Bovine tuberculosis and its control

Preface

THE early belief that the bacteria of human and of bovine tuberculosis were identical and that large numbers of people became infected from diseased cattle caused bovine tuberculosis to stand out somewhat conspicuously among the affections of animals.

The sanitary significance of this affection in addition to its great economic importance have caused it to be very carefully studied in each and all of its phases. Although there is still much to be ascertained concerning it, knowledge of this disease has become quite definite in many respects. However, it is a complicated subject with many difficult questions still to be answered. These relate to the various diagnostic tests and the differentiation of its cause from closely allied species of bacteria.

The preparation of this volume was undertaken largely at the instance of practitioners of veterinary medicine and health officers who during recent years have sought for a summary of the knowledge of bovine tuberculosis and its control. It seemed that for those who are intelligently working to eradicate this scourge benefit would be derived from bringing together the results of the more important investigations on the nature, diagnosis and various methods for the control of this disease.

Individuals, commissions, government laboratory workers and state experiment stations have made many contributions to the knowledge of this subject. While it is impossible to summarize this literature, the publications listed and the citations given will, it is believed, make it possible for those interested in the subject to ascertain fully the details of the work that has been done on this disease.

I am indebted to Dr. S. H. Burnett of this laboratory and Dr. A. R. Keith for the photographs from which the illustrations were made. The original specimens are in the collection of the Department of Comparative Pathology and Bacteriology of the New York State Veterinary College.

V. A. M.

Ithaca, N. Y., January, 1913.

Appendix

Report of the International Commission on the Control of Bovine

Tuberculosis 105

ILLUSTRATIONS

I. Tubercle bacteria.

II. Cultures of tubercle bacteria.

III. Growth of tubercle bacteria on glycerin bouillon.

IV. Structure of a tubercle.

V. Temperature curves after tuberculin.

VI. Bronchial glands (Smith).

VII. Tuberculous lung.

VIII. Tubercle opening into a bronchus.

IX. Tuberculous lung, diaphragm and liver.

X. Tuberculous nodules on lung.

XI. Tuberculous pleura.

XII. A cross section of a tuberculous heart.

XIII. Tuberculous gland.

XIV. Tuberculous gland.

XV. Tuberculous glands.

XVI. Tuberculous mediastinal gland.

XVII. Enlarged tuberculous mesenteric glands.

XVIII. Tuberculous ulcers in the intestine.

XIX. Tuberculous ulcers and enlarged glands at ileo-caecal valve.

XX. Tuberculous liver.

XXI. A section of tuberculous liver.

XXII. A tuberculous omentum.

XXII I. A tuberculous omentum.

XXIV. A tuberculous omentum.

XXV. A tuberculous spleen.

XXVI. A tuberculous udder.

XXVII. Tuberculous lesions in skin.

XXVIII. A tuberculous uterus.

XXIX. A tuberculous focus in bone.

XXX. A tuberculous spleen from a pig.

REFERENCES

The following are a few of the more available publications on bovine tuberculosis. The reports of State and Government Departments of Agriculture and many boards of health as well as the veterinary and medical literature of the last twenty years contain many articles on this subject.

Curtice. The detection of tuberculosis in cattle. Annual Report, Bureau

of Animal Industry, U. S. Dept. of Agric, 1895-96. Dorset. Experiments concerning tubercvilosis. Bulletin 52, Bureau of

Animal Industry, 1904.

heitsamte, Bd. II (1884). Translated in Vol. CXV, New Sydenham

Society.

Koch. The combating of tuberculosis in the light of the experience that

has been gained in the successful combating of other infectious diseases.

Amer. Vet. Review, Vol. XXV (1901), p. 441. MoHLER. Infectiveness of milk of cows which have reacted to the tuberculin test. BuUedn 44, Bureau of Animal Industry, 1903. MOHLER. The tuberculin test of cattle for tuberculosis. Farmers' Bulletin

351, U. S. Dept. of Agric, 1909.

MoHLER AND WASHBURN. A Comparative study of tubercle bacilli from

varied sources. Bulletin 96, Bureau of Animal Industry, 1907. Moore. A report on bovine tuberculosis. N. Y. State Dept. of Agric, 1903. NocARD. The animal tuberculosis. New York. Pearson. The Pennsylvania plan for controlling tuberculosis of cattle.

Proceedings Amer. Vet. Med. Assn., 1899, p. 161. Pearson. Tuberculosis in cattle and the Pennsylvania plan of its repression.

Bulletin 75, Penn. Dept. of Agric, 1901. Pearson. The repression of tuberculosis in cattle by sanitation. Bulletin

74, Penn. Dept. of Agric, 1901.

Peterson. The elimination of tubercle bacilli from man and animals.

Thesis for Doctor of Philosophy, Cornell University. 1910. Reports of the International Congress on Tuberculosis, especially Sixth

Congress held in Washington, D. C, 1908. Report of the Royal Commission on Tuberculosis (Human and Animal).

London. 1907.

vUi REFERENCES

Report of the International Commission on the Control of Bovine Tuberculosis appointed by the American Veterinary Medical Association, 1910. Also published as Circular 175 of the Bureau of Animal Industry, U. S. Dept. of Agric, 1911. Reprinted in Appendix. Also Farmer's Bulletin No. 473, U. S. Dept. Agric, 1911.

Salmon. Legislation with reference to bovine tuberculosis. Bulletin 28, Bureau of Animal Industry, 1901.

Salmon. The tuberculin test of imported cattle. Bulletin 32, Bureau of Animal Industry, 1901.

Salmon. Tuberculosis of the food-producing animals. Bulletin 38, Bureau of Animal Industry, 1906.

SCHROEDER. Milk and its products as carriers of tuberculosis infection. Circular 143, Bureau of Animal Industry, 1909.

ScHROEDER AND CoTTON. The relation of tuberculous lesions to the mode of infection. Bulletin 93, Bureau of Animal Industry, 1906.

ScHROEDER AND COTTON. Experiments with milk artificially infected with tubercle bacilli. Bulletin 86, Bureau of Animal Industry, 1906.

SCHROEDER AND COTTON. Tubercle bacilli in butter. Circular 127, Bureau of Animal Industry, 1908.

SCHROEDER AND MOHLER. The tuberculin test of hogs. Bulletin 88, Bureau of Animal Industry, 1906.

Shumway. a hand-book on tuberculosis among cattle, 1895.

Smith. Investigations concerning bovine tuberculosis with special reference to diagnosis and prevention. (Pathological part.) Bulletin No. 7, Bureau of Animal Industry, 1894.

Ward and Baker. Experiments with the intradermal test for tuberculosis in cattle. Proceedings Am. Vet. Med. Assn., 1910.

Bulletins on Tuberculosis from the Various State Agricultural Experiment Stations

Bang. The application of tuberculin in the suppression of bovine tuberculosis. Bulletin 41. Massachusetts. 1896. (A translation.)

Beach. The history of a tuberculous herd of cows. Bulletin 24. Storrs, Conn. 1902.

Bitting. Bovine tuberculosis in Indiana. Bulletin 63. Indiana. 1896.

Brewer. Tuberculosis. Bulletin 41. Utah. 1895.

Briscoe and MacNeal. Tuberculosis of farm animals. Bulletin 149. Illinois. 1911.

Buckley, Tuberculosis of animals. Bulletin 145. Maryland. 1910.

REFERENCES ix

Cary. Bovine tuberculosis. Bulletin 67. Alabama. 1895.

Conn. The relation of bovine tuberculosis to that of man and its significance in the dairy herd. Bulletin 23. Storrs, Conn. 1902.

DiNWiDDlE. The relation of virulence for the domestic animals of human and bovine tuberculosis. Bulletin 57. Kansas. 1899.

DiNWiDDiE. The relative susceptibility of the domestic animals to the contagia of human and bovine tuberculosis. Bulletin 63. Kansas. 1900.

Fischer. Bovine tuberculosis. Bulletin 69. Kansas. 1898.

Glover. Relation of bovine to human tuberculosis. Bulletin 66. Colorado. 1901.

Grange. Tuberculosis. Bulletin 133. Michigan. 1896.

Harding, Smith and Moore. The Bang method, etc. Bulletin 277. Geneva, N. Y. 1906.

Hills and Rich. Bovine tuberculosis. Bulletin 42. Vermont. 1894.

Law. Tuberculosis in relation to animal industry and public health. Bulletin 65. (Cornell), New York. 1894.

Law. Experiments with tuberculin on non-tuberculous cows. Bulletin 81. (Cornell), New York, 1894.

Law. Tuberculosis in cattle and its control. Bulletin 150. (Cornell), New York. 1898.

Marshall. A study of normal temperatures and the tuberculin test. Bulletin 159. Michigan. 1898.

Marshall. Killing the tubercle bacilU in milk. Bulletin 173. Michigan. 1899.

Mayo. Some diseases of cattle, Texas itch, blackleg, tuberculosis, Texas fever. Bulletin 69. Kansas. 1897.

Mayo and Kerr. Treatment of bovine tuberculosis. Bulletin 199. Virginia. 1912.

Moore. Bovine tuberculosis. Bulletins 225 (1904) and 250 (1908). (Cornell), New York.

Moore. The elimination of tubercle bacteria from infected cattle, and the control of bovine tuberculosis and infected milk. Bulletin 299. (Cornell) , New York. 1911.

Nelson. On the use of Koch's lymph in the diagnosis of tuberculosis. Report of the biologist. New Jersey. 1893.

Nelson. Experimental studies of the Koch test for tuberculosis. New Jersey. 1895.

Nelson. The suppression and prevention of tuberculosis of cattle and its relation to human consumption. Bulletin 118. New Jersey. 1896.

X REFERENCES

Nesom. Tuberculosis of cattle. Bulletin 50. South Carolina. 1900.

Paige. History of tuberculosis in a college herd. Use of tuberculin in diagnosis. Bulletin 26. Massachusetts. 1894.

Pearson. Tuberculosis of cattle. Bulletin 29. Pennsylvania. 1894.

Reynolds. Bovine tuberculosis. Bulletin 51. Minnesota. 1896.

Reynolds and Beebe. Dissemination of tuberculosis by the manure of infected cattle. Bulletin 103. Minnesota.

Russell. Tuberculosis and the tuberculin test. Bulletin 40. Wisconsin. 1894.

Russell. The history of a tuberculous herd of cows. Bulletin 78. Wisconsin. 1899.

Russell. A lesson in bovine tuberculosis. Bulletin 114. Wisconsin. 1904.

Russell. Two ways of treating tuberculosis in herds. Bulletin 136. Wisconsin. 1905.

Russell. The spread of tuberculosis through factory skim milk with suggestions as to its control. Bvdletin 143. Wisconsin. 1907.

Russell and Hastings. Bovine tuberculosis in Wisconsin. Bulletin 84. Wisconsin. 1901.

Russell and Hastings. Distribution of tuberculosis in suspected and nonsuspected herds in Wisconsin. Bulletin 133. Wisconsin. 1906.

Russell and Hastings. Tuberculin test and its manner of application. Bulletin 134. Wisconsin. 1906.

Russell and Hastings. A catechism on bovine tuberculosis. Wisconsin. 1911.

Russell and Hoffmann. A 3-year campaign against bovine tuberculosis in Wisconsin. Bulletin 175. Wisconsin. 1909.

Stalker and Niles. Investigation of bovine tuberculosis with special reference to its existence in Iowa. Bulletin 108. Iowa. 1895.

Stance. Tuberculosis and its detection. Bulletin 107. Iowa. 1912.

Thorne. Bovine tuberculosis. Bulletin 108. Ohio. 1899.

Ward and Haring. Bovine tuberculosis. Bulletin 99. California. 1908.

Williamson and Emery. Tuberculosis and its prevention. Bulletin 117. North Carolina. 1895.

CHAPTER I History of Tuberculosis in Cattle

UBERCULOSIS is one of the oldest diseases of cattle of which we have identifying records. The Mosaic laws (Leviticus xxii, 22) contain rules that the flesh of animals which sufifer from "wen or scurvy" should not be used as food. The Talmud, especially the Mishnah, codified at the close of the second century, and the Gemara (fifth century) contain numerous enactments against the eating of such flesh. It is stated on good authority that "kandi" and "timari" refer to tuberculosis. It is evident that in the eleventh and twelfth centuries, tuberculosis was fairly well known to the Arabian Rabbi, Isaak ben Jacob Alfasi, an authority on the Talmud, and the French physician Rashi (1040-1105).

In the ninth century, the Franks enacted ecclesiastical laws against the eating of the flesh of cattle and swine which were affected with tuberculosis of the serous membranes. In 1370 it was forbidden in Munich to offer for sale the flesh of tuberculous animals. Similar laws were passed in 1343 in Wiirtsburg; in 1394 in Passau; in 1401 in Landshut; in 1558 in Wiirtemburg; and later similar regulations were enforced in other provinces.

In 1702 Florinus gave a description of the symptoms of the disease during life. At that time the name "French disease" was applied to it in Germany. This grew out of the belief which prevailed in certain quarters that tuberculosis was connected with or related to human syphilis. The term Franzosenkrankheit is said to have been first used by Helmont. In consequence of this theory of its origin, all tuberculous cattle had to be destroyed. Severe penalties were imposed for the violation of this sanitary law.

In 1783, the Berlin Board of Health published regulations for meat inspection in which the characteristics of the "French disease" were described; rejected the theory that tuberculosis was related to syphilis; and made the declaration that the flesh of tuberculous cattle was fit for human food. In the same year, Kersting of Hanover expressed a similar view in a report to the Government of Mecklenburg- Strelitz. Franck of Baden expressed the opinion that the consumption of the flesh of cattle which were only slightly affected with tuberculosis might be permitted. Graumann declared in 1784, in a government order of Mecklenburg- Schwerin, that such meat might be eaten. Following this declaration and perhaps in consequence of it, all the orders throughout Prussia which had been issued against the consumption of the flesh of tuberculous cattle were cancelled in 1785, and throughout Austria in 1788.

In 1816, Tscheulin laid down certain rules with regard to the inspection of meat from tuberculous cattle in which three stages or degrees in the extent of the disease of bovine tuberculosis were recognized, namely: (1) that in which only the tubercles were to be removed; (2) that in which the diseased parts were to be destroyed and the balance of the meat to be sold at a cheap price; and (3) carcasses which were declared to be entirely unfit for food owing to the extent of the disease. A similar procedure regarding meat inspection was carried out in Southern Germany, Switzerland, Austria, France, Belgium, Spain, Italy and other countries.

Consumption and bovine tuberculosis were for many years considered as two different diseases. Thus Virchow, Schiippel, and others declared that the tubercles in cattle were lymphosarcomata. Leisering regarded them as sarcomata. On the other hand, Spinola and Haubner maintained that bovine tuberculosis and human tuberculosis were identical.

Klencke* published a work in 1846 in which he accuses

HISTORY OF TUBERCULOSIS IN CATTLE 3

cow's milk of being the cause of a certain sickness in children. He maintained that there is a positive connection between the milk of scrofulous and tuberculous cows and the frequent development of scrofula (tuberculosis of the glands of the neck) in bottle-fed children. His observations seem to be the first recorded concerning the direct communicability of tuberculosis. In 1865, tuberculosis was demonstrated to be infectious. In that year, Villemin showed that it could be produced in healthy animals by inoculating them with pieces of tuberculous tissue. His results were confirmed by a number of other investigators. Thus Chauveau, in 1868, produced tuberculosis experimentally by feeding tuberculous material to cows. These experiments were confirmed by Klebs, Cohnheim and Gerlach. The last mentioned was the first to show that tuberculosis could be produced by feeding animals the flesh and milk of tuberculous cattle. As a result of these experiments, attempts were at once made to prevent the sale of the flesh of tuberculous animals. Since the previous regulations respecting the sale of tuberculous meat had already been abrogated, or were in force in but a few places, these attempts were met by the vigorous opposition of those financially interested.

There was, perhaps, a tendency at that time for hygienists to take an extreme position as to the danger of using the products of tuberculous animals. For instance, Gerlach said: "Pearl disease is not only incurable but it renders the animal completely worthless; meat and milk from such animals are never to be used as human food in a raw or imperfectly cooked condition."

It must be remembered in this connection that the early stages of tuberculosis as now recognized were then almost unknown, for a cow that was then considered to be tuberculous was in a rather advanced stage of disease. As earlier stages of the disease were recognized, the German veterinary council took a more conservative position and in 1875 rendered an opinion to the effect that experience and observation did not justify the extreme measures that were advocated by many, and the Imperial authorities were asked to furnish means for the study of the question as to whether, and to what extent, the use of the flesh and milk of tuberculous cattle could be injurious to people. The results of this further study have brought about the development of rigid systems of meat inspection. The United States stands foremost in the efficiency of this service.

In 1882, Robert Koch discovered the bacterium (bacillus) of tuberculosis and thus completed the already abundant evidence that tuberculosis was a specific, infectious disease. The finding of its specific cause led to many careful and extended investigations into its nature, the means by which it is spread, and the measures that must be adopted if its spread is to be checked.

The discovery of tuberculin by Robert Koch in 1890 marked the beginning of widespread efforts to eradicate bovine tuberculosis. The later discovery by Theobald Smith that bovine and human tubercle bacteria were not identical in their morphology, cultural characters and virulence precipitated one of the most intense scientific investigations that modern medicine has witnessed. It has been participated in by a very large number of sanitarians, bacteriologists and pathologists in many countries. The results of these numerous inquiries have given us very definite knowledge of the nature of the disease which, if properly applied, will, it is believed, enable cattle owners to eliminate tuberculosis from their herds, if it is there, and to keep it out, if it is not present.

CHAPTER II Distribution, Economic and Sanitary Importance OF Bovine Tuberculosis

At the present time, tuberculosis is a wide-spread disease among cattle. It is reported to be more or less prevalent in nearly every locality where dairying is an active industry. It is also found in range cattle where it has been introduced with breeding stock. Ward states that 10 per cent of the cattle killed in the South San Francisco stock yards that came from the open ranges were tuberculous. In those parts of the country where the dairy industry is restricted to small herds and where there has been very little exchange of cattle it is rare. On the other hand, where milk production is the chief occupation of the people and where the supply of milk is continuous throughout the year, tuberculosis among cattle is very common. Thus we find the spread of this disease greatly aided by the habits of dairymen that were adopted to meet the demands of the cities for fresh milk. Dr. Melvin, Chief of the Bureau of Animal Industry, states that it is estimated that about 10 per cent of the dairy cattle of the country are infected.

In tracing the spread of tuberculosis it is found that it was introduced into certain localities of Western Europe and into America, from which centers it spread somewhat slowly at first but gradually increased with the development of the cattle traffic. From the infected localities it extended to uninfected ones through the introduction of one or more diseased animals. The cattle of Denmark, according to Prof. Bang, became infected from those imported from Scotland. The United States and Canada introduced tuberculosis in a similar manner although it is not known from what country or at just what time it occurred.

The early history of tuberculosis in cattle in the United

States and Canada is very obscure. A careful search in the papers, magazines and published reports of Agricultural Societies and organizations as well as the veterinary literature fails to reveal evidence of the time of its first introduction into this country. In the American Farmer for 1822 (p. 152), Dr. Eli S. Davis of Abberville, S. C, concludes that the theory of the contagiousness of tuberculosis is false. The Farmer's Companion and Horticultural Gazette for 1852 mentions consumption as one of the most dangerous diseases of cattle and one which "will become mortal if not immediately attended to." The report of the Massachusetts Society of Agriculture for 1880 points out that certain cases of suspected contagious pleuro-pneumonia of cattle were cases of tuberculosis. There are very few references to tuberculosis in cattle in this country prior to 1865; indeed the agricultural and veterinary literature* contains little about this disease until after Koch had discovered its cause in 1882. Attention was centered on tuberculosis in cattle in 1890 when it was found that tuberculin caused a reaction in many animals apparently healthy but on post mortem found to contain somewhere in their bodies small or larger active tubercles.

In 1907, in order to determine the extent to which the disease had spread in certain dairy districts of New York, I collected the results of a number of tests that were made during that and previous years, but largely in 1907, by a considerable number of veterinarians to whom tuberculin had been furnished. The results showed that of 421 herds tested, 302 contained cattle that reacted. These herds contained a total of 9,633 animals, of which 3,432 reacted. The herds were distributed in 39 counties. The greater number of the tests were made for one or the other of the three following reasons, namely: (1) when the herd was suspected of being diseased; (2) when the purchasers of animals required the test before accepting the

*The Veterinarian (London) in 1830 (Vol. VI) describes the symptoms and treatment of consumption in cows.

DISTRIBUTION, ECONOMIC AND SANITARY IMPORTANCE 7

cattle; and (3) when the purchasers of the milk or its products required that the cows should be tuberculosis free.

The official tests by the State Department of Agriculture for the years 1904-6 inclusive, kindly furnished me by Dr. Kelly then acting Chief Veterinarian, include 262 herds with a total of 3,088 animals, of which 673 reacted. They were distributed in fifty counties. These herds all came under the operation of the law. Infected animals were found in 121 herds.

The reliable available data for New York State at that time were restricted to 683 herds, aggregating 12,721 animals, distributed in fifty counties. Of the 683 herds, 423 contained reacting individuals. A small percentage of the reactors gave physical evidence of being diseased. Although these figures show a somewhat extensive infection of the herds examined it must be remembered that they represented only about one-half of one per cent of the cattle of the State, and those from the sections presumably most highly infected.

The reports of tuberculin tests in other states show that in dairy districts where the herds have been built up by the indiscriminate purchase of cows the disease is quite prevalent. The number of animals that are infected can not be determined as but a small percentage of them are tested. It seems to be very clearly established that there are localities where it is much more prevalent than elsewhere. It is also clearly shown that there are many places where farmers have not bought cattle from without, at least to any appreciable degree, and that tuberculosis is rare in these localities. The fact, however, that it has been reported from nearly if not all dairy districts in the United States warrants the general assertion that it is widespread.

In considering the economic importance of tuberculosis among cattle the essential fact relative to its distribution must be kept in mind. When it is once introduced, it is liable to spread from infected to well animals with more or less rapidity.

The time necessary for a tuberculous cow to infect a large percentage of the cattle in the herd depends upon the rapidity with which the lesions in the infected animal develop to the stage where the tubercle bacteria are thrown off. There is a great difference in the length of time required for this development. In some cases the tuberculous areas become surrounded with a wall of fibrous tissue which checks the growth and the animal may never show evidence of its presence. In other animals the infection may result in the rapid spread of the disease within the body and in the course of a few weeks or months tuberculous areas may discharge into some channel of excretion and the organisms be eliminated with either the saliva, feces, uterine discharges or the milk. It is impossible, therefore, to predict when a cow that reacts to tuberculin but appears to be perfectly well physically will spread the virus. This difference in the rapidity with which the disease develops depends upon the virulence of the infecting organism and the resistance of the animal. Pathogenic bacteria such as those of tuberculosis are not always possessed of the same degree of disease producing power. The resisting power of different individuals and even of the same individual under different conditions varies. It is impossible in the natural course of infection to determine the degree or extent of either of these factors. If this phase of the disease is understood it will explain why some animals that react continue to remain apparently well, while others develop physical signs of the disease and infect many individuals in the herd within a period of a few months. While these facts pertain to the nature of the disease, they are important in this connection to explain why some herds become infected rapidly and others more slowly or not at all after the introduction of a reacting animal or animals.

Economic Importance. It is difficult to estimate the loss from bovine tuberculosis. There are many ways in which it operates financially against owners of livestock. Briefly stated, they are as follows:

DISTRIBUTION, ECONOMIC AND SANITARY IMPORTANCE 9

1. By destroying cattle outright, as when tuberculosis is allowed to reach its full development and kill its victim.

2. By reducing the market value of the animal, as in those cases in which the beast is sold before the disease has reached such a stage as to render it entirely unmarketable.

3. By reducing the breeding value of a herd and its general productivity.

4. By causing a waste of cattle food by feeding animals that can not give an adequate return.

5. By infecting other animals such as calves, swine and other cattle through the milk and by direct contact.

6. By injuring the reputation of the herd, thereby rendering it difficult to dispose of the animals or their products.

7. By destroying the enthusiasm or interest of the breeder in the maintenance of his herd at a high standard.

In reference to the first two of these points it may be said that careful statistics gathered some time ago by Siedamgrotzky in Germany show that the cattle industry of that country was taxed to the extent of 6,762,660 marks per year, as a result of condemnation of carcasses and destruction of parts of carcasses, in slaughter houses; and these figures do not begin to represent the total loss from tuberculosis in that country. Renneberger estimated that the total loss amounted to more than 90,000,000 marks annually. This was considered a conservative estimate. It is recognized that tuberculosis injures the livestock industry in Germany to a far greater extent than any other pest, and this includes such exceedingly virulent affections as rinderpest, lung plague, foot-and-mouth disease, anthrax and others.

"The slaughter-house statistics of Prussia show 14.6 per cent of the cattle and 2.14 per cent of the hogs to be tuberculous. In Saxony the percentage is 29.13 for cattle and 3.10 for hogs. In the city of Leipzig, the figures are 36.4 per cent for cattle and 2.17 per cent for hogs (Siedamgrotzky). Of 20,850 animals in Belgium tested with tuberculin in 1896, 48.88 per cent reacted (Stubbe). Of 25,439 tested in Denmark from 1893 to 1895, 49.3 per cent reacted; and of 67,263 tested from 1896 to 1898, 32.8 per cent reacted (Bang). An examination of 20,930 cattle in Great Britain, either slaughtered and examined post-mortem or tested with tuberculin, showed 5,441, or 26 per cent, affected with tuberculosis. MTadyean estimates that 30 per cent of the cows in Great Britain are tuberculous."

The amount of tuberculosis found in the food animals by the Government veterinary inspectors in this country is enormous. During the fiscal year 1905, there were inspected 6,134,388 carcasses of beef animals, of which 10,956 were condemned for this disease. The increase of tuberculosis in hogs is shown by the fact that in 1900, of 23,336,884 hogs that were inspected, 5,440 were affected sufficiently to cause a condemnation of some one or more parts of the carcass. In 1905, of 25,357,425 hogs inspected post mortem, 64,919 carcasses and 142,105 parts of carcasses were condemned for tuberculosis. I am told that last year (1911) one packing house lost $154,000 worth of hogs from this disease. It should be remembered that these condemnations were made on the inspection of hardly a third of the animals killed in the United States for human food. It is also important to note that these inspections were made on animals slaughtered in our larger packing houses and that these animals were in a better general condition than many which are slaughtered locally.

In 1908, Dr. Melvin, Chief of the Bureau of Animal Industry, made the following significant statement at the Congress on Tuberculosis in Washington. ^

"While the saving of human life affords the highest motive for combating tuberculosis, the prevention of financial loss is alone a sufficient reason for undertaking the eradication of the disease from farm animals. Statistics of the United States Federal meat inspection for the fiscal year ending June 30, 1908, covering 53,973,337 animals, or more than one-half of all those slaughtered for food in the country, show the iMelvin. Am. Vet. Review, Vol. XXXIV (1908) p. 250.

DISTRIBUTION, ECONOMIC AND SANITARY IMPORTANCE 11

following percentage of tuberculosis: Adult cattle, 0.961; calves, 0.026; hogs, 2.049; sheep and goats, 0. The proportion of tuberculosis is probably higher in animals slaughtered without inspection. Reports of tuberculin tests made in the 15 years from 1893 to 1908 by Federal, State and other officers with tuberculin prepared by the Bureau of Animal Industry have been carefully analysed and tabulated. Out of 400,000 cattle tested (mostly dairy cattle) there were 37,000 reactions, or 9.25 per cent. From these two classes of statistics it is concluded that on the average about 10 per cent of the milch cows, 1 per cent of other cattle, and 2 per cent of the hogs in the United States are affected with tuberculosis, the average percentage for all the cattle being estimated at 3.5.

"The accuracy of the tuberculin test has been confirmed in a remarkable way by post mortem examinations. Out of 23,869 reacting cattle slaughtered, lesions of tuberculosis were found in 23,585, a percentage of 98.81. Properly prepared tuberculin applied by a competent person is therefore shown to be a wonderfully reliable agent for diagnosing tuberculosis. In cases where the test appears to give unsatisfactory results, this is usually due to the use of a poor quality of tuberculin or to ignorance or carelessness in applying it.