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Coccidia oocysts
Scientific classification
Domain: Eukaryota
Kingdom: Chromalveolata
Superphylum: Alveolata
Phylum: Apicomplexa
Class: Conoidasida
Subclass: Coccidia or Coccidiasina

Coccidia (Coccidiasina) are a subclass of microscopic, spore-forming, single-celled obligate intracellular parasites belonging to the apicomplexan class Conoidasida.[1] As obligate intracellular parasites, they must live and reproduce within an animal cell. Coccidian parasites infect the intestinal tracts of animals,[2] and are the largest group of apicomplexan protozoa.

Infection with these parasites is known as coccidiosis. It is commonly found in dogs' intestines, especially in puppies due to their immature immune systems.[3] It is also found in cats and kittens.


The class is divided into four orders which are distinguished by the presence or absence of various asexual and sexual stages:

The order Eucoccidiorida is divided into two suborders. These two groups differ in their sexual development: syzygy for Adeleorina and independent gametes for Eimeriorina.

The first suborder, Adeleorina, comprises coccidia of invertebrates and the coccidia that alternate between blood-sucking invertebrates and various vertebrates; this group includes Haemogregarina and Hepatozoon. There are seven families in this suborder.

The second suborder, Eimeriorina, comprises coccidia of a variety of coccidia many of form cysts. A number of genera, including Toxoplasma and Sarcocystis, infect vertebrates.

See also[edit]


  1. ^ S.J. Brands (Compiler) (2000). "The Taxonomicon & Systema Naturae" (Website database). Taxon: Genus Cryptosporidium. Universal Taxonomic Services, Amsterdam, The Netherlands. 
  2. ^ "Biodiversity explorer: Apicomplexa (apicomplexans, sporozoans)". Iziko Museums of Cape Town. 
  3. ^ Coccidia in Dogs

External links[edit]

  • Lillehoj, Hyun S. (October 1996). "Two Strategies for Protecting Poultry From Coccidia". Agricultural Research magazine (United States Department of Agriculture: Agricultural Research Service) (October 1996).  Describes using live-parasite vaccine versus a monoclonal antibody to block the sporozoite from invading a host's cell.