142 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



ERADICATION OF TUBERCULOSIS FROM SWINE. 



It is generally accepted that probably 90 per cent of all tuber- 

 culosis in swine is from cattle sources. It can thus be readil}^ under- 

 stood that the ultimate control and eradication of tuberculosis in 

 swine depends upon its eradication from cattle. It is therefore 

 believed that freeing areas from bovine tuberculosis will reduce 

 to the ultimate minimum the per cent found in swine. Attention was 

 given to tracing the sources of infection in hogs which were found 

 affected with tuberculosis when slaughtered at establishments under 

 Federal meat inspection. 



INSPECTION AND TESTING FOR INTERSTATE MOVEMENT. 



\ 



The list of veterinary practitioners authorized to make tuberculin 

 tests of cattle for interstate shipment has been increased to 8,010 

 names. The work of these men has shown improvement. They 

 tested 149,548 cattle, of which 2,777, or 1,8 per cent, were reactors. 



Kegularly employed bureau inspectors tested at public stockyards 

 or at other official stations 35,485 cattle, from which there were re- 

 moved 653 reactors, or 1.8 per cent. 



In accordance with the regulation requiring that a permit be 

 issued for the interstate movement of known tuberculous cattle for 

 immediate slaughter or for return to the original owner for breeding 

 purposes, permits were issued covering 25,706 reactors" for slaughter 

 and 35 for return to owners. Such movement often makes available 

 better marketing facilities and better prices, thus lessening the 

 amount of State and Federal indemnities required. 



TUBERCULIN TESTING. 



The large number of cattle tested with tuberculin during the 

 past year (2,384,236) afforded an excellent opportunity for the 

 veterinarians to improve their knowledge of the various forms of 

 the tuberculin test and for the bureau to standardize methods 

 throughout the service. 



Statistics of tests by the various methods are as follows: Subcu- 

 taneous method, 156,365 cattle, with 7,507 reactors, or 4.8 per cent ; 

 intradermic method, 1,738,207 cattle, with 57,029 reactors, or 3.3 

 per cent; ophthalmic method, 2,814 cattle, with 116 reactors, or 4.1 

 per cent; combination tests, 445,136 cattle, with 17,605 reactors, or 4 

 per cent. The demand for area testing is largely responsible for the 

 extensive use of the intradermic method. Retests by other methods 

 following this method have confirmed its reliability. Further ex- 

 perience with the various tests shows that all are valuable and re- 

 liable when used according to circumstances. 



Bureau inspectors tested 53 per cent of the total herds tested, 

 55 per cent of the total cattle, and obtained 49.5 per cent of the 

 total reactors. 



Investigations regarding the incidence of tuberculosis in calves 

 showed that approximately 4 per cent of the calves were infected. 

 Without the use of the intradermic method of testing these animals 

 would have been permitted to remain in the herds. 



The average cost of testing by bureau inspectors, including salaries 

 and expenses of field veterinarians, but not office expenses or salaries 



