TUBERCULOSIS OF BIRDS 619 



In some cases small nodules are found beneath the skin on 

 various parts of the body. Parrots are affected in the major- 

 ity of cases locally around the eyes, face, or on the neck, or 

 the articulations may be involved. The lesions are small, 

 round, or oval nodules developing on some part of the skin 

 or mucous membrane. Later they become caseous. Their 

 characteristics vary somewhat, depending upon whether they 

 are located in the skin, or in the mucous membrane of the 

 mouth. The nodules when irritated often become quite 

 large, rupture, and leave an extensive ulcerous surface. When 

 the joints are involved the same symptoms are observed as in 

 fowls. General symptoms occur occasionally in parrots. 



Diagnosis. — The diagnosis from the symptoms presents 

 considerable difficulty. However, when we consider that a 

 number of fowls in a flock are affected with a disease causing 

 emaciation, exhaustion and death, we should suspect tuber- 

 culosis. Several methods of diagnosis have been recom- 

 mended of which the following have given the best results: 

 (a) An affected bird is killed and an autopsy made. The 

 tubercular lesions are quite characteristic and the tubercle 

 bacilli may be found under the microscope. (6) By use of 

 avian tuberculin. This method has been employed quite 

 extensively of late. It has been found quite reliable in most 

 cases. The tuberculin is injected, using about 0.003 per 

 bird, into the deeper layers of the skin of the comb or wattles, 

 using a small dental syringe. Care should be observed that 

 the needle is not inserted too deeply, or the tuberculin will 

 enter the subcutaneous tissues. On the other hand, it must 

 not be too superficial or the epithelial layer will rupture and 

 allow the tuberculin to escape. The reaction consists in a 

 rounded swelling which develops in twenty-four to seventy- 

 two hours at the point of injection. The degree of reaction 

 varies with individual cases. 



Differential Diagnosis.— There are several conditions which 

 might be confused with avian tuberculosis, viz: (a) Asthenia 

 (" going light") which is characterized by gradual emaciation, 

 and exhaustion, but negative findings on autopsy. Micro- 

 scopic examination will aid in revealing the difference, (b) 

 External parasites when affecting a number of birds in a 



