UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION CIRCULAR No. 264 May, 1923 PRELIMINARY ESSENTIALS TO BOVINE TUBERCULOSIS CONTROL IN CALIFORNIA By GEOEGE H. HAET Non-reacting yearling heifers, the offspring of tuberculous sires and dams in the herd shown on page 7. Kept free from tuberculosis by removal at birth to a separate ranch and raised on properly pasteurized milk. INTEODUCTION During the past few years the state of California has rapidly advanced to national prominence in the dairy industry field. In this state many of those factors essential to progressive dairying, such as the elimination of the scrub bull, development of cow testing associa- tions, dairy sanitation, advanced registry work, and improved quality of dairy products, are being developed along constructive lines on a large scale. These progressive measures bring into strong contrast the indifference which often exists in regard to the health of the dairy animals, an indifference which is prevalent despite the obvious fact that no single factor in progressive dairying is more fundamental than the health of the herds that make the foundation upon which the entire industry rests. Z UNIVERSITY OF CALIFORNIA EXPERIMENT STATION For many years California was obliged to import dairy cattle. ' This was necessary for the development of our herds to their present number, size, and quality in the comparatively short period of time in which it has been accomplished. High producing pure-bred and grade cattle have been shipped in from the thickly populated dairy centers in the Middle West and the Atlantic Coast. It is well known to all persons who have studied the history and distribution of tuber- culosis that such areas are the most heavily infected with this disease. At the time this importation was taking place, animals that gave a negative reaction to the tuberculin test were commonly accepted without any investigation as to the history of tuberculosis in the herds from which they originated. Although the importance of considering the tuberculin test history of the herd rather than of the individual cow was recognized at the time, and had been clearly set forth by the International Commission of the American Veterinary Medical Asso- ciation on the Control of Bovine Tuberculosis, it had not been given specific attention. Even today it is still far from being given universal consideration in the purchase of tuberculosis-free cattle. The disease was, therefore, brought into the state in many cases with the foundation stock that started a certain number of our pure- bred herds. In a few instances, in animals kept under the most approved conditions, tuberculosis was found to be present so soon after their arrival that there could be no question that it had been brought in with them. On account of the long distance they had been shipped, their cost per head upon arrival, the difficulty of getting financial redress from the original owners, and the need for high-producing dairy animals of proper blood lines in the state, the owners became indifferent to the importance and seriousness of the disease, and affected animals were allowed to remain in the breeding herds. This was particularly unfortunate because from these herds pn re-bred sires, and often foundation females, went out to the grade herds. The question of tuberculosis or the tuberculin test was not raised at sales within the state for years. The spread of the disease was greatly augmented by transferring cattle in small groups from farm to farm by means of the public auction. Many herds of badly diseased cattle were thus distributed throughout the state. Since 1915, when the state pure milk law was passed requiring tuberculin testing of cows whose milk was to be consumed in the raw state, the demand for tuberculin tested cattle has been gradually increased. To meet this demand it has been the practice to purchase Circular 264] BOVINE TUBERCULOSIS CONTROL IN CALIFORNIA 3 animals subject to the test. However, the seller has frequently kept the reactors in his own herd or sold them later to a buyer not demand- ing a tuberculin test certificate. Years of such practices are now having their effect. Tuberculosis is a chronic and slowly progressing disease in a great many of the individual animals attacked. T have known cows to remain profitable dairy animals for eight years after they first reacted to the tuberculin test. It is not a disease that devastates the herd in a short time. The losses it causes, though very large in the aggregate, extend over so long a period of time that they are not acutely felt. Despite the presence of this disease, therefore, our dairy herds have increased in number and size until we are now in a position to become a dairy cattle exporting state. The demand for export cattle is present in Mexico, the Rocky Mountain states, particularly Nevada, and the islands and countries on the Pacific, and this demand will undoubtedly increase. We have the cattle and their dairy quality is satisfactory, but they do not possess the necessary health qualifications. In several instances animals exported from this state have not satisfactorily passed tuberculin tests upon arrival at their destinations. Today the elimination of affected animals from interstate and foreign shipment is looked after very carefully by purchasers as well as livestock sanitary authorities. Even though California is the logical source of supply for export animals to the above-mentioned points, there is no possibility of this market being maintained unless our cattle can meet the health requirements. At the same time, the local demand for tuberculosis free cattle is greater than the supply, which condition is forcing purchases of such animals from outside the state and further interfering with the home market. The accredited herd and tuberculosis-free area work being carried out on a large scale by the Federal Bureau of Animal Industry in cooperation with all of the states, has developed a large number ot tuberculosis-free herds in the United States. This work has been started recently in this state. Many of our livestock owners are getting a correct idea of the situation and want to take action, while others, who undoubtedly recognize the facts, want to postpone action as long as possible in order that their present activities in the sale and movement of cattle may not be restricted. The well-informed already realize, and the majority of our dairy cattle owners must appreciate the fact, that there are very important preliminary essentials to be considered in a matter of this kind. 4 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION Much discussion has ensued regarding the value of the tuberculin test, which of the three tests is preferable, how the reading of the test shall be made, whether animals once reacting and later failing to do so should be considered healthy, and many other points, to the entire exclusion of the following essential considerations: THE DEVELOPMENT OF A SOURCE OF SUPPLY OF FEMALES OF EQUAL QUALITY TO REPLACE THE REACTING ANIMALS This is one of the most difficult problems that presents itself in a widespread campaign for controlling tuberculosis. Many owners of livestock would be willing to have the tuberculin test applied and stand the loss in disposing of the reacting animals, provided they could purchase healthy animals to take their places. Many years ago it was found impossible to purchase cattle free from tuberculosis for the certified dairies around San Francisco Bay on the tuberculin test alone. The Medical Milk Commissions of San Francisco and Alameda counties, therefore, adopted in 1909 what has been termed the ' ' 10 per cent rule" for all purchases. This consists in having all the animals in a herd from which purchases are to be made tested with tuberculin, and in case more than 10 per cent react the entire herd is to be rejected. The purchase of cattle under these restrictions became so difficult on account of the prevalence of the disease that all of the certified dairies are now keeping up the numerical strength of their herds to a large extent by raising young stock on their own premises. At the present time, many carloads of grade cattle are being shipped into the Los Angeles district annually from the Middle West because the San Joaquin Valley and other points in the state from which these animals should be supplied cannot meet the health test. While tuberculosis-free cattle can be supplied from outside the state, the distance of shipping, time required for acclimation, and the cost are prohibitive to a considerable percentage of our dairy herd owners. The tuberculosis-free area work carried on in remote places, such as Lassen and Modoc counties and in Round Valley in Mendocino County, is being undertaken because in these places there are small numbers of dairy animals many of which are native stock and have not, therefore, become heavily infected with this disease. Such areas at the present time, although comparatively free from tuberculosis, furnish no source of supply of healthy females. It is possible, how- ever, for females to be raised in these areas even though they have to be shipped from the dairy districts as weaned calves and regularly tuberculin tested. In time such free areas may devote their attention CIRCULAR 264] BOVINE TUBERCULOSIS CONTROL IN CALIFORNIA 5 to the raising of dairy rather than beef animals because greater financial returns will be obtained thereby. Livestock men should seriously consider this phase of the tuberculosis problem and cooperate to solve it. THE IMPORTANCE OF HERD TUBERCULIN TESTS RATHER THAN TESTS UPON INDIVIDUAL ANIMALS It is essential for livestock men to understand at the outset that the tuberculin test is not 100 per cent efficient. The test furnishes, however, an entirely satisfactory means of controlling tuberculosis if Fig. 1. — This cow, apparently in perfect health, was found to be tuberculous on application of the tuberculin test. its limitations are recognized and proper consideration given them. A single animal that gives a negative tuberculin test may or may not be tuberculous, but a herd of animals kept together for a reasonable period of time all giving a negative tuberculin test may safely be considered free from the disease. In herds where there are certain percentages of reactors we can expect to get rid of the disease by removing the reactors, subject to certain conditions. Except in special cases, all the animals in herds that are running from 35 per cent to 50 per cent or more reactors should be considered diseased. In general the larger the herd of animals, the lower must be the percentage of reactors if the herd is ever to become entirely free from the disease. 6 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION For example, in a small herd of twenty cows, five or six may react and by removing these animals the disease may be eliminated from the herd with one or more subsequent tests. In case, however, there were two hundred animals and the same percentage of reactors was found, the opportunity for eradicating the disease from that herd would be much more difficult; and were the herd to consist of a thousand animals the difficulties would become many times greater. The reason for this is that the larger the herd, the greater the number of tuber- culous animals present, even though the percentage is no greater than in smaller herds. The more animals actually affected with the disease in a herd, the greater the opportunity for one or more to fail to react to the test. These non-reactors are, therefore, left in the herd and continue to spread the infection through discharges from their bodies. For this reason it is less costly to take out several animals that may show no lesions on postmortem examination than to leave one affected animal in the herd. Although it is difficult for the livestock man to accept the fact that whole herds of cattle may be tuberculous and that the control of the disease should be started from this basis in certain herds, the sooner it is recognized the more certainly will time and money be saved and endless discouragement avoided. The decision in matters of this kind will require careful thought and consideration by the owner and the advising veterinarian. BRANDING OF EEACTING ANIMALS At the present time a great many owners of livestock, who believe that they are ready for the tuberculosis eradication campaign to progress rapidly in this state, are considerably taken aback when it is stated that they must allow all reacting animals to be branded with the letter "T." This is an absolutely essential procedure for the control of the disease and must be rigidly enforced upon all veter- inarians who apply tuberculin tests, whether official or private. Under the present system that exists in this state, it is not uncommon for persons to buy cattle and have them tested by their own veterinarians. Only the non-reactors are taken. A short time after, another purchaser may appear with his veterinarian and test the herd, again taking the non-re ictors. Nothing is done with the reactors and no method of identification is placed upon them. It is a well known fact that an animal which once reacts to the tuberculin test may not react to one or more subsequent tests, and particularly is this the case when subse- quent tests are applied in rapid succession. Therefore, under such conditions all of the animals may be sold as non-reactors, although CIRCULAR 264] BOVINE TUBERCULOSIS CONTROL IN CALIFORNIA 7 they may have reacted to several tests previous to the one on which they were purchased when they did not react. Such a procedure carried out generally will make it impossible for any conscientious private veterinarian to do any tuberculin testing, because he will be confronted with conditions entirely beyond his control which com- pletely vitiate the value of his work, but for which he will receive the responsibility and condemnation. Where tuberculous animals are properly branded and segregated they may under special conditions remain profitable cows for a period of years during which time they can annually produce healthy off- spring of the quality that is desired to keep production at its normal Fig. 2. — This herd of cattle gave 67 per cent positive reactions to the tuberculin test. The entire herd was, therefore, considered tuberculous. level during the eradicaton work. A test and slaughter campaign in this state carried out too rapidly would materally reduce produc- tion and interfere with the prosperity of the dairy industry. Where segregation is attempted it must be thorough and complete, with separate land and buildings. Only a small percentage of dairy cattle owners are equipped to carry out such a plan and in general they are those having large herds and acreage and particularly those having two or more ranches. CONTEOL OF TUBEECULIN The control of tuberculin is also of great importance as a pre- liminary essential for controlling tuberculosis. Under present con- ditions anyone can purchase tuberculin and frequently one has to go no farther than the town drugstore to get a supply. Large quantities 8 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION of it axe being used by persons who are entirely unqualified to administer it but who intend to use it honestly to the best of their ability. Other persons are using it with fraudulent intentions. I recently visited a dairy ranch operated by a progressive dairy- man. He was having his herd regularly tested by an official veter- inarian under the state pure milk law on account of his product being sold as raw milk. He told me that he always kept a supply of tuberculin on hand and whenever a cow looked out of condition he tested her himself. Such indiscriminate testing is of no value and only tends to reduce the efficiency of the testing done by the official veterinarian. In many of the states of the Union, including those where the tuber- culosis campaign is progressing most satisfactorily, tuberculin is under the absolute control of the State Livestock Sanitary authorities. All shipments of this material into the state and all sales of same by laboratories within the state must be recorded with the State Veter- inarian. In case reports of the use of tuberculin are not received or there is a question as to the honesty or ability of the persons using the material, that fact is at once investigated by the authorities. This gives opportunity for the control of this material so that fraudulent practice is carried on, if at all, with great difficulty. "We believe that the testing by livestock owners of their own and their neighbors' herds of cattle must be stopped through control of tuberculin. These tests are not recognized by purchasers of the animals and from the results that have been obtained both in this and in other states it is plainly evident to the thinking man that such practice will never be successful in controlling this infection of live- stock. As long as it is allowed to continue, control of reactors is impossible. A majority sentiment of our livestock men must be developed to back morally and legally any movement to- bring about- the complete suppression of this type of work. With these primary necessities properly understood and statutes developed to render their application possible, we are then ready to proceed wth tuberculosis eradication work on a reasonable scale. Many of the lesser points, such as the handling of cattle at fairs, the proper disinfection of railway cars and stockyards, the question of indemnity and disposal of reacting cattle through slaughter houses to the best financial advantage of the owner, and so forth, are matters which will develop as the work progresses.