Coccidia, a single-cell protozoan, colonize and attack the lining of the dog's intestine. Primarily found in situations where dogs are kept in crowded, unhygienic conditions, symptoms of coccida infestation (or coccidiosis) include appetite and weight loss, bloody stools and diarrhea with mucus. The eggs of coccidia, which are passed in the dog's feces, are spread to new host animals when they are ingested during self-grooming. Although Coccidiosis can be fatal in puppies, mature dogs usually build up immunity to this parasite.
Diagnosis is made by successive microscopic examinations of stool samples. Treatment is usually with sulfa drugs. In order to keep infection from recurring, it is essential that hygiene standards are raised, crowding is reduced and that all dog bedding and dog food bowls are disinfected.