The Eucoccidiorida are an order of microscopic, spore-forming, single-celled parasites belonging to the

apicomplexa The Apicomplexa (also called Apicomplexia) are a large phylum of parasitic alveolates. Most of them possess a unique form of organelle that comprises a type of non-photosynthetic plastid called an apicoplast, and an apical complex structure. T ...

n class

Conoidasida Conoidasida is a class of parasitic alveolates in the phylum Apicomplexa. The class was defined in 1988 by Levine and contains two subclasses – the coccidia and the gregarines. All members of this class have a complete, hollow, truncated c ...

. Protozoans of this order include parasites of humans, and both domesticated and wild animals including birds. Among these parasites are the ''

Toxoplasma gondii ''Toxoplasma gondii'' () is an obligate intracellular parasitic protozoan (specifically an apicomplexan) that causes toxoplasmosis. Found worldwide, ''T. gondii'' is capable of infecting virtually all warm-blooded animals, but felids, such as d ...

'' that cause

toxoplasmosis Toxoplasmosis is a parasitic disease caused by '' Toxoplasma gondii'', an apicomplexan. Infections with toxoplasmosis are associated with a variety of neuropsychiatric and behavioral conditions. Occasionally, people may have a few weeks or mont ...

and ''

Isospora belli ''Cystoisospora belli'', previously known as ''Isospora belli'', is a parasite that causes an intestinal disease known as cystoisosporiasis.Centers For Disease Control: https://www.cdc.gov/parasites/cystoisospora/index.html This protozoan parasit ...

'', which results in

isosporiasis Isosporiasis, also known as cystoisosporiasis, is a human intestinal disease caused by the parasite ''Cystoisospora belli'' (previously known as ''Isospora belli''). It is found worldwide, especially in tropical and subtropical areas. Infection of ...

Definition

This is the largest order in the class Conoidasida and contains those species that all undergo

merogony Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism i ...

(asexual),

gametogony Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism i ...

(sexual) and

sporogony Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism i ...

(spore formation) during their lifecycles.

Genera

Nineteen families, three subfamilies, and 70 genera are recognised in this order. The genera include: '' Adelea'', '' Adelina'', ''

Aggregata ''Aggregata'' is a genus of parasitic alveolates belonging to the phylum Apicomplexa. Taxonomy The organism found in the octopus was first named as ''Benedenia octopiana'' by Schneider in 1875. Since ''Benedenia'' was preoccupied, ''Eucoccidium' ...

'', '' Alveocystis'', ''

Atoxoplasma ''Atoxoplasma'' is a genus of parasitic alveolates in the phylum Apicomplexa. The species in this genus infect birds. They are spread by the orofaecal route. History This genus was created by Garnham in 1950. The history of this genus has been ...

'', ''

Babesiosoma ''Babesiosoma'' is a genus of parasitic alveolates in the phylum Apicomplexia. They have two hosts in their life cycle: the vertebrate hosts are fish and the invertebrate vectors are leeches. This genus has been poorly studied and little is k ...

'', '' Barrouxia'', '' Bartazoon'', '' Besnoitia'', ''

Calyptospora ''Calyptospora'' is a genus of parasitic protozoa in the phylum Apicomplexa. This genus and family was created in 1984 for the species ''Eimeria funduli'' because of morphological differences in the sporocyst suggested that it was not a typical ...

'', '' Caryospora'', '' Caryotropha'', '' Chagasella'', ''

Choleoeimeria ''Choleoeimeria'' is a genus of alveolate parasites that infect the biliary tracts of reptiles. Morphologically they are similar to the ''Eimeria'', to whom they are closely related. The genus was described in 1989 by Paperna and Landsberg. Gen ...

'', ''

Cryptosporidium ''Cryptosporidium'', sometimes informally called crypto, is a genus of apicomplexan parasitic alveolates that can cause a respiratory and gastrointestinal illness (cryptosporidiosis) that primarily involves watery diarrhea (intestinal cryptosp ...

'', '' Crystallospora'', ''

Cyclospora ''Cyclospora'' is a genus of apicomplexan parasites. It includes the species ''Cyclospora cayetanensis'', the causative agent of cyclosporiasis. Members of ''Cyclospora'' are characterized as having oocysts with two Apicomplexan life cycle, spor ...

'', '' Cyrilia'', ''

Cystoisospora ''Cystoisospora'' is a genus of parasitic alveolates belonging to the phylum Apicomplexa. Taxonomy This genus was originally created by J. K. Frenkel in 1977. Its use was discontinued but was resurrected in 2005. This genus currently includes sp ...

'', '' Dactylosoma'', '' Desseria'', '' Diaspora'', ''

Dorisa ''Dorisa'' is a genus of parasitic alveolates in the phylum Apicomplexa. The genus was separated from the genus '' Dorisiella'' by Levine in 1908.Levine ND (1980) ''Dorisa'' n. gen. (Protozoa, Apicomplexa, Eimeriidae). J Parasitol 66(1):11 ''Dor ...

'', '' Dorisiella'', ''

Eimeria ''Eimeria'' is a genus of apicomplexan parasites that includes various species capable of causing the disease coccidiosis in animals such as cattle, poultry and smaller ruminants including sheep and goats. ''Eimeria'' species are considered to be ...

'', '' Elleipsisoma'', ''

Epieimeria ''Epieimeria'' is a genus of parasitic alveaolates of the phylum Apicomplexa. The genus was created in 1981 by Dyková and Lom. Species in this genus were earlier classified as ''Eimeria''. Taxonomy Species in this genus infect fish. Descript ...

'', ''

Frenkelia ''Frenkelia'' is a genus of parasites in the phylum Apicomplexa. The species in this genus infect the gastrointestinal tracts of birds of prey (definitive hosts) and the tissues of small rodents (intermediate hosts). Taxonomy Species of this ...

'', '' Ganapatiella'', '' Gibbsia'', ''

Goussia ''Goussia'' is a taxonomic genus, first described in 1896 by Labbé, containing parasitic protists which largely target fish and amphibians as their hosts. Members of this genus are homoxenous and often reside in the gastrointestinal tract of the ...

'', ''

Gousseffia ''Gousseffia'' is a genus of parasitic alveolates belonging to the phylum Apicomplexa. This genus was originally named '' Yakimovella'' after the parasitologist Yakimoff.Levine ND, Ivens V (1979) The coccidia (Protozoa, Apicomplexa) of insectivo ...

'', '' Grasseella'', ''

Hammondia ''Hammondia'' is a genus of parasitic alveolates in the phylum Apicomplexa. History This genus was created in 1975. Before this date the species of this genus were confused with '' Toxoplasma gondii'' to which they are closely related. The ca ...

'', '' Haemogregarina'', '' Hemolivia'', ''

Hepatozoon ''Hepatozoon'' is a genus of Apicomplexa alveolates which incorporates over 300 species obligate intraerythrocytic parasites. Species have been described from all groups of tetrapod vertebrates, as well as a wide range of haematophagous arthropod ...

'', '' Heydornia'', '' Hoarella'', ''

Hyaloklossia ''Hyaloklossia'' is a genus of parasitic alveolates in the phylum Apicomplexa. Only one species in this genus is currently recognised - ''Hyaloklossia lieberkuehni''. History This parasites of this genus was first observed by Lieberkuhn in 185 ...

'', ''

Isospora ''Isospora'' is a genus of internal parasites in the subclass Coccidia. It is responsible for the condition isosporiasis, which causes acute, non-bloody diarrhoea in immunocompromised individuals. Taxonomy At least 248 species were originall ...

'', '' Ithania'', '' Karyolysus'', '' Klossia'', '' Klossiella'', '' Lankesterella'', '' Legerella'', ''

Margolisiella ''Margolisiella'' is a genus of parasitic alveolates belonging to the phylum Apicomplexa. History This genus was created in 1997 by Desser and Bower for a group of protozoa that infect little neck clams (''Protothaca staminea'').Desser SS, Bowe ...

'', '' Mantonella'', '' Merocystis'', ''

Nephroisospora ''Nephroisospora'' is a genus of parasites that infects bats History This genus was described in 2010 by Wünschmann ''et al''. Taxonomy There is one recognised species in this genus — ''Nephroisospora eptesici''. Description This genus ...

'', '' Neospora'', '' Octosporella'', '' Orcheobius'', '' Ovivora'', '' Pfeifferinella'', '' Polysporella'', ''

Pseudoklossia ''Pseudoklossia'' is a genus in the phylum Apicomplexa. Species in this genus infect marine molluscs, although one species (''Pseudoklossia microcosmi'') infects in an ascidian worm. The life cycle is heteroxenous (requires at least two hosts) ...

'', '' Pythonella'', '' Rasajeyna'', ''

Sarcocystis ''Sarcocystis'' is a genus of protozoan parasites, with many species infecting mammals, reptiles and birds. Its name is dervived from Greek ''sarx'' = flesh and ''kystis'' = bladder. The lifecycle of a typical member of this genus involves two ...

'', '' Schellackia'', ''

Selenococcidium ''Selenococcidium'' is a genus of parasitic alveolates in the phylum Apicomplexa. There is one recognised species in this genus – ''Selenococcidium intermedium''. This species infects the intestinal tract of European lobsters (''Homarus gammar ...

'', '' Selysina'', '' Sivatoshella'', '' Skrjabinella'', '' Spirocystis'', ''

Toxoplasma ''Toxoplasma gondii'' () is an obligate intracellular parasitic protozoan (specifically an apicomplexan) that causes toxoplasmosis. Found worldwide, ''T. gondii'' is capable of infecting virtually all warm-blooded animals, but felids, such as d ...

'', '' Tyzzeria'', '' Wenyonella'' Among the

heteroxenous Heteroxeny, or heteroxenous development, characterizes a parasite whose development involves several host species. Heteroxeny has been used as the basis for splitting genera. When there are two or three hosts, the development cycle is named d ...

and

cyst A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubble) ...

-forming genera are: ''Besnoitia'', ''Cystoisospora'', ''Frenkelia'', ''Hammondia'', ''Neospora'', ''Sarcocystis'', and ''Toxoplasma''.

Taxonomy

The taxonomy of this group is complex and only partly understood. Two major clades have been identified: the isosporoid coccidia (''Toxoplasma'', ''Neospora'', ''Isospora''

n part N, or n, is the fourteenth letter in the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''en'' (pronounced ), plural ''ens''. History ...

and ''Sarcocystis'') and a second clade containing ''Lankesterella'', ''Caryospora'' and the eimeriid coccidia (''Cyclospora'', ''Isospora''

and ''Eimeria''). ''Isospora'' is more closely related to the ''Toxoplasma''/''Neospora'' clade than to ''Sarcocystis''.

Families

About 1,000 species are in the genus ''Eimeria''. Some of the genera have been organised into families. *Family '' Barrouxiidae'' **Genera ***''Barrouxia'' ***''Goussia'' *Family

Sarcocystidae The Sarcocystidae are a family of Apicomplexa associated with a variety of diseases in humans and other animals. Taxonomy Genera in this family include: * ''Besnoitia'' * '' Cystoisospora'' * '' Frenkelia'' * '' Nephroisospora'' * ''Neospora'' ...

**Genera ***''Besnoitia'' ***''Cystoisospora'' ***''Neospora'' ***''Sarcocystis'' ***''Toxoplasma''

References

External links

Taxon: Order Eucoccidiorida Léger & Duboscq, 1910
, The Taxonomicon. {{Taxonbar, from=Q3734141 Apicomplexa orders