COLUMBUS, Ohio — A parasitic illness known for causing weeks of severe gastrointestinal symptoms is surging across Ohio, with northwest Ohio particularly hard hit.

More than 1,100 positive Cyclospora test results have been reported in northwest Ohio as a surge in illnesses linked to the microscopic parasite prompts food safety experts at The Ohio State University College of Food, Agricultural, and Environmental Sciences (CFAES) to help Ohioans understand the risks and reduce potential exposure.

With no confirmed food source identified, CFAES experts are moving quickly to share research-based guidance on symptoms, testing and food safety precautions. For ongoing updates, visit the CFAES cyclosporiasis resource center.

Ohio State University Extension, CFAES’ outreach arm, has brought together food safety specialists and is using its statewide network to share information as the investigation evolves.

“When this issue became more prevalent throughout the state, we immediately started looking at how Extension can best share information quickly among our staff members and with community members,” said David Civittolo, associate dean and director of Extension.

The Toledo-Lucas County Health Department reports 1,119 positive test results across northwest Ohio, including 638 in Lucas County, thus far. State and local totals may differ because health agencies use different reporting systems and update their counts at different times. The Ohio Department of Health reported 177 confirmed cases statewide as of July 2.

Cyclospora is a microscopic parasite that causes cyclosporiasis, an intestinal illness most often associated with contaminated food or water.

“It is typical to see cyclosporiasis cases surge in the spring and summer months,” said Nicole Arnold, assistant professor and food safety field specialist with Extension.

The primary symptom is frequent, watery and sometimes explosive diarrhea that can come and go for weeks. Other symptoms include loss of appetite, bloating, cramping, weight loss, nausea and fatigue.

The illness typically develops about one week after exposure but can take two weeks or longer, making diagnosis and outbreak investigations more difficult.

“If you see a healthcare provider, it is imperative to ask for testing,” Arnold said. “Any confirmed cases of cyclosporiasis are helpful to the outbreak investigation.”

Cyclosporiasis can be treated with antibiotics, she said.

Why Cyclospora is difficult to trace

The parasite’s life cycle also complicates efforts to identify an outbreak source, said Sanja Ilic, a CFAES food safety expert whose research focuses on the microbial safety of fresh fruits and vegetables.

Cyclospora requires time in the environment, often in contaminated water or soil, to become infectious. Fresh produce can then become contaminated through contact with affected irrigation water or soil.

Foods linked to previous outbreaks include leafy greens, cilantro, basil, snow and snap peas, berries, and green onions.

“Cyclospora outbreaks are difficult to trace because the parasite has a long incubation period, making outbreak investigations heavily dependent on patient recall, which becomes unreliable with time,” Ilic said.

Fresh produce also has a short shelf life, meaning potentially contaminated products may be gone by the time illnesses are identified. Cyclospora testing is not routinely performed in many clinical laboratories, Ilic said.

While no specific grower, supplier or product has been confirmed as the source of the illnesses affecting Ohioans, investigators in neighboring Michigan have identified lettuce or salad greens as a potential source of illnesses there. Other foods have not been ruled out.

Reducing risk while the investigation continues

CFAES experts say consumers should use additional care when handling and eating fresh produce and herbs.

“Cook produce and herbs when you can,” Arnold said. “Cyclospora dies at 158 degrees Fahrenheit or higher.”

Consumers should continue washing fresh produce and herbs under clean running water. Washing may reduce risk but does not guarantee the parasite will be eliminated, Ilic said. 

Consumers seeking additional precautions may choose to avoid eating raw produce historically linked to cyclosporiasis. Those precautions are particularly important for young children, older adults and people with weakened immune systems or certain underlying health conditions, Ilic said. Prolonged diarrhea can lead to dehydration and other complications.

“If consumers or anyone in their family experience symptoms, they should see their healthcare provider,” Ilic said.

Arnold said consumers should also consider potential exposure when eating away from home because restaurants and other food businesses may serve raw produce or fresh herbs.

“The current source of the cyclosporiasis outbreak is unknown,” Arnold said. “You should take additional steps for fresh produce and herbs that you purchase from stores, and you should also take precautions when eating out.”

Extension’s presence in all 88 Ohio counties helps the university quickly translate evolving research and public health information into practical guidance, Civittolo said.

“Our Extension professionals live and work in the communities they serve, and this means we have an existing network of trusted Extension staff members who already know whom to contact within each community,” he said.

That network, combined with Extension’s food safety expertise and relationships with public health professionals, helps CFAES interpret emerging information and provide guidance quickly.