Eimeria tenella is a species of Eimeria

Eimeria

Eimeria is a genus of Apicomplexan parasites that includes various species responsible for the poultry disease coccidiosis. The genus is named for the German zoologist Theodor Eimer...

that causes hemorrhagic cecal

Cecum

The cecum or caecum is a pouch, connecting the ileum with the ascending colon of the large intestine. It is separated from the ileum by the ileocecal valve or Bauhin's valve, and is considered to be the beginning of the large intestine. It is also separated from the colon by the cecocolic...

 coccidiosis in young poultry

Poultry

Poultry are domesticated birds kept by humans for the purpose of producing eggs, meat, and/or feathers. These most typically are members of the superorder Galloanserae , especially the order Galliformes and the family Anatidae , commonly known as "waterfowl"...

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This species has a monoxeous life cycle with the definitive (only) host as chickens; it is extremely host-specific. Acquired via fecal contamination of food and water (oral-fecal route), it undergoes endogenous merogony in the crypts of Lieberkuhr (intestinal ceca of chicken) and gametogony in epithelial cells of the small intestines. Fusion of microgamete and macrogamete forms results in unsporulated zygotes, which are released with feces of chicken. The zygote sporulates after one to five days, and becomes infective.

Diagnosis is based on finding oocysts in feces. While no effective treatment exists, the rate of infection can be reduced via prophylates, anticoccidial drugs and vaccination of baby chicks.