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Scientific classification
Domain: Eukaryota
(unranked): SAR
(unranked): Alveolata
Phylum: Apicomplexa
Class: Conoidasida
Subclass: Coccidiasina
Order: Eucoccidiorida
Suborder: Eimeriorina
Family: Sarcocystidae
Genus: Cystoisospora

Cystoisospora belli
Cystoisospora canis
Cystoisospora felis
Cystoisospora ohioensis
Cystoisospora orlovi
Cystoisospora rivolta
Cystoisospora suis
Cystoisospora timoni

Cystoisospora is a genus of parasitic alveolates belonging to the phylum Apicomplexa.


This genus was originally created by Frenkel in 1977. Its use was discontinued but was resurrected in 2005 by Barta et al.[1] This genus is currently used to group species that have tetrasporozoic, diplosporocystic oocysts without Stieda bodies in their sporocysts. These species infect the entrocytes of mammals and are transmitted by the orofaecal route.

DNA analysis has shown that this genus belongs to the family Sarcocystidae.[2]

The type species of this genus is Cystoisospora felis.Wenyon 1923

Life cycle[edit]

This parasite has been isolated from dogs, cats and raccoons. C. belli has been isolated from immunosuppressed humans — particularly those with HIV infection.

These parasites normally infect the entrocytes of the small intestine and are spread by the orofaecal route. The definitive hosts are cats but other species including various species of rodents may be infected. No further development occurs in these paratenic hosts and the parastites remain dormant until ingested by a definitive host.


This genus has been recorded worldwide.[3] C. felis and C. rivolta occur in up to 40% of cats in some tropical countries.[4]


Clinical signs include watery diarrhea, vomiting, fever and weight loss. The diagnosis is made by microscopic examination of the stool. Distinguishing between the species of Cystoisospora is most easily done with PCR. This method can also be used to make the diagnosis.

Treatment is based on trimethoprim-sulfonamides with clindamycin or toltrazuril for resistant strains.[5]


Hygiene on the premises is important in prevention. Good litter tray hygiene is also critical in multi-cat households. Utensils, runs, cages and other implements should be steam-cleaned or washed in boiling water. Because of the importance of paratenic hosts such as cockroaches, insect control is critical.


  1. ^ Barta JR, Schrenzel MD, Carreno R, Rideout BA (2005) The genus Atoxoplasma (Garnham 1950) as a junior objective synonym of the genus Isospora (Schneider 1881) species infecting birds and resurrection of Cystoisospora (Frenkel 1977) as the correct genus for Isospora species infecting mammals. J Parasitol 91(3):726-727
  2. ^ Samarasinghe B et al (2008) Phylogenetic analysis of Cystoisospora species at the rRNA ITS1 locus and development of a PCR-RFLP assay. Exp Parasitol 118(4) 592–595
  3. ^ Schuster RK et al (2009) The parasite fauna of stray domestic cats (Felis catus) in Dubai, United Arab Emirates. Parasitol Res 105(1): 125–134
  4. ^ Coelho WM et al (2009) Occurrence of gastrointestinal parasites in fecal samples of cats in Andradina City, São Paulo. Rev Bras Parasitol Vet 18(2), 46–49
  5. ^ Lloyd S (2001) Activity of toltrazuril and diclazuril against Isospora species in kittens and puppies. Vet Rec 148:509