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[Cyclospora cayetanensis]

Oocyst of Cyclospora cayetanensis in unstained wet mounts of stool. Image taken at 1000x magnification.

Oocyst of Cyclospora cayetanensis in an unstained wet mount of stool. Image taken at 1000x magnification.

Oocyst of C. cayetanensis stained with safranin (SAF).

Oocysts of C. cayetanensis stained with safranin (SAF).

Oocyst of C. cayetanensis viewed under UV microscopy.

Autofluorescence of an oocyst of Cyclospora under UV microscopy.

Causal Agents

Cyclospora cayetanensis, a coccidian protozoan. It appears that all human cases are caused by this species.

  1. Herwaldt BL. Cyclospora cayetanensis: a review, focusing on the outbreaks of cyclosporiasis in the 1990s. Clin Infect Dis 2000;31:1040-1057.
  2. Ortega YR, Gilman RH, Sterling CR. A new coccidian parasite (Apicomplexa: Eimeriidae) from humans. J Parasitol 1994;80:625-629.
  3. Pieniazek NJ, Herwaldt BL. Reevaluating the molecular taxonomy: Is human-associated Cyclospora a mammalian Eimeria species? Emerg Infect Dis 1997;3:381-383.

Life Cycle

Life cycle of cyclosporiasis

When freshly passed in stools, the oocyst is not infective The number 1. (thus, direct fecal-oral transmission cannot occur; this differentiates Cyclospora from another important coccidian parasite, Cryptosporidium). In the environment The number 2., sporulation occurs after days or weeks at temperatures between 22°C to 32°C, resulting in division of the sporont into two sporocysts, each containing two elongate sporozoites The number 3.. Fresh produce and water can serve as vehicles for transmission The number 4. and the sporulated oocysts are ingested (in contaminated food or water) The number 5.. The oocysts excyst in the gastrointestinal tract, freeing the sporozoites which invade the epithelial cells of the small intestine The number 6.. Inside the cells they undergo asexual multiplication and sexual development to mature into oocysts, which will be shed in stools The number 7.. The potential mechanisms of contamination of food and water are still under investigation.

Geographic Distribution

Cyclosporiasis has been reported in many countries, but is most common in tropical and subtropical areas. Since 1990, at least 11 foodborne outbreaks of cyclosporiasis, affecting approximately 3600 persons, have been documented in the United States and Canada.

Clinical Presentation

After an average incubation period of 1 week, symptomatic infections typically manifest as watery diarrhea, which can be severe. Other symptoms include anorexia, weight loss, abdominal pain, nausea and vomiting, myalgias, low-grade fever, and fatigue. Untreated infections typically last for 10-12 weeks and may follow a relapsing course. Infections, especially in disease-endemic settings can be asymptomatic.

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  • Page last reviewed March 31, 2016
  • Page last updated April 1, 2016
  • Content source: Global Health - Division of Parasitic Diseases and Malaria
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