CHAPTER IV. 

 CHRONIC INFECTIOUS DISEASES. 

 TUBERCULOSIS OF BIRDS. 



Tuberculosis Avium. Avian Tuberculosis. 



Definition.— A chronic infectious disease of chickens, ducks, 

 pigeons, parrots and canaries. It is characterized by a slow, 

 progressive emaciation, which ends in death from exhaustion. 



Occurrence. —Avian tuberculosis is a very common disease 

 of chickens and parrots. Occurring enzootically among the 

 former, enormous losses to the poultrymen result. During 

 the past few years it has made its appearance in practically 

 all sections of the United States. In a number of instances 

 entire flocks of birds have succumbed to the disease, or 

 become so infected and emaciated that their destruction 

 was necessary. The economic importance of the disease is 

 not entirely confined to those that die from the disease 

 directly, but it has an important bearing on the egg produc- 

 tion. 



Etiology.— This disease is produced by the Bacillus tuber- 

 culosis avium. Its biological characteristics are similar in 

 many respects to the Bacillus tuberculosis of other animals 

 (mammalian tuberculosis). 



Pathogenesis.— The bacilli, picked up with the food, are 

 passed directly to the intestinal tract, where they pass 

 through the lymph follicles into the intestinal wall, either 

 to become localized at this point, or to pass into the portal 

 vein and liver. Or they may gain access to the general circu- 

 lation and through it become distributed to various parts 

 of the body. It is possible that the intestines may not 

 become affected by the bacilli passing through the walls, but 

 in a great many cases tubercular nodules are found in this 



