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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
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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
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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
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Clinical Manifestations
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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 to ...