David R. Shlim, Barbara L. Herwaldt

Infectious Agent

Cyclosporiasis is caused by Cyclospora cayetanensis, which is a protozoan (unicellular), coccidian parasite; oocysts (rather than cysts) are shed in the feces of infected persons.

Mode of Transmission

• Infection results from ingestion of mature (infective) Cyclospora oocysts, such as in contaminated food or water.
• Direct person-to-person transmission is unlikely because the oocysts shed in feces must mature in the environment (outside the host) to become infective to someone else. Limited data indicate that the maturation process requires from days to weeks in favorable conditions.

Occurrence

• Cyclosporiasis appears to be most common in tropical and subtropical regions of the world.
• Outbreaks in the United States and Canada have been linked to various types of imported, fresh produce.

Risk for Travelers

• Persons of all ages are at risk for infection.
• Travelers to developing countries can be at increased risk.
• In some regions where cyclosporiasis has been studied, the risk for infection is seasonal. However, no consistent pattern has been discerned with respect to time of year or environmental conditions.

Clinical Presentation

• Cyclospora infects the small intestine. Asymptomatic infection has been documented, particularly in settings where cyclosporiasis is endemic.
• Among symptomatic persons, the incubation period averages 1 week (range 2 days to ≥2 weeks).
• Onset of symptoms is often abrupt but can be gradual; some persons have a flu-like prodrome.
• The most common symptom is watery diarrhea, which can be profuse.
• Other common symptoms include anorexia, weight loss, abdominal cramps, bloating, nausea, and body aches. Vomiting and low-grade fever may be noted.
• If untreated, the illness can last for several weeks or months, with a remitting–relapsing course and prolonged fatigue and malaise.

Diagnosis

• Infection is diagnosed by detecting Cyclospora oocysts (8–10 μm in diameter) in stool specimens.
• Stool examinations for ova and parasites usually do not include methods for detecting Cyclospora unless clinicians specifically request testing for this parasite.
• Cyclospora oocysts commonly are shed at low levels, even by persons with profuse diarrhea. This constraint underscores the utility of repeated stool examinations, sensitive recovery methods (particularly concentration procedures), and detection methods that highlight the organism: Cyclospora oocysts autofluoresce when viewed by UV fluorescence microscopy and can be stained with modified acid-fast or modified (“hot”) safranin techniques.
• For more information about these and other laboratory methods, visit CDC’s Division of Parasitic Diseases’ DPDx website: www.dpd.cdc.gov/dpdx/HTML/Cyclosporiasis.htm. Diagnostic assistance is available through DPDx (www.dpd.cdc.gov/dpdx/).

Treatment

• The treatment of choice is trimethoprim–sulfamethoxazole (TMP-SMX). The typical regimen for immunocompetent adults is TMP, 160 mg, plus SMX, 800 mg (one double-strength tablet) orally, twice a day for 7–10 days.
• No highly effective alternatives have been identified for persons allergic to (or intolerant of) TMP-SMX. Clinicians may consult CDC about possible approaches for such persons (CDC Public Inquiries, 770-488-7775; parasites@cdc.gov).
• Additional information about clinical issues can be found on the Division of Parasitic Diseases’ website at www.cdc.gov/ncidod/dpd/parasites/cyclospora/default.htm.

Preventive Measures for Travelers

• No vaccine is available.
• Travelers to developing countries should be advised to follow the precautions described in the Water Disinfection for Travelers in Chapter 2.
• Disinfection with chlorine or iodine is unlikely to be effective against Cyclospora oocysts.

References

1. Herwaldt BL. Cyclospora cayetanensis: a review, focusing on the outbreaks of cyclosporiasis in the 1990s. Clin Infect Dis. 2000;31(4):1040–57.
2. Shlim DR. Cyclospora cayetanensis. Clin Lab Med. 2002;22(4):927–36.