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Cyclospora cayetanensis is a coccidian parasite that causes acute and chronic diarrhea in both immunocompetent and immunocompromised hosts. Cyclospora is phylogenetically related to other coccidian parasites, including Cryptosporidium, Isospora, Toxoplasma, and Sarcocystis. Initially described as cyanobacteria-like (blue-green algae) bodies in the stools of patients with prolonged diarrhea, anorexia, and fatigue,1Cyclospora species are now known to be ubiquitous, infecting a variety of animals, including reptiles, insectivores, and rodents. However, Cyclospora cayetanensis is the only species that is known to infect humans.2,3 Although the organism has been recovered in the stool of affected individuals from numerous regions—including North America, Central America, South America, Caribbean Islands, eastern Europe, South Africa, Southeast Asia, India, Nepal, Peru, and Haiti—infection appears to be most common in tropical and subtropical countries.4

Cyclosporiasis in developed countries is associated with international travel and waterborne or food-borne outbreaks. For example, Cyclospora has caused a waterborne outbreak among house staff in Chicago5 and is a leading cause of persistent diarrhea among travelers to Nepal in spring and summer.6 In the United States and Canada, infections have been linked to imported fresh produce such as raspberries, blackberries, basil, and baby lettuce leaves.7 Guatemalan raspberries have been associated with about 50 outbreaks from 1995 to 2000.7,8 More recently, fresh snow peas from Guatemala were associated with an outbreak of cyclosporiasis in a residential facility in Pennsylvania.9 The use of untreated or poorly treated water for irrigating crops, applying fertilizers, and washing and processing foods has been implicated as a source of contamination for fruits and vegetables.10 Cyclosporiasis associated with recreational exposure to water, especially swimming pools, has also been reported.11,12

The oocysts of C. cayetanensis are spherical, about 8 to 10 μm in size and surrounded by a thick wall.10 They are smaller than Isospora belli and twice the size of Cryptosporidiumparvum. Infection is initiated by the ingestion of the sporulated oocysts. During excystation, sporozoites are released and undergo asexual (merogony and schizogony) and sexual reproduction (gametogony) within the gastrointestinal epithelium.13 Oocysts are unsporulated, and are thus noninfectious, when freshly passed in the stool. Sporulation occurs in the environment in about 1 to 2 weeks. The oocysts can persist in food, in water, and in the environment. Washing fruits and vegetables may not be sufficient to remove the oocysts.14

Clinical Manifestations

C. cayetanensis infects both immunocompetent and immunocompromised hosts. The incubation period is estimated to be 1 to 14 days, with an average of 7 days.7 Infection with Cyclospora may be asymptomatic, may manifest as mild to moderate self-limiting diarrhea (usually in the healthy host), or may be protracted and severe. In the immunocompetent host, the mean duration of diarrheal symptoms ranges from 10 to 25 days in outbreak settings.7,15 In endemic infections and international travelers, mean duration of symptoms seems ...

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