TUBERCULOSIS OF BIRDS 617 



location. When the bacilli are taken into the general circula- 

 tion specific lesions will be found in the spleen, lungs, joints, 

 etc. The large number of nodules found in the intestinal 

 wall develop in most cases from the infection following along 

 the course of the lymph nodes, or from the bacilli becoming 

 lodged between the serous and muscular coats of the bowel, 

 producing a reactive inflammation and the formation of 

 tubercles. The toxic action of the chemical products of 

 the bacilli produces a gradual emaciation, cachexia, and 

 ultimately death. 



Natural Infection. —Most cases of tuberculosis in fowls no 

 doubt result from eating foods contaminated with bowel 

 discharges from affected birds. Bacilli are found in the 

 feces of affected birds in large numbers, particularly in those 

 cases where ulcerations are present on the intestinal mucosa. 

 Another very common source of infection is when healthy 

 birds eat the organs of those that have succumbed to the 

 disease. Carelessness in disposing of dead birds makes this 

 a very common source of infection. There is a possibility 

 of birds contracting the disease from the fecal discharges of 

 cattle affected with tuberculosis. This is a disputed point 

 at the present time. There is considerable doubt also about 

 their contracting the disease from the sputum of the human 

 subject. Parrots seem to contract the disease from this 

 source. Numerous cases have been recorded where fowls 

 contracted tuberculosis, and at the same time the attendants 

 had the disease. Whether transmission of the disease is 

 brought about in this way is in dispute. Flocks are usually 

 infected from newly acquired tubercular birds. Pigeons may 

 carry the disease from flock to flock. 



Pathology.— The chief anatomical changes are found in the 

 liver, spleen, intestines, joints, and in parrots in the joints, 

 and skin about the head and neck. The surface of the liver 

 is covered with numerous small nodules and on cross-section 

 they are found to extend into or through the entire structure. 

 Sometimes the tubercles become confluent and form large 

 masses, white, gray, or grayish-white in color, the centers of 

 which are caseous. The liver is frequently much enlarged, 

 very friable indicating fatty degeneration. The spleen is 



