TUBERCULOSIS 293 



The bacilli are eliminated in the excreta, and infection is 

 by way of the alimentary tract. The disease is spread from 

 flock to flock by the sale of tuberenlar birds, and possibly 

 by the sale of eggs, which, when the ovaries are tubercular, 

 may contain the organisms. The chicks hatched from the 

 may develop the disease, a case of hereditary trans- 

 mission. 



Tuberculosis can be detected with some degree of cer- 

 tainty by inject in.ir a small amount of tuberculin prepared 

 by the use of the avian tubercle bacillus. It is preferable 

 to avoid the purchase of stock from suspected flocks, and to 

 get rid of the entire flock when the disease has made its ap- 

 pearance, rather than to attempt to eradicate it in other 

 ways. 



There is no reason to believe the disease is of sanitary 

 importance. It may have other economic aspects than those 

 mentioned, for it has been shown that the organism is 

 capable of producing a non-progressive form of the disease 

 in hogs which may cause the rejection of certain parts by 

 the meat inspectors. To avoid such trouble and to prevent 

 the spread of the disease in the flock, all dead birds should 

 be buried, so that they can not be eaten by hogs or birds. 



Differential diagnosis. There are a number of diseases 

 that may be mistaken for tuberculosis in domestic animals. 

 Actinomycosis may produce nodules in the udder that re- 

 semble tubercular nodules. Sheep are sometimes affected 

 by an intestinal disease known as nodular disease, which to 

 the uninitiated might be thought to be tuberculosis, but is 

 really caused by a parasitic worm which burrows into the 

 wall of the intestine, forming a greenish-colored nodule 

 about the size of a pea. 



Johne's disease. As has been mentioned, there are a 

 number of acid-fast bacilli other than the tubercle bacillus. 

 The disease, known as Johne's disease, is becoming of con- 



