Food contamination is a constant concern in the United States, especially from imported produce.  U.S. citizens take for granted the ability to buy bananas in Montana in February.  As long as we import food, however, we must take special care to eliminate subtropical and tropical disease–causing organisms from our food.  This summer, we’re experiencing a double-threat from a parasite called “Cyclospora.”

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Cases of food contamination due to Cyclospora (known as cyclosporiasis) have been reported in more than 30 states from New Hampshire to California, with more than 3,300 infected in Michigan alone.  In most cases, fresh imported produce, especially greens and vegetables, were identified as likely origins.  Taco Bell is being investigated as a possible origin, although the FDA has not put out any public notice mentioning the chain at present.

Feces contaminated with Cyclospora can also contaminate municipal swimming pools and natural bodies of water.  Incidental ingestion of water from infected sources can sicken you.

What is Cyclospora?

Cyclospora is a one-celled parasite that naturally inhabits the tropics and subtropics, where it seems to cause seasonal outbreaks.  The U.S. cases, however, mostly 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 one to two weeks) after being passed in a bowel movement to become infectious.  The good news, therefore, is that it’s unlikely that Cyclospora can be passed directly from one person to another.  More commonly, oocysts contaminate crops or water sources.

Symptoms of Cyclosporiasis

Exactly how food and water first become contaminated with Cyclospora oocysts isn’t fully understood, but once the oocysts “hatch” in the human body, the microbes enter the intestinal wall.  That’s when symptoms begin to manifest.  They include:

• Watery diarrhea (most common)
• Loss of appetite
• Low-grade fever
• Weight loss
• Cramping
• Bloating, increased gas
• Nausea and vomiting
• Fatigue

A typical case causes illness an average of seven days after ingestion of the infective version of the oocyst.  You would expect watery diarrhea first, with frequent, sometimes explosive, bowel movements.  Vomiting, body aches, headaches, 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 the infection is not life-threatening, long-term fatigue and other problems are a possibility.

Treatment

Once the organism is identified in a stool sample, cyclosporiasis can be effectively treated with the combination sulfa drug trimethoprim-sulfamethoxazole (TMP-SMX).

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The usual regimen for adults is trimethoprim (TMP) 160 mg plus sulfamethoxazole (SMX) 800 mg (one double-strength tablet) twice daily for seven to ten days.  U.S. brands names include Bactrim and Septra.  Expect improvement two or three days after starting treatment.

No effective alternatives have been identified yet for those allergic to sulfa drugs.  In this case, most immune-competent people will still recover without treatment with rest and good hydration.

Prevention

Avoiding any food or water that might be contaminated with feces is the best way to prevent infection.  This includes accidental ingestion of water while swimming in pools or lakes.

Fruit and vegetable handling basics include the following:

• Washing hands with soap and warm water after touching fruits and vegetables.
• Cleaning cutting boards, dishes, utensils, and countertops between the preparation of meat, poultry, and seafood and fruits and vegetables.
• Preparing all fruits and vegetables thoroughly under running water before eating, cutting, or cooking.  Some suggest one part white vinegar to three parts water as an alternative.
• Removing 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.
• Storing properly by refrigerating cut, peeled, or cooked fruits and vegetables within two hours (preferably sooner).
• Separate the storage of fruits and vegetables and raw meat, poultry, and seafood.

Pool safety tips include the following:

• Avoid swallowing pool water.
• Don’t go swimming within two weeks of diarrheal symptoms.
• Pools should use proper filtration, be regularly maintained, and consider UV or ozone disinfection if possible.  

Good hygiene (showering before swimming, frequent bathroom breaks) helps reduce risk.

There are good reasons to follow the above guidelines.  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 [FDA]’s 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 is a physician, medical preparedness advocate, and N.Y. Times bestselling author of The Survival Medicine Handbook: The Essential Guide For When Help Is NOT On The Way and other books on survival medicine.

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Image via Picryl.