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It’s the worst cyclosporiasis outbreak in the U.S. on record, and it could take a while before it eases. What’s more, the little parasite that’s creating misery across 9 states, mostly in the Midwest, doesn’t behave like the usual bugs that cause diarrhea in humans; bugs like norovirus, listeria, E. coli and salmonella.
“Cyclosporiasis can take weeks or even a month or longer to clear,” says Dr. Carl Crawford, a physician-scientist specializing in gastroenterology and an Assistant Professor of Clinical Medicine at Weill Cornell Medicine. “Just when you think you’re getting better, the symptoms typically roar back with a vengeance.”
Often, he explains, people get diarrhea after they’re exposed to undercooked meat or when they return from exotic travel. They can also catch a GI infection from another person. That’s what happens with norovirus, for example—a food-borne infection that can be transmitted between humans. A simple handshake can lead to several days of nausea, vomiting and diarrhea. By contrast, cyclospora doesn’t spread between people.
In what follows, Dr. Crawford puts the outbreak in perspective, from transmission to symptoms, testing and treatment, along with the parasite’s ability to interfere with the proper functioning of our digestive system.
With all the alarming reports about the outbreak, cyclospora is relatively rare compared to other food-borne bugs. Cyclosporiasis, the disease the parasite causes, is fairly rare as well. As of late July, the Centers for Disease Control and Prevention (CDC) confirmed roughly 4,100 cases nationwide.
That number, says Dr. Crawford, is probably underestimated. For one, many of the usual tests designed to identify the cause of a patient’s diarrhea don’t include cyclospora. Also, people with symptoms may consider a visit to their doctor’s office unnecessary, believing they can take care of the problem at home.
While cyclosporiasis can be extremely unpleasant, it’s rarely lethal, he says. And there’s more good news: The infection responds to treatment with antibiotics when they’re administered early enough.
Large farms and food processing or distribution hubs
The parasite tends to hide in human feces, which may contaminate the soil and irrigation water used to grow fruits and vegetables. Large farms are a likelier source of contaminated produce than smaller ones, he says, but a processing or distribution facility could also be the source of the problem.
Reduced surveillance
Nowadays, the FDA is understaffed and underfunded, and the CDC’s surveillance team that tracks food-borne infections, called FoodNet, has been downsized as well. Earlier, FoodNet routinely tracked eight pathogens, including cyclospora, but that number is now down to two: salmonella and Shiga toxin-producing E. coli. The remaining six are now considered optional.
Climate change
Cyclospora thrives in warm, moist conditions. The warmer, longer and rainier summers we’ve been experiencing as a result of climate change provide a window for the parasite to stick around for a longer period of time than in the past.
Inadequate testing
As mentioned above, the usual tests doctors use to identify the cause of diarrheal disease don’t always include cyclospora. Therefore, an ordering physician needs to have a high index of suspicion and awareness to order the correct test that can identify cylospora.
Contaminated produce
The usual culprits are leafy greens, fresh herbs and raspberries. These have been the source of cyclospora infection in the past. Shredded iceberg lettuce has been a suspected purveyor of the parasite this year.
The most common symptoms are:
Less common symptoms may include:
Dr. Crawford describes what happens once cyclospora enters our body.
“The parasite hatches, burrows into the cells that line the small intestine, reproduces, and destroys enough of them to sabotage our digestion. The small intestine is responsible for absorbing nutrients as well as electrolytes and fluids. When cyclospora takes hold there, food and drink can’t get processed in the right way, and that dysfunction can last for weeks and even up to two months.”
By contrast, diarrheal diseases caused by other food-borne pathogens tend to last just a few days and tend to affect the large intestine.
Healthy individuals with a strong immune system may have minimal symptoms, while others may be at risk for severe dehydration, electrolyte imbalance and the loss of fluid volume in the body. At-risk groups include:
Although standard tests for diarrheal disease don’t include cyclospora, physicians are onto the problem now. More and more of them are requesting the cyclospora test in light of the current outbreak.
As it turns out, the best, most accurate test, called the BioFire Assay, is on offer at Weill Cornell Medicine. It detects a pathogen’s DNA, and the results are available within a few hours or so.
There’s also good news about treatment. A tried-and-true antibiotic, Bactrim (sulfamethoxazole and trimethoprim), if administered early, will shorten the course of a cyclosporiasis infection to just one week as opposed to more than a month.
Taylor Farms, a large producer of iceberg lettuce, is still under investigation, but it’s not a foregone conclusion that it’s the main source of the current outbreak. In fact, there have been outbreaks in the past for which no source was ever found.
As well, the parasite has a long incubation period. That means the symptoms of cyclosporiasis can take a week or two to appear after it’s ingested. “People can’t remember what they ate one or two weeks earlier, making it difficult to trace the specific source of the outbreak,” Dr. Crawford says.
Cyclospora “unfortunately sticks like glue or Velcro to certain fruits and vegetables,” Dr. Crawford says. It’s a good idea, then, to make a habit of the following food safety practices, at least until the outbreak is officially over, to avoid piggy-backing onto other food-borne pathogens. For instance:
And if you have watery, explosive diarrhea, the main symptom of cyclosporiasis, make sure to drink plenty of water and seek out your physician.
Cyclosporiasis usually winds down in September, when the temperature and humidity tend to ease enough for the parasite to be deprived of the weather conditions it requires to thrive.
Find a physician at Weill Cornell Medicine at https://weillcornell.org/doctors.
