Health care providers should consider Cyclospora as a potential cause of prolonged diarrheal illness, particularly in patients with a history of recent travel to Cyclospora–endemic areas. Testing for Cyclospora is not routinely done in most U.S. laboratories, even when stool is tested for parasites. Therefore, if indicated, health care providers should specifically request testing for Cyclospora.
Cyclospora infection is diagnosed by examining stool specimens. Diagnosis can be difficult in part because even persons who are symptomatic might not shed enough oocysts in their stool to be readily detectable by laboratory examinations. Therefore, patients might need to submit several specimens collected on different days.
Special techniques, such as acid-fast staining, are often used to make Cyclospora oocysts more visible under the microscope. In addition, Cyclospora oocysts are autofluorescent, meaning that when stool containing the parasite is viewed under an ultraviolet (UV) fluorescence microscope the parasite appears blue or green against a black background. Molecular diagnostic methods, such as polymerase chain reaction (PCR) analysis, are used to look for the parasite’s DNA in the stool.