SACHA PFEIFFER, HOST:
Over the past three months, Cyclospora has been wreaking havoc on the digestive systems of thousands of people in the United States, and that's just confirmed cases of the illness. The true number is probably a lot higher. It's the biggest outbreak of this parasite the U.S. has ever seen. What exactly is it doing to the body? NPR's Pien Huang takes us on its internal journey.
PIEN HUANG, BYLINE: Cyclospora is a single-celled parasite. On a piece of lettuce, they would be very hard to see.
VERN CARRUTHERS: It would take about a hundred of them linked end-to-end to fit across the head of a pin.
HUANG: Vern Carruthers is a microbiologist who researches parasites in the immune system at the University of Michigan Medical School. His state is ground zero for the summer's biggest outbreak of cyclosporiasis, the disease caused by the parasite, where more than 10,000 people have eaten something like lettuce contaminated with microscopic pods. Carruthers calls them spores.
CARRUTHERS: Once swallowed, the spores respond to signals in the gut, like body temperature, probably bile, digestive enzymes, and this causes the parasites to be released from the spore.
HUANG: The parasites go straight for the small intestine, where they burrow into the lining. Carruthers says they take over the cells and use them to make copies of themselves.
CARRUTHERS: And these grow from just a few of the parasites that we would take in to millions of parasites replicating inside our intestinal cells.
HUANG: After a while, some of those parasites turn into egg and sperm-like forms, which combine to form new microscopic pods. Joel Barratt at the Emory University School of Medicine used to lead a lab team at the Centers for Disease Control and Prevention that responded to parasitic outbreaks. He says this whole process messes with your intestinal lining.
JOEL BARRATT: It does things like reduces nutrient absorption. It causes a nausea. You know, it causes that diarrhea.
HUANG: Just 1 milliliter of that diarrhea can contain around a thousand of these parasite pods. As far as scientists can tell, the only way people get sickened by Cyclospora is by inadvertently ingesting these pods in food or water contaminated with traces of human waste. But not when they're fresh, Barratt says.
BARRATT: They have to sit out there in the environment and mature. And when they mature, then they become infectious.
HUANG: These cyclospora pods can hang out in water or in crops, surviving chlorine, sunlight and cold temperatures. Dr. Bobbi Pritt, a microbiologist at Mayo Clinic, says inside the body, Cyclospora infections can last for weeks or months.
BOBBI PRITT: It's much more complex than, say, the typical viral bug - stomach bug that you can pass in a day or two.
HUANG: Antibiotics can help. They stop the parasites from replicating, giving the immune system a better chance to clear them. Cyclosporiasis isn't typically fatal and people seem to have milder infections in places where it's endemic. Still, in the U.S., it's been causing more suffering in recent years. Pritt says a major reason is that the U.S. gets produce from all over the world, but it's a mystery why it's so widespread this year.
PRITT: It might just have been bad luck with a large dose that was put into products that just happened to be high consumables.
HUANG: High consumables, destined for big chain restaurants like Taco Bell, whose shredded lettuce from Taylor Farms in Central Mexico has been linked as one source. Public health authorities are still working to figure out the rest of them. In the meantime, they recommend washing and cooking fresh vegetables to cut your risk of a gut-busting infection. Pien Huang, NPR News.
(SOUNDBITE OF SONG, "IN THE PINES")
RENEE FLEMING: (Singing) The longest train I ever saw. Transcript provided by NPR, Copyright NPR.
NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.
