Cyclosporiasis is infection with the protozoan Cyclospora cayetanensis. Symptoms include watery diarrhea with gastrointestinal and systemic symptoms. Diagnosis is by detection of characteristic oocysts in stool or intestinal biopsy specimens. Treatment is with trimethoprim/sulfamethoxazole (TMP/SMX).
(See also Overview of Intestinal Protozoan and Microsporidia Infections.)
Cyclosporiasis is caused by an obligate intracellular protozoan. Transmission is by the fecal-oral route, usually via contaminated food or water. This infection is most common in warm climates where sanitation is poor. Residents of and travelers to endemic areas are at risk.
Cyclospora cayetanensis outbreaks have been increasingly documented in the United States, Canada, and Europe. In the United States, there are approximately 1000 to 2000 cases of cyclosporiasis reported to the Centers for Disease Control and Prevention (CDC) each year (see CDC: Outbreak Investigations and Updates), and more cases may go unreported. Cyclosporiasis outbreaks usually occur in summer and are associated with consumption of fresh produce such as raspberries, blackberries, strawberries, blueberries, basil, cilantro, snow peas, snap peas, prepared vegetables, and various lettuces (1). In 2019, the U.S. Food & Drug Administration (FDA) and CDC created the Cyclospora Task Force to address the increase in outbreaks as well as the emergence of C. cayetanensis in domestically grown produce in the United States (see FDA: Cyclospora Prevention, Response and Research Action Plan).
Image from the Centers for Disease Control and Prevention, Global Health, Division of Parasitic Diseases and Malaria.
The life cycle of C. cayetanensis is similar to that of Cryptosporidium, except that oocysts passed in stool are not sporulated. Thus, when freshly passed in stools, the oocysts are not infective, and direct fecal-oral transmission cannot occur. The oocysts require days to weeks in the environment to sporulate and, therefore, direct person-to-person transmission is unlikely. The sporulated oocysts are ingested in contaminated food or water and excyst in the gastrointestinal tract, releasing sporozoites. The sporozoites invade the epithelial cells of the small intestine, replicate, and mature into oocysts, which are shed in stool.
General reference
1. Mathison BA, Pritt BS. Cyclosporiasis-Updates on Clinical Presentation, Pathology, Clinical Diagnosis, and Treatment. Microorganisms. 2021;9(9):1863. Published 2021 Sep 2. doi:10.3390/microorganisms9091863
Symptoms and Signs of Cyclosporiasis
The primary symptom of cyclosporiasis is sudden, nonbloody, watery diarrhea, with fever, abdominal cramps, nausea, anorexia, malaise, and weight loss. In immunocompetent patients, the illness usually resolves spontaneously but can last weeks. Relapses may follow improvement in symptoms.
In hosts with depressed cell-mediated immunity as occurs in patients with end-stage human immunodeficiency virus (HIV), cyclosporiasis may cause severe, intractable, voluminous diarrhea resembling cryptosporidiosis. Extraintestinal disease in patients with end-stage HIV may include cholecystitis and disseminated infection.
Diagnosis of Cyclosporiasis
Microscopic examination of stool for oocysts
Detection of parasite DNA in stool
Diagnosis of cyclosporiasis is by stool tests, either molecular testing for parasite DNA or microscopic examination for oocysts. A modified Ziehl-Neelsen or Kinyoun acid-fast staining technique can help identify Cyclospora. Oocysts of Cyclospora are autofluorescent. Cyclospora oocysts are spherical and similar in morphology to but larger than Cryptosporidium oocysts.
Multiple (≥ 3) stool specimens may be needed because oocyst secretion may be intermittent.
The molecular diagnosis of C. cayetanensis is primarily via multiplex assays for a variety of gastrointestinal pathogens.
Diagnosis is sometimes made only when intracellular parasite stages are detected in biopsies of intestinal tissue.
Treatment of Cyclosporiasis
Trimethoprim/sulfamethoxazole (TMP/SMX)
Most healthy people recover without treatment. If not treated, the illness may last for a few days to a month or longer and can relapse.
Treatment of choice for cyclosporiasis is double-strength TMP/SMX for 7 to 10 days.
In patients with end-stage HIV, higher doses and longer duration may be needed, and treatment of acute infection is usually followed by long-term suppressive therapy (one double-strength 160 mg/800 mg TMP/SMX tablet 3 times weekly) to prevent relapse. Institution or optimization of antiretroviral therapy (ART) is important.
Prevention of Cyclosporiasis
Avoiding food or water that may have been contaminated with feces is the best way to prevent cyclosporiasis.
Travelers to cyclosporiasis-endemic areas (such as tropical and subtropical regions) should be aware that treatment of water or food by routine chemical disinfection or sanitizing methods is unlikely to kill Cyclospora. (See Centers for Disease Control and Prevention [CDC]: Parasites - Cyclosporiasis: Prevention & Control and CDC Yellow Book: Cyclosporiasis). Detailed recommendations for international travelers are available in the CDC Yellow Book: Food & Water Precautions.
In endemic regions, drinking water should be boiled, unpeeled fruit should be avoided, and vegetables cooked thoroughly.
More Information
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