Frequently tuberculous animals have been observed to react to one form of test and fail to respond to the others. This peculiarity in some infected animals has not been satisfactorily explained, al- though the proportion of such animals is sufficient to be of consider- able practical importance. A large proportion of such cases may be due to lack of sufficient care to observe the effects of the tuberculin upon the individual, i.e., failure in the subcutaneous test to take suffi- cient temperatures ; failure in the intradermal test to inspect the point of injection at proper intervals ; failure in the ophthalmic test to keep the animals under proper environment and constant observation. THE COMBINED OE FOLLOW-UP SYSTEM OF TUBERCULIN TESTING In badly infected herds the maximum efficiency by the ordinary technique used by veterinarians in routine work probably averages less than 90 per cent for any one method of tuberculin testing, the errors being due chiefly to failures to secure or detect reactions in the tuberculous cattle. Before accrediting a previously infected herd as free from tuberculosis, the veterinarian should use the combined methods. The following procedure, which we have called the follow- up system, is advised : (1) Apply the ophthalmic test two times at intervals of about one week, the results of the second test being watched with great care. (2) Follow this by the intradermal test, using y 5 c.c. of a strong tuberculin solution, such as 10 per cent precipitated tuberculin, and take temperatures as in the subcutaneous test above described. Ex- amine the point of injection for local reaction at about the 36th and 72nd hours. In case the herd is to be retested by the subcutaneous method, the taking of temperatures may be omitted and the intrader- mal dose reduced to Mo c.c. of ordinary veterinary or 5 per cent pre- cipitated tuberculin. 13 (3) After a lapse of at least six weeks, 3 the subcutaneous method may be applied to all animals that have not been removed by the pre- vious tests. The additional precaution of occasional ophthalmic tests is sometimes also desirable. (4) All herds having reactors should be retested every six months and herds free from reactors annually. This station has found the above system desirable in building up a clean herd where the only supply of animals was from very badly infected herds. For a number of years the alternate use of the intra- dermal and subcutaneous methods semi-annually has been in vogue in most certified dairies in this state, and whenever an unusually large percentage of reactors has been found the follow-up system has been used. DISPOSING OF REACTING CATTLE Slaughter for beef under inspection is the recommended method of disposal of all reacting cattle which show no visible signs of the disease, except in those cases where the beef value would be very much less than the dairy or breeding value. The method formerly and most commonly employed of disposing of reacting animals was by slaughter and burial. Where this wasteful method has been employed the re- sults have been discouraging; even when the state recompensed the owner in part for the loss of his stock, it has been unsatisfactory. A large number of reacting animals are usually but slightly diseased. They readily take on flesh and can be fattened and used for beef. The university practices what it preaches in this regard. They must be carefully examined by a veterinarian when killed and if the disease is found to be extensive the carcass must be condemned. The federal government meat inspection regulations admit the use of meat for food from animals that show limited lesions of tuberculosis, for it is recognized that such meat does not contain tubercle bacilli and, besides, the common procedure of cooking meat is a further safeguard against danger. The zeal of various health officials in demanding the waste of the flesh of every reacting animal has been a great drawback to the control of tuberculosis through developing opposition. THE CONTROL OF TUBERCULOSIS In the application of any methods for the eradication or prevention of tuberculosis certain important characteristics of the disease should be borne in mind : 3 The intradermal test appears to have some modifying effect on a subse- quent test by either the intradermal or subcutaneous methods, but this is not so pronounced as that produced by the subcutaneous injection and retests may safely be made in six weeks. 14 (1) Its indigenous nature. Bovine tuberculosis is so firmly rooted and so widespread among dairy cattle that no important dairy com- munity, the Island of Jersey excepted, is free from it. So far as is known, no dairy section when once infected has been able to eradicate the disease completely. The possibility of eradicating bovine tuber- culosis from individual herds has been demonstrated beyond all ques- tion, and the obstacles which have prevented the successful accom- plishment of this in communities, states, or countries have been due to the unwillingness of the cattle owners to make the necessary finan- cial sacrifices. (2) Its specific nature. Tuberculosis does not develop sponta- neously. The cause of the disease is the bacillus of tuberculosis, which exists only in the bodies of tuberculous animals and in their secretions, or in substances contaminated by them. In-and-in breeding cannot produce it. Dark, filthy, badly ventilated stables, poor food and crowded conditions may contribute to its rapid spread among cattle, but the disease does not originate in an animal, no matter how bad its environment. It must be exposed to the disease germs to contract the disease. (3) Its infectious nature. Tuberculosis is most readily communi- cable. This point, in connection with its specific nature, cannot be too strongly emphasized. The disease results from the association of tuber- culous cattle with healthy ones and under such conditions will spread in spite of every sanitary precaution. It is a mistake to assume that the disease cannot thrive and multiply among dairy cattle kept under ideal conditions. The invigorating influence of fresh air and sunshine, wide, well watered pastures, well ventilated, ideally constructed, im- maculately clean barns, and abundant and well balanced rations will not stop, although they are likely to retard the spread of the disease. It is among some of the best kept herds that the disease has been found to be alarmingly prevalent. Contact, direct or indirect, is the chief way in which the disease is disseminated. Calves most frequently contract the disease from the milk. Calves and hogs fed on pasteurized milk from tuberculous cows soon become infected. STATE MEASURES TO CONTROL BOVINE TUBERCULOSIS The responsibility for the spread of bovine tuberculosis rests with the owners of infected cattle, but it is the duty of the state, from economic as well as public health reasons, to aid them in the difficult task of controlling the increase of this disease in live stock. In this state, up to the present time, practically nothing has been done and 15 the law soon to be in force is intended purely as a public health measure. Unfortunately, but unavoidably, the early efforts to eradicate bovine tuberculosis were undertaken without a full appreciation of the magnitude of the problem. In some states having compulsory tuberculin test laws the scheme of indemnification by the state was introduced. With funds that it has been possible to get from legis- latures the work has made no progress and with few exceptions tuber- culosis has kept pace with the puny efforts directed against it. The attempts by states to eradicate the disease in cattle by tuberculin testing and the slaughter of all reacting animals have proved imprac- ticable. SUPPRESSION OF THE DISEASE BY THE COW OWNERS The first step in getting rid of the disease is to find out how many of the herd are affected. This is done by applying the combined tuberculin tests with careful physical examinations. The proper course to pursue will depend largely upon the proportion of reactors found. Suppose a few cattle react, say less than 15 per cent. Indi- vidual owners of such herds are advised to start to exterminate the disease immediately. The steps necessary are : 1. Isolate all the reactors, including cattle which may have given doubtful or questionable reactions. Non-reactors which on physical examination show any symptoms attributable to tuberculosis must be included. It is unquestionably a good policy in herds showing such a low percentage of infection to sell the reacting cattle for beef, or to establish a separate infected herd, the milk of which is pasteurized. 2. Thoroughly clean and disinfect premises. 4 Since chemical dis- infectants in dilutions practicable for the liberal use required in dis- infecting stables and corrals act very slowly in killing tubercle bacilli, most dependence should be placed on thorough cleaning, painting and whitewashing. Particular attention should be given to the absolute removal of all manure, the smallest particles of which may harbor innumerable tuberculosis germs. 3. Retest the herd in two or three months by applying the ophthal- mic method at least twice and immediately remove all reactors and again clean and disinfect. Every six months apply either the intra- dermal or subcutaneous test. In such semi-annual testing we prefer to alternate the subcutaneous and intradermal methods. 4 Literature describing the methods of stable disinfection may be obtained free from the College of Agriculture, University of California, Berkeley, California. 16 4. Additions to the herd should be subjected to the tuberculin test and, in addition, should come from herds that are comparatively free from reactors. The purchase of cattle from badly infected herds, even when they pass the tuberculin test, is unsatisfactory. When pur- chasing cattle it is usually impossible to find any for sale from herds known to be free from tuberculosis, but in several dairies under the supervision of this station it has been found entirely practicable to follow the rule of purchasing only from herds having less than 10 per cent of reactors. Since the adoption of this 10 per cent rule the proportion of reactors at each semi-annual test has been much less. Owners of herds that are comparatively free from tuberculosis should make few purchases, but depend on the raising of the calves. There is great danger in buying non-reacting cattle from infected herds — that is, animals that have been exposed to infection. The unit to deal with in buying cattle is the sound herd rather than the non-reacting individual animal. In the dairies near cities, where it is not economical to raise the calves and the milking herd is kept up by the constant purchase of "springers," or fresh cows, it will be impossible to keep the herd free from reactors, although in certain dairies of this class the number of reactors is kept down to an average of about 3 per cent by semi-annual testing and the prompt removal of reactors. The Suppression of Tuberculosis in Moderately Infected Herds. In herds having from 15 to 50 per cent of reactors the best course to pursue is not as definitely known as in badly infected herds, where it is hopeless to try to separate the infected from the healthy and where dependence must be placed entirely in the raising of healthy young stock; or in slightly infected herds, where it is always advisable to stamp out the disease by repeated tuberculin tests and the prompt removal of all reactors. In moderately infected herds there are many healthy cattle which can be saved from infection and it is undesirable to leave them with the infected herd, while, on the other hand, the economic sacrifice entailed in the sale of all reacting cattle often would be a far greater loss than any that would be caused by the disease itself. The so-called Bang System is sometimes advisable. The method is as follows : 1. Test every animal in the herd with tuberculin. 2. Remove the reacting animals and keep them isolated so that the disease cannot be transmitted to the healthy animals either by contact, by the attendants, or by the same feeding or drinking utensils. 17 3. Clean, disinfect and paint or whitewash the stable to prevent transmission of the germs left by the infected animals. 4. Test the healthy herd with tuberculin regularly to detect any cases that may develop and remove such animals before they spread the disease. Disinfect again. 5. Remove the calves from the diseased herd at birth and feed them milk from the healthy cows or milk from the diseased cows after thorough pasteurization by heating to 160 ° F. for 20 minutes. As the sound herd is replenished, the isolated cattle may, if de- sired, be fattened and killed for beef under proper inspection. When new or non-infected buildings and corrals and well separated pastures are available for housing the non-reacting cattle this Bang System or some of its modifications may be attempted. Through the failure to guard against the limitations of the tuberculin test by repeated re- testing, or through inadequate separation of the two herds, many, after trying this system for years, have failed to make headway in building up a healthy herd. In many instances it will be cheaper for dairymen in whose herds over 35 per cent of the animals react to keep the entire adult herd as one unit and for a time devote all efforts to protecting the new-born calves. In such cases a frequent physical examination of the infected herd is desirable in order to eliminate clinical cases as soon as possible after they develop. In herds having less than 35 per cent reactors it may sometimes be desirable to try to stamp out the disease by repeated tuberculin testing and the prompt removal of all reactors, each test being fol- lowed by a thorough cleaning and disinfecting of the premises. The tuberculin tests must be interpreted very rigidly and all questionable reactions treated as if they were positive ; otherwise the procedure will often fail to stop the headway of the disease until so many animals have been changed by repeated tests and additions that the majority of the animals have been substituted. In badly infected herds one should proceed as if every animal were infected. In herds having over 50 per cent of reactors all of the mature cattle should be treated as if infected. The tuberculin test is of value in indicating that a severe infection exists, but not of value in such herds as a means of dividing the non-infected from the tuber- culous. To control the disease dependence must be placed upon the following procedure : 1. Eliminate promptly all animals developing physical signs of the disease. 2. Remove all calves at birth and raise them on boiled or pasteur- ized milk. 18 3. Keep all healthy young stock isolated from the infected herd, infected fields and water. Test them every six months by the intra- dermal method and remove any reactors. 5 Calves are so seldom born tuberculous that such means of trans- mission may be ignored ; hence, if all calves were kept free from the disease it would require only one generation of cattle to eradicate tuberculosis. In carrying this principle into effect the ideal way would be to build up a separate herd from the healthy young stock. This, however, is not always practicable. When it is necessary to add the healthy young stock to the infected herd all of the cattle should be given careful and frequent physical examinations by a veterinarian to eliminate the open cases as far as possible. This pro- cedure of protecting the calves and young stock and of keeping down the proportion of open cases by frequent physical examinations is called Ostertag's System, named after its chief advocate, Dr. Robert Ostertag of Berlin, Germany. This system is a process of gradually weeding out and reducing the disease rather than a process of com- plete eradication. THE IMPORTANCE OF SEGREGATION AND ISOLATION In large herds it is advisable to keep the cattle in small units. In constructing buildings and corrals, plan at the least to have separate corrals for each group of fifty or sixty cattle. Provide separate water troughs for each corral. Train the cows to stand always in the same stanchion. Do not feed the calves with the sweepings from the feed troughs in the dairy barn and do not permit hogs or goats in the cattle corrals. SUGGESTIONS REGARDING SANITATION Construct water troughs so that the drinking water of the cattle does not become contaminated with manure. Do not allow the cattle access to ponds or water holes. Have plenty of windows to admit an abundance of sunlight to all buildings. Direct sunlight is more deadly to fully exposed tubercle bacilli than carbolic acid, cresol, corrosive sublimate or chloride of lime in the dilutions generally used in dis- infecting. One would suppose that tight barns would be unnecessary in Cali- fornia, where the cows can live out of doors for a greater length of time than in the eastern states, but it must be admitted that the climate s Even when the non-reacting cattle are at once removed from a herd having over 50 per cent reactors they should be looked upon as suspicious until some time has elapsed and they have successfully passed repeated tuberculin tests. The repeated use of the ophthalmic test is useful in such cases. 19 of the coast counties requires warm shelter for high-grade dairy cows. Ventilation is a sanitary factor which in some instances has been neg- lected. This should be provided not only in milking stables but also in the barns used exclusively for shelter and feeding. HOW CLEANLINESS HELPS The desirability of cleanliness in milking, cooling and transporting milk is realized by all. Few, however, realize the significance of cleanliness is a factor influencing the health of the cattle. Since the manure of tuberculous cattle often contains living tubercle bacilli in vast numbers, the importance of keeping it well cleaned out of the stable and corrals is readily seen. Stables should be cleaned out regularly and the manure put where it cannot be picked over by hogs or cattle. These animals are easily infected in that way. Cleanliness also includes keeping the walls and ceilings free from dirt, dust and cobwebs. These are all good resting places for disease germs. Whitewashing the interior of the stable at least twice a year is a great aid to cleanliness and also has a distinct effect in destrojdng disease germs, especially when applied after thorough cleaning. In many municipalities dairy stables are required to be whitewashed at regular intervals. This should be a universal practice. STATION PUBLICATIONS AVAILABLE FOE DISTRIBUTION REPORTS 1897. Resistant Vines, their Selection, Adaptation, and Grafting. Appendix to Viticultural Report for 1896. 1902. Report of the Agricultural Experiment Station for 1898-1901. 1903. Report of the Agricultural Experiment Station for 1901-03. 1904. Twenty-second Report of the Agricultural Experiment Station for 1903-04. 1914. Report of the College of Agriculture and the Agricultural Experiment Station, July, 1913-June, 1914. 1915. Report of the College of Agriculture and the Agricultural Experiment Station, Julv, 1914-June, 1915. No. 168. 169. 178. 184. 185. 195. 207. 208. 212. 213. 216. 225. 227. 230. 234. 241. 242. 246. 248. 249. 250. Observations on Some Vine Diseases in Sonoma County. Tolerance of the Sugar Beet for Alkali. Mosquito Control. Report of the Plant Pathologist to July 1, 1906. Report of Progress in Cereal Investi- gations. The California Grape Root-worm. The Control of the Argentine Ant. The Late Blight of Celery. California White Wheats. The Principles of Wine-making. A Progress Report Upon Soil and Cli- matic Factors Influencing the Com- position of Wheat. Tolerance of Eucalyptus for Alkali. Grape Vinegar. Enological Investigations. Red Sniders and Mites of Citrus Trees. Vine Pruning in California, Part I. Humus in California Soils. Vine Pruning in California, Part II. The Economic Value of Pacific Coast Kelps. Stock-Poisoning Plants of California. The Loquat. BULLETINS No. 251. 252. 253. 254. 255. 256. 257. 261. 262. 263. 265. 266. 267. 268. 269. 270. 271. Utilization of the Nitrogen and Organic Matter in Septic and Imhoff Tank Sludges. Deterioration of Lumber. Irrigation and Soil Conditions in the Sierra Nevada Foothills, California. The Avocado in California. The Citricola Scale. Value of Barley for Cows Fed Alfalfa. New Dosage Tables. Melaxuma of the Walnut, "Juglans regia." Citrus Diseases of Florida and Cuba Compared with Those of California. Size Grade for Ripe Olives. Cottony Rot of Lemons in California. A Spotting of Citrus Fruits Due to the Action of Oil Liberated from the Rind. Experiments with Stocks for Citrus. Growing and Grafting Olive Seedlings. Phenolic Insecticides and Fungicides. A Comparison of Annual Cropping, Biennial Cropping, and Green Ma- nures on the Yield of Wheat. Feeding Dairy Calves in California. No. 65. The California Insecticide Law. 69. The Extermination of Morning-Glory. 70. Observations on the Status of Corn Growing in California. 76. Hot Room Callusing. 82. The Common Ground Squirrels of California. 106. Directions for Using Anti-Hog Cholera Serum. 107. Spraying Walnut Trees for Blight and Aphis Control. 108. Grape Juice. 109. Communit- or Local Extension Work by the High School Agricultural De- partment. 113. Correspondence Courses in Agriculture. 114. Increasing the Duty of Water. 115. Grafting Vinifera Vineyards. 117. The Selection and Cost of a Small Pumping Plant. 118. The County Farm Bureau. 121. Some Things the Prospective Settler Should Know. 124. Alfalfa Silage for Fattening Steers. 126. Spraying for the Grape Leaf Hopper. 127. House Fumigation. 128. Insecticide Formulas. 129. The Control of Citrus Insects. 130. Cabbage Growing in California. 131. Spraying for Control of Walnut Aphis. 132. When to Vaccinate against Hog Cholera. 133. County Farm Adviser. 134. Control of Raisin Insects. CIRCULARS No. 135. Official Tests of Dairy Cows. 136. Melilotus Indica. 137. Wood Decay in Orchard Trees. 138. The Silo in California Agriculture. 139. The Generation of Hydrocyanic Acid Gas in Fumigation by Portable Ma- chines. The Practical Application of Improved Methods of Fermentation in Califor- nia Wineries during 1913 and 1914. Standard Insecticides and Fungicides versus Secret Preparations. Practical and Inexpensive Poultry Ap- pliances. Control of Grasshoppers in Imperial Valley. Oidium or Powdery Mildew of the Vine. 145. Suggestions to Poultrymen concerning Chicken Pox. 146. Jellies and Marmalades from Citrus Fruits. 147. Tomato Growing in California. 148. "Lungworms." Lawn Making in California Round Worms in Poultry. Feeding and Management of Hogs. Some Observations on the Bulk Hand- ling of Grain in California. Announcement of the California State Dairy Cow Competition, 1916-18. Irrigation Practice in Growing Small Fruits in California. 155. Bovine Tuberculosis. 140. 141. 142. 143. 144. 149. 150. 151. 152. 153. 154.