Coccidial infections in birds

Coccidian parasites are protozoans in the subphylum Apicomplexa, class Sporozoa, which have a characteristic apical complex of organelles in the infective stages that enable the parasites to enter host cells. These intracellular organisms cause a myriad of diseases in avian species by destroying the cells they invade. For the clinician, some of these parasites can present an antemortem diagnostic challenge owing to the variety of bird species and organ systems affected; therefore, instituting an effective treatment regimen can be an additional hurdle. This article reviews the following coccidian parasites of nondomestic avian species: Eimeria, Isospora, Caryospora, Cryptosporidium, Atoxoplasma, Sarcocystis, and Toxoplasma. Life cycles, clinical signs, diagnostic tests, prevention, and treatment are discussed.