A coccidian parasite that affects mammals, fish, and poultry; abbreviated taxonomy: Eukaryota; Alveolata; Apiocomplexa; Coccidia; Eimeriida; Eimeriidae. Sporozoites that invasde intestinal mucosa cause diarrhea, hemorrhage, tenesmus, dehydroation, weight loss, and in advanced states, emaciation. Sheep, goats, poultry, cattle, and rabbits are most affected clinically. There are four sporocysts per sporulated oocyst, two sporozoites per sporocyst. Pathogenic species include E. bovis, E. zuernii in cattle, E. ovina in sheep, E. tenella, E. necatrix, E. acervulina, and E. brunetti in poultry. Eimeria sp. are not parasitic for dogs or cats. E. sardinae of herring and tuna was previously thought to be a human parasite but is found in human feces only as a result of having eaten infected fish. Not all Eimeria sp. are pathogenic; pathogenic strains vary in their pathogenicity.