What is Cyclospora?

Cyclospora is a one-celled parasite too small to be seen with the naked eye (only 8 to 10 microns in diameter). Its full name is Cyclospora cayetanensis. It used to be called by such names as cyanobacterium-like, coccidia-like and Cyclospora-like bodies (CLBs).

The first known cases of Cyclospora infection were diagnosed in 1977 (reported in the medical literature in 1979). Cases have been reported with increased frequency since the mid-1980s, in part because of the availability of better techniques for detecting the parasite in stool samples. During the spring of 1996, there was a multistate outbreak of Cyclospora, including cases and suspect cases in northeastern Illinois. Investigations in other states have linked infection to the consumption of strawberries or raspberries. Very few cases are reported each year in Illinois. Because Cyclospora is a newly recognized infectious organism, many questions about its biology, the ways it is spread and the illness it causes remain unanswered.

How is Cyclospora spread?

Cyclospora is spread by a person putting something in his or her mouth that was contaminated with infected stool. For example, the parasite can be transmitted by swallowing contaminated water or food. It is not known how common the various modes of transmission are, nor is it known whether animals can be infected and can serve as sources of infection for humans.

In contrast to many other organisms, Cyclospora is not infectious at the time it is passed in the stool of an infected person. In fact, the parasite does not become infectious until days to weeks after it is passed in the stool (the amount of time depends on factors such as temperature and humidity). Therefore, spread of Cyclospora directly from an infected person to someone else is unlikely. However, so-called indirect spread might occur. For example, Cyclospora might be spread if the stool of an infected person contaminates something in the environment (e.g., water) to which someone else is exposed after the parasite has had time to become infectious.

Who is at risk for infection?

Persons of all ages are at risk for infection. Although travelers to tropical countries may be at increased risk, infection can be acquired in such countries as the United States and Canada. The risk may vary with season. Some evidence suggests that infection is most common in spring and summer.

What are the symptoms of infection?

Cyclospora infects the small intestine and typically causes an illness characterized by watery diarrhea, with an average of about six to seven stools per day. Other symptoms can include loss of appetite, weight loss, bloating, increased gas, stomach cramps, nausea, vomiting, tiredness, muscle aches and low-grade fever. Some persons notice flu-like symptoms before they notice the gastrointestinal symptoms. Some persons infected with Cyclospora do not develop any symptoms.

The length of time between becoming infected and developing symptoms probably averages at least several days and quite commonly is about a week. However, both shorter and longer intervals have been reported. If not treated, the illness may last for a few days to a month or longer and may come back one or more times. It is not known whether persons with compromised immune systems, such as persons who have AIDS, more commonly develop severe illness if infected with Cyclospora.

What should you do if you think you may be infected?

If you think you may be infected with Cyclospora, you should consult your physician. Identification of this parasite in stool requires special kinds of laboratory techniques that are not routinely used. Therefore, your physician should specifically request testing for this parasite. More than one stool sample may need to be checked to find the organism. Your physician also may want to have your stool checked for other infectious organisms that can cause similar symptoms.

How is the infection treated?

Infection with Cyclospora is treatable with antibiotics. Infected persons who have diarrhea should rest and drink plenty of fluids. They should seek their physician's advice before taking a medication to slow their diarrhea.

How can infection be prevented?

Based on the currently available information about how Cyclospora infection is spread, avoiding food and water that may be contaminated with stool probably is the best way to prevent infection. In addition, produce should be washed thoroughly before it is eaten. Infected persons should wash their hands often to prevent the spread of infection. Persons who have previously been infected with Cyclospora can become infected again.