Cyclospora—Common Sources for Cyclospora Infection—Water. The picture on the left was viewed under dark-field microscopy; the one in the middle is a scanning electron microscopy picture not done routinely in the doctor’s office. The far right picture is a picture of four Cyclospora oocysts from fresh stool fixed in 10% formalin and stained with modified acid-fast stain.  Compared to wet mount preparations, the oocysts are less perfectly round and have a wrinkled appearance.  Most importantly, the staining is variable among the four oocysts. 

What is Cyclospora? Cyclospora infection is caused by Cyclospora cayetanensis, a newly recognized 8-10 micrometer sized microscopic one-celled intracellular coccidian parasite. It causes a disease called cyclosporiasis. Infection with Cyclospora has been increasingly reported worldwide in people with or without a strong immune system.

In 1996, a large outbreak of Cyclospora infection in the United States and Canada was caused by Guatemala-imported raspberries. It is not clear how the fruit became contaminated, but it might have happened when fruit touched the ground or when contaminated water was sprayed over fruit fields by sprinkling systems.

People infected with C. cayetanensis excrete oocysts that are not infectious. This is an important clue in diagnosis because other parasitic diseases can be very infectious so more than one person (or pet) in the family will have symptoms at the same time. Cyclospora needs days or weeks after being passed in a bowel movement to become infectious. People most likely get Cyclospora infection by ingesting food or water that was contaminated with stool from an infected person. It is unknown if animals can be infected and pass infection to people.

Cyclospora Lifecycle

Symptoms of Cyclospora: Cyclospora infects the small intestine and usually causes watery diarrhea, with frequent, sometimes explosive, bowel movements. Other symptoms can include loss of appetite, loss of weight, bloating, increased gas, stomach cramps, nausea, vomiting, muscle aches, low-grade fever, and tiredness. Some people who are infected with cyclospora have no symptoms. Symptoms show up about a week after being exposed. If not treated, the illness can last for a few days to a month or longer. If untreated, it can also return one or more times.

Diagnosis and Treatment of Cyclospora: Identification of this parasite in stool requires an acid-fast stain which is a special laboratory tests not routinely done. A health-care provider must specifically request testing for Cyclospora. Also, one negative stool specimen does not rule out infection with Cyclospora. At least three stool samples should be tested before a negative result is reported. Cyclospora infection is treated with Trimethoprim-sulfamethoxazole, an oral medicine that is a combination of two sulfa-based antibiotics.

Prevention of Cyclospora: Based on what is known about Cyclospora, the best way to prevent infection is to Wash your hands before handling food and eating, avoid eating unwashed, raw or undercooked foods or drinking untreated water that could be contaminated with stool. Cooking can kill Cyclospora, and freezing might, too. As a general food safety measure, always wash fresh produce, even if it is to be peeled before eating.

Other tips: Do not drink untreated surface water from a spring, stream, river, lake, pond or shallow well. When traveling to a developing country make sure that you drink bottled water, or boil untreated surface water that is used for drinking, making ice cubes, washing uncooked fruits and vegetable, making baby formula, brushing teeth and washing dentures or contact lenses. Boil for at least 1 minute at a rolling boil. At elevations above 2000 m (6562 ft), boil for at least 2 minutes.

References for Cyclospora:

• Good article: https://jmm.sgmjournals.org/cgi/content/full/55/4/459
• Great set of Pictures: https://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/Cyclosporiasis_il.htm 
• Cyclospora lifecycle: https://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/Cyclosporiasis_il.htm