212 AVIAN TUBERCULOSIS 



O. Columbianum Curtice. In chickens a nodular taeniasis of 

 the intestine is not infrequently mistaken for tuberculosis. 

 Abscesses and necrotic foci due to various agencies must also 

 be distinguished from tuberculous lesions. Enlargement of the 

 lymphatic glands may be due to Hodgkin's disease. 



In cases of actinomycosis, the ray fungus can usually be 

 detected on a microscopic examination. Bacterium mallei can 

 be found either in cultures or by guinea pig inoculations in 

 cases of glanders, and in parasitic diseases the specific animal 

 parasite can be found if diligently sought. A careful study of 

 the recent lesions, especially in the nodules caused by the 

 animal parasites, will show that they are not structurally like 

 the tubercle as described above. 



From the symptoms and morbid anatomy it is clear that 

 hard and fast lines for diagnosing tuberculosis cannot be laid 

 down. As a rule the lesions are characteristic, although there 

 are many exceptions. In making a positive diagnosis one 

 must rely upon the discovery microscopically of the .specific 

 bacterium, the result of animal inoculation or the effect of 

 tuberculin. 



The tubercle bacteria can be tound by making and prop- 

 erly staining cover- glass preparations from the tuberculous 

 tissues or discharges in a certain number of cases. When 

 these tuberculous lesions open into the respiratory tract the 

 specific bacteria can almost always be found in the expectora- 

 tion. This is especially true in men, and Ravenel and others 

 have .shown that it is often true in cattle. In old and in the 

 very recent tuberculous lesions, it is not so easy to detect these 

 organisms microscopically. When there is doubt animal inoc- 

 ulation gives quite prompt results. 



Tuberculosis in fowls is to be differentiated from certain 

 other affections, such as lymphadenoma and sarcoma of the 

 liver, asthenia, nodular taeniasis and excessive infestion w^ith 

 the air sac mite {Cytodites nudiis). Because of a close simi- 

 larity in the general symptoms, and, in certain cases, of the 

 gross lesions, between tuberculosis and certain other affections, 

 the findings of a .somewhat careful examination are necessary 



