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Causal Agent:

The causal agent has been only recently identified as a single-celled coccidian parasite. The species designation Cyclospora cayetanensis was given in 1994 to Peruvian isolates of human-associated Cyclospora. It appears that all human cases are caused by this species.

Life Cycle:

Some of elements of this figure were created based on an illustration by Ortega et al. Cyclospora cayetanensis. In: Advances in Parasitology: opportunistic protozoa in humans. San Diego: Academic Press; 1998. p. 399-418.

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.