220 SWINE DISEASES 



in the liver or pancreas may also be eliminated in the 

 feces. 



Tubercle bacilli from open tubercular lesions of the 

 urogenital organs are eliminated in the urine, seminal 

 fluid, or other discharges from these organs. Infection is 

 directly eliminated from open, cutaneous, tuberculous 

 lesions, and tubercle bacilli may be eliminated in the 

 milk, especially if tuberculous lesions exist in the mammary 

 gland. 



The dissemination of tubercle bacilli in the body and 

 the possibility of their elimination through any channel 

 is facilitated by leukocytes. Thus tubercle bacilli in the 

 lung may be incorporated and retained by leukocytes 

 that are later eliminated by the mammary cells, and the 

 milk become infected even though the mammary gland 

 contain no tuberculous lesions. 



From the foregoing it is evident that any of the dis- 

 charges of tuberculous animals may contain the tubercle 

 bacilli. In the United States and in practically all other 

 countries tuberculosis of cattle is prevalent, particularly 

 among cattle used for dairy purposes. 



The most frequent source of porcine tuberculosis is 

 from tuberculous cattle. Swine become infected from 

 infected cow's milk, feces, nasal discharges, and the car- 

 casses of tuberculous cattle that are given them for food 

 A limited number of swine become infected from garbage 

 that contains the human tubercle bacilli. This has been 

 especially observed in swine fed upon garbage from tuber- 

 culosis sanitaria, or hotels. An occasional case of uterine, 

 ovarian, or testicular tuberculosis is the result of direct 

 infection by copulation. It is possible that infection 

 may be transmitted in the exhaled air from infected to 

 healthy swine. 



Channels of entrance. The most frequent channel 

 of entrance of the tubercle bacilli in swine is the digestive 

 tube, the infection being introduced in food or water. 

 An occasional case may become infected by the inhalation 

 of the bacilli and by direct transmission through the geni- 

 tal organs. Mammary tuberculosis may be the result 



