Locally-acquired cyclosporiasis in Ontario

Advisory Alert

July 13, 2018

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I am writing to advise you that Ontario is experiencing an increase in the number of Cyclospora infections. There have been 29 locally-acquired cyclosporiasis cases reported in the province between April 1 and July 12, 2018. We are requesting your assistance in helping with the prompt diagnosis of infected patients. Testing for Cyclospora will support prompt treatment of patients to lessen duration of symptoms, as well as assist with identifying the source of illness.

Etiology, Clinical Presentation, and Transmission

Cyclosporiasis is a gastrointestinal illness caused by infection with the parasite Cyclospora cayetanensis. It is commonly characterized by frequent watery diarrhea, as well as other symptoms such as anorexia, fatigue, abdominal cramps, nausea, and myalgia. Left untreated, symptoms typically last 6 to 7 weeks and can wax and wane in intensity.

People are infected by ingesting food or water contaminated with the parasite. Cyclospora is not endemic in Canada. Most reported cases in Ontario are infected when visiting an endemic country (e.g. in the Caribbean, South and Central America, South and South East Asia). When cases occur in individuals who did not travel (as is currently occurring in Ontario), an investigation is launched to determine potential sources of Cyclospora in imported foods. Most outbreaks in Ontario occur in the spring and summer and locally-acquired infections are likely due to fresh produce such as berries or herbs that are imported from Cyclospora endemic countries. The infection is unlikely to spread from person to person.

Diagnosis and Laboratory Testing

Cyclospora infection can be diagnosed by a stool ova and parasite (O&P) examination. For details, visit https://www.publichealthontario.ca/en/ServicesAndTools/LaboratoryServices/Pages/Cyclospora_Faeces.aspx.

If patients present with cyclosporiasis-compatible symptoms between now and the end of summer, please request testing for stool parasites on the Public Health Ontario Laboratory General Test Requisition form and specify the request is to test for Cyclospora.


First-line treatment is trimethoprim-sulfamethoxazole (TMP-SMX). Symptoms typically improve within 2 to 3 days of starting TMP-SMX.


Report any suspected Cyclosporiasis cases immediately to Public Health Sudbury & Districts for follow-up.

Should you have any questions, please contact the Environmental Health Division at 705.522.9200, ext. 398.


Ariella Zbar, MD, CCFP, MPH, MBA, FRCPC
Associate Medical Officer of Health

Additional Resources on Cyclosporiasis

This item was last modified on July 13, 2018