DISEASES OF ANIMALS 



115 



noted, it may be taken for granted that 

 the animal is tuberculous. The great 

 value of tuberculin, therefore, lies in 

 the fact that it enables us to recognize 

 tuberculosis in animals before any ex- 

 ternal symptoms appear. 



One of the surprising facts in con- 

 nection with tuberculosis is that an ani- 

 mal may be affected for a year or two 

 without losing weight and without 

 showing any visible signs of the disease. 

 During this time, however, it may spread 

 tuberculosis throughout the herd. 



Eradication of the disease — The sys- 

 tem recommended by Bang, of Den- 

 mark, for the eradication of tuberculo- 

 sis, consists in applying the tuberculin 

 test to all cattle in the herd, separating 

 those which react from those which do 

 not react and preventing the two herds 

 from subsequently coming in contact. 

 The milk of reacting cows is sterilized 

 before using as food for calves or man. 

 In this way tuberculous cows may be 

 used for breeding purposes for a num- 

 ber of years and the loss to the farmer 

 is much less than would be the case if 

 he slaughtered all reacting eattle at 

 once. 



In localities where the percentage of 

 tuberculosis is high, Ostertag recom- 

 mends modification of this system, ac- 

 cording to which the reacting and non- 

 reacting animals are not separated, since 

 this involves so much extra work. The 

 tuberculin test is applied frequently and 

 the milk of all reacting cows is steril- 

 ized before being used. In this way 

 the calves are prevented from becoming 

 infected. 



During the past five or six years, de 

 Schweinitz, Von Behring, Pearson, 

 Arloing and others have worked out a 

 system of preventive vaccination against 

 tuberculosis. This scheme consists in 

 using tubercle bacilli of low virulence, 

 preferably obtained from man, for the 

 purpose of inoculating young, healthy 

 calves. As a result of this inocula- 

 tion a mild form of the disease is pro- 

 duced; the calves may cough for a few 

 weeks and show some loss of flesh ; later 

 they recover and are thereafter immune 

 to tuberculosis. This method has al- 

 ready been tried on more than 10,000 

 young cattle, with quite satisfactory re- 

 sults, and appears to be gaining ground 

 wherever it has been tried. 



Sanitation a preventive — Cattle kept 

 under sanitary conditions are less 



liable to become infected than those 

 which are maintained almost continu- 

 ally in filthy barns without proper light 

 or ventilation. Under range conditions, 

 where cattle are outdoors nearly all of 

 the time, tuberculosis is almost un- 

 known. In herds kept under unsatis- 

 factory conditions, however, the disease 

 may affect from 50 to 95 per cent of the 

 herd. The extent of infection in the 

 United States cannot be stated with any 

 certainty but probably ranges from 20 

 to 30 per cent, while in Europe it is 

 considerably higher 



Milk is UNWHOLEfOME — With regard 

 to the milk of tuberculous cows, it has 

 been shown beyond question that, in a 

 majority of cases, the milk does not 

 contain tubercle bacilli. They may be 

 present, however, at any moment and 

 such milk cannot, therefore, be con- 

 sidered as safe under any conditions ex- 

 cept after sterilization or some other 

 treatment. Recently Von Behring has 

 recommended that the milk of tubercu- 

 lous cows be treated with formalin to 

 the extent of 1 part in 20,000 to 

 40,000 parts. It is argued that in this 

 way the tubercle bacilli arc killed with- 

 out destroying the vaccinating property 

 of such milk. It may be possible that 

 the continued use of tuberculous milk 

 treated with formalin may ultimately 

 produce some immunity in man. 



Contagious pleuro-pneumonia [ s a 

 specific disease affecting cattle, but nut 

 other^ animals, and is characterized by 

 an inflammation of the lungs and 

 pleura, leading to death in the vast ma- 

 jority of cases and spreading rapidly 

 among all exposed cattle. Fortunately, 

 this disease does not exist at present in 

 the United States, and it is hoped that 

 it will never occur again. At one time 

 it prevailed extensively, but it was erad- 

 icated by the efforts of the Bureau of 

 Animal Industry, and no case has been 

 known in the United States since 1S92. 



Rinderpest, also known as cattle 

 plague, is an infectious disease attack- 

 ing chiefly the digestive organs. It is 

 not known in the United States, but has 

 prevailed to an alarming extent in the 

 Philippines. The micro-organism of 

 this disease has not been isolated, but 

 the virus may be transmitted from one 

 animal to another, either directly or 

 indirectly. The symptoms are high 

 fever, repeated chills, rapid pulse, great 

 debility, drooping of the ears, rapid fall- 



