Author(s): Anne Straily, Rebecca Chancey

Infectious Agent

Cyclospora cayetanensis, a coccidian protozoan parasite, causes cyclosporiasis.

Transmission

Transmission occurs through ingestion of infective Cyclospora oocysts, typically from contaminated food or water.

Epidemiology

Cyclosporiasis occurs in many countries around the world, but appears to be most common in tropical and subtropical regions. Outbreaks frequently are seasonal, but seasonality varies in different parts of the world. In Guatemala, detection rates increase during May–August. In Nepal, rates increase during the summer and rainy season (May–October). In Turkey, incidence rates are highest during July–November. No environmental conditions (e.g., temperature, rainfall) have yet been determined to be drivers for the seasonal variation in cyclosporiasis.

People typically become infected through the consumption of contaminated fresh produce or contaminated water. All travelers are at risk of infection, regardless of the purpose or length of their travel in an endemic area; even short-term travelers can become infected. Outbreaks in the United States and Canada typically occur during the spring and summer months; historically these have been linked to consumption of imported fresh produce. No commercially frozen or canned produce has yet been implicated as the source of an outbreak.

During 2011–2015, 415 cyclosporiasis cases were reported among US residents with a history of international travel during their incubation period. The most frequently reported destinations were in the Americas, including Mexico, the Caribbean, Central America, and South America; travel to Africa, Asia, and Europe was reported less frequently among identified case-patients.

Clinical Presentation

The incubation period averages 1 week (range 2 days to ≥2 weeks). Symptom onset often is abrupt, but can be gradual; some people have an influenza- like prodrome. The most common symptom is watery diarrhea, which can be profuse. Other symptoms can include abdominal cramps, anorexia, bloating, body aches, low-grade fever, nausea, vomiting, and weight loss. If untreated, the illness can last for several weeks or months with a remitting–relapsing course.

Diagnosis

Cyclosporiasis is diagnosed by detecting Cyclospora oocysts or DNA in stool specimens. Stool examinations for ova and parasites usually do not include methods for detecting Cyclospora unless testing for this parasite is specifically requested. Diagnostic assistance for Cyclospora and other parasitic diseases also is available from the Centers for Disease Control and Prevention; 404-718-4745; parasites@cdc.gov). Cyclosporiasis is a nationally notifiable disease.

Treatment

Treatment includes trimethoprim-sulfamethoxazole; no highly effective alternatives have been identified. One case report documented resolution of symptoms after treatment with nitazoxanide in a patient with a sulfa allergy. Anecdotal data suggest that ciprofloxacin is ineffective.

Prevention

Travelers can reduce their risk for infection by following food and water precautions (see Sec. 2, Ch. 8, Food & Water Precautions), but using chlorine or iodine for water disinfection is unlikely to be effective because oocysts are extremely tolerant of halogens (see Sec. 2, Ch. 9, Water Disinfection).

CDC website: Cyclosporiasis