Outbreaks of illness in the United States causing infectious watery diarrhea, nausea, and vomiting recently have been found to be caused by a parasite called Cyclospora. Food-borne outbreaks of the illness have been reported in the U.S. since the mid-1990s, although this is a relatively uncommon cause of gastroenteritis. About one third have been associated with international travel, one third were domestically acquired, and another third were from unknown sources.
The importation of food from Central and South America, especially fruits and vegetables, has led to multiple outbreaks, including ones associated with raspberries, snow peas and snap peas from Guatemala. Outbreaks of Cyclospora infections (cyclosporiasis) in 2013 and 2014 have been linked to cilantro and salad mixes, affecting more than 600 people, mostly in Nebraska, Texas and Iowa.
The Cyclospora parasite is transmitted to people who contact objects contaminated with infected stool (mainly water and foods like fruits and vegetables that may have been washed or sprayed with contaminated water). In 1997, reports of outbreaks of Cyclospora infection were preliminarily associated with the consumption of fresh fruits, such as strawberries and raspberries, but the current outbreaks have not been associated with specific foods.
The Center for Disease Control and Prevention (CDC) works with the federal, state, and local health departments to determine the extent and causes of the recent outbreaks of Cyclospora. They pointed out that although it is prudent to thoroughly wash produce that will be eaten raw, this practice may not eliminate the risk of transmission of Cyclospora. Further, they recommend that health-care professionals consider Cyclospora infection in people with prolonged (longer than about a week) diarrheal illness and specifically request laboratory testing for this parasite.
The CDC has a site (see the CDC reference below) that is updated with information that answers the following questions about cyclosporiasis:
What is Cyclospora?
Cyclospora is a parasite that is composed of one cell. It is too small to be seen without a microscope. Its full name is Cyclospora cayetanensisa, and it has a life cycle that involves both sexual and asexual reproduction. The part of the cycle in man is the ingestion of sporulated oocysts that pass through the GI tract where the sporocysts break open in the small intestine and release oocysts that infect the GI cells. The organisms then reproduce and release unsporulated oocysts into the stool contents that are excreted into the environment where they develop into sporulated oocysts that can infect humans.
The first known human cases of Cyclospora infection were diagnosed in 1977. Cases began being reported more often in the mid-1980s. More frequent reports may be due to better techniques that are now being used to detect the parasite in specimens of stool (bowel movements).
How is Cyclospora transmitted?
Cyclospora is transmitted by a person putting something in his or her mouth that was contaminated with sporulated oocysts in water or on foods that have been exposed to human feces in the recent past. Cyclospora oocysts needs time (days or weeks) after being passed in a bowel movement to develop into an infectious organism (sporulated oocysts). Therefore, transmission of Cyclospora directly from an infected person to an uninfected person is unlikely.
Who is at risk for infection with Cyclospora?
People of all ages are at risk for infection. In the past, Cyclospora infection was usually found in people living or traveling in tropical countries. More and more, cases are being recognized in countries such as the United States and Canada. The risk may vary with season. Infection may be most common in spring and summer.
What are the symptoms of Cyclospora infection?
Cyclospora infects the small intestine and usually causes watery diarrhea (sometimes described as explosive diarrhea) with frequent bowel movements. Other symptoms include loss of appetite, weight loss, bloating, increased gas, stomach cramps, nausea, vomiting, tiredness, muscle aches, and low-grade fever. Other infectious organisms can cause a similar illness, and these symptoms are not specific for Cyclospora infection. Some people infected with Cyclospora do not develop any symptoms.
The time between becoming infected and developing symptoms is usually several days to a week, but some cases may take as long as two weeks to develop. If not treated, the illness may last for a few days to a month or longer. It may also return one or more times.
What should you do if you think you may be infected with Cyclospora?
If you think you may be infected with Cyclospora, you should consult your physician. Identification of this parasite in stool requires special laboratory tests that are not routinely used in most U.S. hospitals. Therefore, your physician should specifically request testing for Cyclospora and send stool samples to specialized laboratories. More than one stool sample may be needed. Your physician may also want to have your stool checked for other infectious organisms that can cause similar symptoms.
How is Cyclospora infection treated?
Infection with Cyclospora is treated with antibiotics. Trimethoprim-sulfamethoxazole, also known as Bactrim, Septra, or Cotrim (a combination of two antibiotics), is recommended. Infected people with diarrhea should rest and drink plenty of fluids. They should seek their physician's advice before taking medicine to slow their diarrhea.
How is Cyclospora infection prevented?
Cyclospora infection can be prevented by avoiding water or food, especially imported fruits and vegetables that may have been exposed to human feces. People who have previously been infected with Cyclospora can become infected again. There is no vaccine available to prevent Cyclospora infections.
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Chiodini, P.L. "A 'New' Parasite: Human Infection With Cyclospora cayetanensis." Trans R Soc Trop Med Hyg 88 (1994); 369-371.
Huang, P., et al. "The First Reported Outbreak of Diarrheal Illness Associated With Cyclospora in the United States." Ann Intern Med 123 (1995): 409-414.
Ortega, Y.R., et al. "Cyclospora Species - A New Protozoan Pathogen of Humans." N Engl J Med 328 (1993): 1308-1312.
United States. Center for Disease Control and Prevention. "Parasites - Cyclosporiasis (Cyclospora Infection)." Jan. 10, 2013. <http://www.cdc.gov/parasites/cyclosporiasis/disease.html>.