THE PROTOZOAN SUBGROUPS 325 



Infectious Entero-Hepatitis of Turkeys 



This disease — commonly known as blackhead — has been attributed 

 to an organism found by Theobald Smith in the necrotic liver of affected 

 turkeys and named by him Ameba meleagridis. That this is an ameba, 

 however, has been questioned. Certain other investigators consider 

 the organism described by Smith as a form in the development of in- 

 testinal Coccidia, the acceptance of which conclusion would place the 

 disease among the coccidioses. 



The term "blackhead" has been used to designate a number of dis- 

 eases of fowls, among which, in addition to entero-hepatitis, are 

 cholera, helminthiasis, intestinal coccidiosis, and, in general, any dis- 

 ease which may be accompanied by dark discoloration of the comb and 

 wattles. 



Symptoms. — It has been shown that entero-hepatitis can be trans- 

 mitted directly from diseased to healthy turkeys, natural infection prob- 

 ably taking place through food and water contaminated with the 

 droppings from the affected animals. At the expiration of the incuba- 

 tion period, which is usually within one month, the disease is initiated 

 by loss of appetite and a drooping listlessness which is soon followed 

 by diarrhea, the fluid discharge being yellowish in color and of exceed- 

 ingly offensive odor. Weakness and emaciation have already set in, 

 and the comb and wattles show the blackish discoloration from which 

 the disease takes its name, — blackhead. 



Death usually occurs after a course of from five to eight days. The 

 mortahty is highest in young animals, among which it is estimated to 

 be eighty to ninety per cent. Adults are more likely to recover, though 

 usually only after a long period of emaciation during which there may 

 be a relapse. 



Post-mortem Appearance. — The changes observed on necropsy are 

 those of necrotic degeneration of the cecal mucosa and liver. The walls 

 of the ceca are thickened, the mucous membrane ulcerated and covered 

 with fibrous membranes and exfoliating necrotic tissue. The liver is 

 much enlarged and shows on its surface numerous yellowish areas with 

 the centers softened. These areas may be quite small or up to 15 mm. 

 (5/8 of an inch) or more in diameter. Other portions of the digestive 

 tract are not affected. 



Examination in hanging drop of emulsified tissue of the cecal mucosa 

 and the necrotic foci of the liver will reveal the amebse. The organisms 

 found in the liver occur as rounded or oval cells measuring 6-14 microns 

 and having a comparatively small nucleus. Smith concluded from his 

 investigations that the parasites were not intracellular but lived in the 

 tissue spaces. In the liver they are thought to occupy the spaces of the 

 necrosed and disappearing liver cells. 



