Merck Manual

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Chelsea Marie

, PhD, University of Virginia;

William A. Petri, Jr

, MD, PhD, University of Virginia School of Medicine

Reviewed/Revised Oct 2022 | Modified Nov 2022
Topic Resources

Cyclosporiasis is an infection of the small intestine caused by the parasite Cyclospora cayetanensis. The main symptoms are watery diarrhea with abdominal cramping and nausea.

Cyclosporiasis is most common in tropical and subtropical climates where sanitation is poor. Residents and travelers to endemic areas are at risk. In the United States, outbreaks of this infection have been attributed to imported fresh produce, such as raspberries, basil, snow peas, mesclun lettuce, and cilantro.

Symptoms of Cyclosporiasis

The primary symptom of cyclosporiasis is sudden, nonbloody, watery diarrhea, and nausea. Other symptoms include fever, abdominal cramps, vomiting, fatigue, and weight loss. Symptoms in people with a normal immune system last from a few days to a month or longer. Relapses may occur.

Diagnosis of Cyclosporiasis

  • Stool tests

To diagnose cyclosporiasis, a stool sample is examined under a microscope for Cyclospora eggs. Specialized techniques can be used to increase the chances of identifying the eggs. Molecular techniques are available in some reference laboratories to identify parasite DNA.

When stool examination does not reveal a cause of persistent diarrhea, doctors may use a flexible viewing tube (endoscope Endoscopy Endoscopy is an examination of internal structures using a flexible viewing tube (endoscope). In addition to examinations, doctors can use endoscopy to do biopsies and give treatment. Endoscopes... read more ) to examine the upper part of digestive tract and obtain a sample of tissue (a biopsy) to be examined under a microscope and analyzed for parasite DNA.

Prevention of Cyclosporiasis

When outbreaks are reported, people should avoid eating potentially contaminated fruits or vegetables from the area. When traveling to tropical and subtropical areas where the infection is common, people should avoid eating uncooked foods, including salads and vegetables, and should avoid consuming potentially contaminated water and ice. Hand washing with soap and water is important. Drinking water that has been boiled is safe. Filtering water through a 0.1 or 0.4 micron filter can remove cysts of Cyclospora and other parasites, as well as bacteria that cause diseases.

Treatment of Cyclosporiasis

  • Trimethoprim/sulfamethoxazole (TMP/SMX)

  • Alternatively, ciprofloxacin

Infected people who have symptoms can be treated with trimethoprim/sulfamethoxazole (TMP/SMX) taken by mouth.

Ciprofloxacin is an alternative to TMP/SMX for cyclosporiasis.

Select Medical Literature

  • 1. Abanyie F, Harvey RR, Harris JR, et al: 2013 multistate outbreaks of Cyclospora cayetanensis infections associated with fresh produce: Focus on the Texas investigations. Epidemiol Infect 143(16):3451–3458, 2015. doi: 10.1017/S0950268815000370

  • 2. CDC: Multi-state outbreak of cyclosporiasis linked to Del Monte fresh produce vegetable trays — United States, 2018.

  • 3. Casillas SM, Hall RL, Herwaldt BL: Cyclosporiasis Surveillance—United States, 2011-2015. MMWR Surveill Summ 68(3):1-16, 2019. doi:10.15585/mmwr.ss6803a1

Drugs Mentioned In This Article

Generic Name Select Brand Names
Primsol, Proloprim, TRIMPEX
Cetraxal , Ciloxan, Cipro, Cipro XR, OTIPRIO, Proquin XR
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