The intestinal parasite Cyclospora cayetanensis has a dramatically increased infection rate this summer, and the source is still unknown, the CDC advised today. 2017 is a good year for Cyclospora looking for homes to start their families and a bad year for those of us who don't like food-stealing tenants living in our bodies.
Between May 1 and August 3, there have been at least 206 cases of cyclosporiasis reported to the CDC, compared to only 88 cases last year at this time. While there have been no deaths, 18 of the cases have required hospitalization. One of the states most affected by the current uptick is Texas, and the Texas government issued a news release warning residents on July 17, after 68 new cases popped up in a four-week stretch.
The parasite Cyclospora is more common in tropical and subtropical areas; it causes cyclosporiasis — a rarely fatal, but very unpleasant infection. Symptoms include watery diarrhea, weight loss, loss of appetite, nausea, fatigue, cramping, bloating, and gas. They start between two days and two weeks after ingestion, averaging about a week.
Most people get better on their own, but cyclosporiasis can be more severe and prolonged for those with weakened immune systems. Doctors can use the antibiotic trimethoprim/sulfamethoxazole to shorten the illness. Anti-diarrheal medicine can also be used, with a healthcare provider's guidance, to reduce diarrhea in the meantime.
In the past, Cyclospora infections have originated in fresh produce. UK cases this year have been linked to travel to Mexico, but it is not clear that the same applies to the current US outbreak. In past US outbreaks, items like fresh produce, including fresh pre-packaged salad mix, raspberries, basil, snow peas, and mesclun greens, have been implicated in spreading the parasite. Past Texas outbreaks are thought to be due to infected cilantro.
The way to avoid Cyclospora is to be careful of the fresh produce and water you consume. That remains difficult at this point though, until we know the particular source (or sources) are spreading the parasite. So in the meantime, watch out for symptoms and go to a healthcare provider if you get sick with something that might be cyclosporiasis.
Cyclospora oocysts, once ingested, can find their way through our cell walls. Two sporozoites, the worm-like life phase of Cyclospora, emerge from each oocyst and wriggle their way into the epithelial cells of a host's small intestine. There they can multiply inside the cell asexually, undergo sexual development, and form more oocysts which get into the environment through fecal matter. At first, the released oocysts are harmless. But with enough time at warm enough temperatures (71.6º F to 89.6º F), the sporont inside them divides into two sporocysts each containing two sporozoites ready to burst out and invade once they're in a host again.
Healthcare providers in the state are advised by the Texas Department of Health and Human Services to test any patients who have diarrhea lasting multiple days or accompanied by fatigue or significant loss of appetite. There are a few ways to test for Cyclospora mentioned by the CDC — ova and parasite examination, molecular methods, and a gastrointestinal panel test. But testing for the parasite can sometimes need multiple stool samples, because the Cyclospora oocysts (which contain zygotes of parasitic protozoans) may not regularly shed.
If providers find Cyclospora or need assistance testing for it, they are advised by the CDC to contact their local health department. Reporting and monitoring of Cyclospora cases could help reveal the source of the parasite, so we'll finally know what foods to avoid. Until then, for those of us trying to be healthy with lots of fresh produce and hydration, Cyclospora cayetanensis could put a cramp in your style.
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