Description

Cyclosporiasis is a gastrointestinal illness caused by the protozoan parasite Cyclospora cayetanensis (1,2). Direct, person-to-person (fecal-oral) transmission is highly unlikely because the parasite is not immediately infectious when it is shed in the stool of infected persons. The parasite must mature (develop) in the environment (outside the host) to become infective. Under favorable laboratory conditions, the maturation process typically requires at least 1 week. Ingestion of the parasite (e.g., in contaminated food) before it has fully matured poses no risk.

Occurrence

Infection can be acquired worldwide by ingestion of water or food contaminated with the parasite. Outbreaks in North America have been linked to various types of imported fresh produce (1).

Risk for Travelers

Persons of all ages are at risk for infection. Travelers to developing countries can be at increased risk, and the magnitude of the risk can vary by season. However, the relevant season is different in different settings and regions, and the pronounced seasonality of infection remains unexplained (1); for example, in Nepal, risk of infection is greater in the summer and the rainy season.

Clinical Presentation

Cyclospora infects the small intestine. The parasite and host factors that influence the manifestations and severity of infection are poorly understood. The incubation period typically is about 1 week (1). The symptoms can include watery diarrhea, loss of appetite, bloating, increased gas, stomach cramps, nausea, vomiting, muscle aches, and low-grade fever. Some persons first notice influenza-like symptoms. If untreated, the illness can last for weeks to months, and the symp-toms can come and go. Substantial weight loss and prolonged fatigue are commonly noted. Identification of this parasite in stool requires special laboratory tests that are not routinely done (e.g., a modified acid fast-stained specimen); specimens submitted for testing for ova and parasites usually are not examined for Cyclospora unless specifically requested (1).

Prevention

No vaccine is available. Travelers to resource-poor countries should be advised to follow the precautions in the Risks from Food and Drink section in Chapter 2. Persons with a history of Cyclospora infection should be informed that symptomatic reinfection can occur (1).

Treatment

The treatment of choice is trimethoprim-sulfamethoxazole (1, 3). The fact that therapy for cyclosporiasis differs from therapies for amebiasis, giardiasis, cryptosporidiosis, and some bacterial infections underscores the importance of diagnosing infection in returned travelers rather than treating empirically. Physicians may consult CDC about patients who are allergic to or intolerant of sulfa-containing medications. For more information, see the Division of Parasitic Diseases website at http://www.cdc.gov/ncidod/dpd/parasites/cyclospora/factsht_cyclospora.htm and http://www.cdc.gov/ncidod/dpd/parasites/cyclospora/healthcare_cyclospora.htm.

References

1. Herwaldt BL. Cyclospora cayetanensis: a review, focusing on the outbreaks of cyclosporiasis in the 1990s. Clin Infect Dis. 2000;31:1040-57.
2. Ortega YR, Sterling CR, Gilman RH, Cama VA, Diaz F. Cyclospora species: a new protozoan pathogen of humans. N Engl J Med. 1993;328:1308-12.
3. Hoge CW, Shlim DR, Ghimire M, Rabold JG, Pandey P, Walch A, et al. Placebo-controlled trial of co-trimoxazole for cyclospora infections among travellers and foreign residents in Nepal. Lancet. 1995;345:691-3.