The parasites traditionally referred to as coccidia that develop in the intestines of humans—
Cystoisospora belli
,
Cyclospora cayetanensis
, and
Sarcocystis
spp.—are in the Stramenopiles, Alveolates, Rhizaria supergroup in the current taxonomic scheme used by protozoologists. Oocysts of these coccidia are found in the feces of humans, and diagnosis is based ultimately on demonstrating oocysts in human stool samples. The use of molecular methods to evaluate the phylogenetics and genetic diversity of parasites has resulted in a revision of the coccidian parasites.
In vitro
culture of intestinal coccidian parasites is most often used as a tool to study developmental biology or to identify active chemotherapeutic agents. Differentiation of the intestinal coccidia to the subspecies/strain level—genotyping—can be important for epidemiologic reasons, for example to link cases in outbreak investigations or to better understand clinical outcome differences.