Food contamination is a constant concern in the United States, especially from imported produce. In normal times, U.S. citizens take for granted the ability to buy bananas in Montana in February. As long as we import food, we must be especially careful to eliminate subtropical and tropical pathogens from our food.
A number of different disease-causing organisms especially put humans at risk; one of these is Cyclospora cayetanensis. From May to late August, 2020, more than 1100 laboratory-confirmed cases of food contamination due to Cyclospora (known as cyclosporiasis) were reported in 34 states. In most cases, fresh imported produce, especially greens and vegetables, were identified as likely origins.
Cyclospora is a one-celled parasite that is a natural inhabitant of the tropics and subtropics, where it seems to cause outbreaks that are seasonal in nature. The U.S. cases, however, occurred in people who had not recently visited the tropics before symptoms began.
THE LIFE CYCLE OF CYCLOSPORA
Cyclospora is spread by people ingesting food or water contaminated with feces containing Cyclospora oocysts (essentially a thick-walled fertilized ovum). Unlike some similar parasites, however, the oocyst needs time (usually, at least 1–2 weeks) after being passed in a bowel movement to become infectious. Therefore, it’s unlikely that Cyclospora can be passed directly from one person to another. More likely, the oocysts contaminate crops or water sources.
SYMPTOMS OF CYCLOSPORIASIS
Exactly how food and water becomes contaminated with Cyclospora oocysts isn’t fully understood but, once the oocysts “hatch” in the human body, the microbes enter the intestinal wall. Some symptoms then begin to manifest. They start an average of 7 days after ingestion of the infective version of the oocyst and can include the following:
- Watery diarrhea (most common)
- Loss of appetite
- Low-grade fever
- Weight loss
- Bloating, increased gas
- Nausea and vomiting
A typical case would cause watery diarrhea, with frequent, sometimes explosive, bowel movements. Vomiting, body aches, headache, fever, and other flu-like symptoms may be noted. Interestingly, some people infected with Cyclospora have no symptoms at all.
If untreated, the illness endures for a few days, but some cases last a month. Some victims experience improvement and then relapse several times during the progress of the infection. Although not life-threatening, long-term fatigue and other problems are a possibility.
Once the organism is identified in a stool sample, cyclosporiasis can be effectively treated with the combination sulfa drug trimethoprim-sulfamethoxazole (TMP-SMX). The usual regimen for adults is trimethoprim (TMP) 160 mg plus sulfamethoxazole (SMX) 800 mg (one double-strength tablet) twice daily for 7–10 days. The veterinary equivalent is FISH-SULFA FORTE. No effective alternatives have been identified yet for those allergic to sulfa drugs. In this case, most immune-competent people will recover without treatment and with good hydration.
Avoiding any food or water that might be contaminated with feces is the best way to prevent infection. Routine chemical disinfection is less effective for Cyclospora than for most other bacteria or parasites.
Fruit and vegetable handling basics include:
1)Washing hands with soap and warm water after touching fruits and vegetables. Also, be sure to clean cutting boards, dishes, utensils, and counter tops between the preparation of meat, poultry, and seafood and fruits and vegetables.
2)Preparing all fruits and vegetables thoroughly under running water before eating, cutting, or cooking. Remove any damaged or bruised areas on fruits and vegetables. Firm items like cucumbers or melons should be scrubbed with a clean brush dedicated to the purpose.
3)Storing properly by refrigerating cut, peeled, or cooked fruits and vegetables within two hours (preferable sooner). Separate the storage of fruits and vegetables and raw meat, poultry, and seafood.
It should be noted that routine chemical disinfection is less effective for Cyclospora than for most other bacteria or parasites. No vaccine exists and immunity isn’t long-term: Recurrence of infection is not uncommon if re-exposed.
(Note: The U.S. Food and Drug Administration’s (FDA) Center for Food Safety and Applied Nutrition (CFSAN) has a special advisory called: Guide to Minimize Microbial Food Safety Hazards for Fresh Fruits and Vegetables.
Joe Alton MD