118 Diseases of Poultry 



the difference between the avian and the other two types is. 

 much greater than that between the human and the bovine. 



It has frequently been held that the avian bacillus is a 

 distinct species. The chief reason for this is that it often 

 fails to produce disease when inoculated into mammals 

 and because the mammahan type will not always infect birds. 

 At the present time the view is rather generally accepted 

 that the avian, human and bovine types simply represent 

 three varieties or strains of the same species. A large amount 

 of work has been done upon this subject, and while under 

 ordinary conditions the avian bacillus does not infect mam- 

 mals, under certain conditions it will do so. 



Bang,^ who has done a great amount of work upon this 

 subject, found that mammalian bacilli by passage through 

 fowls can be so changed as to behave like the avian type, and 

 further that bovine bacilli after having lost their virulence 

 for guinea pigs through repeated passage through fowls are 

 able to regain the original virulence by passage through 

 mammals. Of eighteen different strains of mammalian 

 tubercle bacilli used Bang found that twelve could be made 

 virulent for fowls. He states, however, that in his experi- 

 ence mammalian bacilli were never found in spontaneous 

 avian tuberculosis. 



The avian tubercle bacilli are very virulent to most birds 

 and especially to domesticated species. Artificial infection 

 succeeds best by direct inoculation into a vein, while in- 

 traperitoneal and subcutaneous injections are apt to yield 

 less certain results. By feeding either cultures or fresh 

 material from tuberculous birds the disease is readily trans- 



' Bang, Oluf, "Die Tuberculose der Gefliigels in ihren Bezie- 

 hungen zur Tuberculose der Saugethieren." Trans. IX Intern., Vet. 

 Cong., Vol. 1, 1909. 



"Gefliigeltuberculoseund Saugetiertuberculose." Cenlralb. 



f. Bakt. Paras, u. Infekl., Bd. XLVI, 1908. 



