142 ANNUAL REPORT OF THE Off. Doc. 



The jciprr liclow is olleied lific bfcaiise it j^ivcs a review of tlie 

 work (lone uiKh'r the ansi)ices of the Stale Live Stock Sanitarv Board 

 on the vaccination of cattle against tubercnlosis. It was read before 

 the Pathological Society of Phihidelphia, November 13, 1902. 



SOME EXPEKIMENTS UPON THE IMMUNIZATION OF CATTLE 



AGAINST TUBERCULOSIS. 



BY LEONARD PEARSON, B. S. V. M. D., Staff Veterinarian of Pennsylvania, 



AST) 

 S. H. GILLILAND, V. M. D., Assistant Baiteri<i}<}0st nf the State Live Stock Sanitary Board. 



(From the Laboratory of the State Live Stock Sanitary Board of Pennsylvania.) 



When an extensively tubercular herd is tested with tuberculin one 

 usually finds some animals that do not react to the test and are free 

 from disease. These uninfected aninmls may be young or they 

 may be recent additions to the herd, and their freedom from disease 

 may be due merely to the fact that they have not had time to cootract 

 it; on the other hand, they are often cows that have been members 

 of the herd and exposed to infection for years. That the freedom 

 of these cattle that have long resisted the disease is not due to breed 

 or family immunity has, in numerous instances, been shown by the 

 fact that their parents or oli'spring have succumbed to tuberculosis. 



To what is such resistance to tuberculosis due? It is evident that 

 it does not depend upon species, breed, or lack of exposure. It is an 

 individual factor. An animal may possess some power within itself 

 to resist the tubercle bacilli that it is constantly exposed to and must 

 daily inhale and ingest. 



Careful observation of these cattle and study of them in series 

 show^ that the immunity they possess is not due to what is roughly 

 termed good geoeral health or what the stockman knows as good 

 condition. Cattle resistant to tuberculosis may suffer with some 

 other disease or be in a bad state of nutrition. Cattle that contract 

 tuberculosis show, in very many instances, until the infection is well 

 advanced, the usual signs of good health, such as soft coat, pliable 

 skin, clear eyes, good appetite, and regular growth or increase of 



