Cyclospora Cayetanensis Diagnosis
The number of Cyclospora outbreaks in the United States have been unusually high this summer. Furthermore, the number of domestically obtained cases have increased since the beginning of the summer and continue to. The CDC published on July 23, 2019, “580 laboratory-confirmed cases of cyclosporiasis were reported to CDC by 30 states, District of Columbia and New York City in people who have become ill since May 1, 2019 and who had no history of international travel during the 14-day period before illness onset”. While these cases have not been caused by personal travel, many are caused by importation of food. One Cyclospora outbreak which has affected multiple states this summer has been linked to imported fresh basil from Siga Logistics de RL de CV of Morelos, Mexico. The CDC says, however, that many suspected cyclospora cases have not been able to be linked to particular outbreaks due to “lack of validated molecular typing tools for C. cayetanensis”.
Cyclospora caytanensis is a coccidian parasite that was first discovered in 1977. The parasitic protozoa are commonly found in sporulated oocysts on fresh produce such as cilantro, raspberries, and basil. Sporulated oocysts means the parasitic zygotes (fertilized and developed) are contained in a sort of cyst of bundle on the fruit. C. caytanensis must be sporulated (fertilized and matured) in order to be infective. Once ingested, the oocysts infect the epithelial tissue in the intestinal tract and rapidly reproduce sexually and asexually. The unsporulated oocysts are excreted through the feces and then the cycle begins again.
Many cases of Cyclospora go undiagnosed however, due to the difficulty to detect the oocysts in regular stool tests. Often times not enough oocysts are present in one specimen for detection and require multiple samples within consecutive days. In addition to multiple specimens, cyclospora detection requires special laboratory testing procedures that are performed, aside from regular stool testing, only upon request. These methods include staining using modified acid-fast or modified safranin, ultraviolet fluorescence microscopic detection, and polymerase chain reactions.
While these methods make cyclospora detection and linkage possible, it can be difficult and inconsistent. For this reason, it is important for patients to be proactive when experiencing food poisoning symptoms and to consider requesting cyclospora stool testing.