Coccidia

Article By:

Becker, Elery R. Division of Life Sciences, Arizona State University, Tempe, Arizona.

Levine, Norman D. College of Veterinary Medicine, University of Illinois, Urbana, Illinois.

Last reviewed:December 2019

DOI:https://doi.org/10.1036/1097-8542.144900

A subclass of the class Telosporea. These proto­zoa are typically intracellular parasites of epithelial tissues in both vertebrates and invertebrates. The group is divided on the basis of life cycles into two orders, the Protococcida (in which there is only sexual reproduction) and the Eucoccida (in which there is both sexual and asexual reproduction). There are only a few species in Protococcida and all are parasites in marine invertebrates. There are hundreds of species in Eucoccida; these are parasites in both invertebrates and vertebrates. The Eucoccida contains three suborders: Adeleina, which occur mostly in invertebrates and in which there is usually one host for the sexual stages and a different host for the asexual stages (an example is Hepatozoon muris, found in rats and transmit­ted by mites); Haemosporina, which occur mainly in vertebrates and which have their sexual stages in invertebrates (an example is Plasmodium fal­ciparum which causes malaria in humans and is transmitted by mosquitoes); and Eimeriina, which occur mostly in vertebrates and in which the sexual and asexual stages occur in the same host (an example is Eimeria, species of which cause coccidiosis in many domestic animals and wildlife and which are transmitted by filth). The malaria parasites and coccidia are of direct importance to humans and also cause important losses in chickens, cattle, sheep and other domesticated animals. See also: Eucoccida; Protozoa; Sporozoa; Telosporea

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