Cyclosporiasis Diarrhea

Laurie Anne Walden, DVM

Cyclospora cayetanensis organisms in a stool sample. Public domain image from CDC/DPDx - Melanie Moser.

Human outbreaks of diarrhea caused by cyclosporiasis have been reported across the United States this summer. Hundreds of cases have been reported in North Carolina. Most of these have been in Wake County, but some have also been reported in Mecklenburg County.
 
Cyclosporiasis is a human disease. This disease doesn’t affect dogs and cats, although similar intestinal infections cause diarrhea and vomiting in animals.
 
No cases of cyclosporiasis in humans have been linked to animal transmission. Still, it’s best to practice good hand hygiene and dispose of animal waste properly; other parasites that are common in animals can infect people.
 
Cause
Cyclosporiasis is caused by infection with Cyclospora cayetanensis, a protozoan parasite. Cyclospora are types of coccidia, so they’re related to the coccidia that infect dogs, cats, and other animals. Coccidia are host specific: each species of coccidia typically infects only one host species. Humans are the host species for C cayetanensis.
 
How Cyclosporiasis Spreads
Cyclosporiasis spreads through contaminated food and water. Cyclospora organisms that are passed in human feces enter the environment, where they develop into a form that can infect other people. The organisms aren’t spread directly from person to person; they need a week or two in the environment to become infectious.
 
The most common sources of infection are fresh vegetables and fruits. We don’t yet know all of the sources of this summer’s outbreaks. Iceberg lettuce from one supplier has been recalled so far.
 
Signs in People

• No signs (some people carry and spread C cayetanensis without getting sick)
• Watery diarrhea
• Loss of appetite
• Weight loss
• Stomach pain
• Bloating and gas
• Nausea
• Fatigue
• Vomiting
• Headache
• Fever

 
Treatment and Prevention
Like coccidia infections in animals, cyclosporiasis in people is treated with antibiotics. In some people, the illness improves without treatment.
 
The US Food and Drug Administration recommends these steps:

• Watch for announcements about recalled foods and foods to avoid.
• Wash hands with soap and warm water before and after handling food.
• Rinse fresh produce under running water.
• Peel away and discard outer layers of fruits and vegetables.
• Be aware that prewashed and precut produce might still be contaminated.
• Cook produce that can be cooked to at least 158 °F.
• Clean cutting surfaces, countertops, and utensils with hot soapy water.
• Contact your health care professional if you get sick, especially if you have diarrhea that lasts longer than three days.

 
Precautions With Pets
Seek veterinary care if your pet has diarrhea that lasts longer than a couple of days or if your pet has other signs like vomiting, belly pain, or loss of appetite. Dogs and cats are very unlikely to be infected with C cayetanensis. Pets that eat fresh produce—guinea pigs, other rodents, and reptiles, for example—are also not host species for this parasite and have not been found to be at risk of infection. However, lots of other infections cause diarrhea in animals.
 
Animals have not been shown to transmit cyclosporiasis to people. Cyclospora organisms have been detected in the feces of dogs that swallowed the organisms, but whether these organisms can actually infect people is unclear. Animals carry many other infectious organisms that can make people sick, so use general precautions: wash hands before eating and after handling animals or their feces, pick up your dog’s stool and dispose of it properly, disinfect surfaces in contact with animal feces, and give your pets the parasite prevention products that your veterinarian recommends.
 
For More Information

• Cyclospora (FDA): https://www.fda.gov/food/foodborne-pathogens/cyclospora
• Cyclosporiasis in North Carolina (NCDHHS): https://www.dph.ncdhhs.gov/blog/2026/07/14/cyclosporiasis-north-carolina-what-it-and-how-stay-safe

 
Image source: https://wwwn.cdc.gov/phil/Details.aspx?pid=7827

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