ENTEROHEPATITIS 627 



A horse serum has been produced (by hyperimmunization 

 of the horse with repeated injections of live spirillse). In 

 doses of 3 to 5 c.c. per bird it has given good results. Immun- 

 ization of the flock by this method would be recommended as 

 early as possible. 



ENTEROHEPATITIS. 



Blackhead. 



Definition.— A disease peculiar to turkeys. It is occa- 

 sionally observed in other birds, particularly chickens. 



Occurrence.— Blackhead is very prevalent in various sec- 

 tions of the United States, occurring often in an enzootic 

 form destroying whole flocks, and seriously interfering with 

 the raising of turkeys in many districts. It is especially 

 fatal in young birds. 



Etiology.— It is produced by a protozoon, Amoeba melea- 

 gridis. This parasite is microscopic in size and is found in large 

 numbers in the liver, ceca and other portions of the intes- 

 tinal tract. Some authorities claim that a coccidium is the 

 cause of the disease. When coccidia are present, however, 

 the above parasite also coexists which makes it probable 

 that the amoeba rather than the coccidia cause the disease. 



Pathogenesis.— Blackhead is spread by the bowel discharges 

 of the affected birds which contain the parasites in large 

 numbers. Food and water polluted with infested fecal 

 matter are taken into the digestive tract of well birds. When 

 the amoeba reach the intestinal tract they develop rapidly, 

 producing irritation to the mucosa and ultimately lead to a 

 marked inflammation. The liver as a rule is invaded during 

 the progress of the disease showing intense hepatitis. The 

 parasites may enter the liver via the lymphatic system or 

 directly through the bile duct. Intermediate agents (other 

 birds, sparrows, pigeons, etc.) are often responsible for the 

 transmission of the disease to other flocks. 



Necropsy.— The autopsy findings are confined mostly to 

 the liver and intestines. The liver is found much enlarged 

 (often three to four times normal), the surface studded with 

 whitish or yellowish spots, which when opened show degener- 



