March 24, 2018

Is Cyclospora Outbreak Source Restaurant Lettuce Salad?

Is the source of a multi-state Cyclopora outbreak restaurant lettuce salad? Health officials in at least six states are working in collaboration with the Centers for Disease Control and Prevention to divine the food source that has infected hundreds of people with a rare parasite.

cyclospora-outbreak-384The bug is so rare that it is not included in the standard parasite screening which looks for Giardia and Cryptosporidium, said David Warshauer, deputy director of communicable disease at the Wisconsin State Laboratory of Hygiene (WSLH). And once it’s confirmed with a special lab test, sub-typing is generally not performed.

With common bacterial food poisoning outbreaks, including those caused by E.coli, Salmonella, Listeria or Campylobacter, subtyping, often done with Pulsed Field Gel Electrophoresis (PFGE), is performed to find the bacteria’s “genetic fingerprint.” This allows health officials to see how many people have been sickened by the same source.

But Cyclospora is so rare that when cases pop up it is assumed they are related and sub-typing is generally not performed. For example, in Nebraska, 63 people have been diagnosed with Cyclospora infections this month, but since 2007 the state has only seen two other cases.

Nebraska is one of at least six states under siege by the single-cell parasite that can cause months of diarrhea, vomiting, weight loss and fatigue as it sets up shop in its only host: the human body. Other states reporting cases are Iowa (109), Illinois (2), Kansas (1), Texas (56) and Wisconsin (4).

Although a specific food source has not yet been identified, health officials have narrowed the field to a vegetable that was not grown in the Midwest. In the past, U.S. outbreaks of Cyclospora have all been linked to produce imported from more tropical climates where the parasite is most common. Restaurant lettuce has been mentioned in some patient interviews.

Iowa and Nebraska are both on record saying none the vegetables being investigated was grown in those states because the time of exposure was too early. “Whatever this food was, it was eaten in early June, long before Iowa fruits and vegetables came on the market,” Dr. Patricia Quinlisk, Iowa’s State Epidemiologist told Food Poisoning Bulletin today. Iowa, which has 109 cases as of July 19, has had so much testing to do that Wisconsin, which so far has four cases, is helping.

The only effective treatment for a Cyclospora infection is an antiobiotic that contains sulfa called Trimethoprim/sulfamethoxazole (TMP/SMX) which is sold under the brand names Bactrim, Septra and Cotrim. For patients with a sulfa allergy, treatment usually involves supportive care of symptoms until the body builds enough of an immune response to get rid of the parasite which can take weeks or months, said Warshauer. “It is one of the more long-lasting ones.”


  1. Please not Olive Garden salad!

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