Time to Think About Cyclosporiasis

Alan D. Dowell; Barbara Herwaldt, MD, MPH


July 28, 2014

Editorial Collaboration

Medscape &


Cyclosporiasis is an intestinal illness caused by Cyclospora cayetanensis, which is a protozoan (unicellular) parasite that was characterized as recently as the early 1990s. Cyclosporiasis can occur at any time of the year. However, most of the reported cases and outbreaks in the United States have occurred during spring and summer months, especially during May through August. Therefore, clinicians should have heightened awareness about cyclosporiasis at this time of the year. In fact, as of the date of this posting, CDC is collaborating with public health officials at the federal, state, and local levels to investigate cases of cyclosporiasis reported in 2014.

In an interview for Medscape, Alan Dowell, a health communication specialist in the Division of Parasitic Diseases and Malaria at the US Centers for Disease Control and Prevention (CDC), spoke with Barbara Herwaldt, MD, MPH, a medical epidemiologist and infectious diseases specialist, also in CDC's Division of Parasitic Diseases and Malaria, about the importance of considering cyclosporiasis. Dr. Herwaldt has authored numerous reports about US outbreaks of cyclosporiasis, many of which are available online.

Alan Dowell: How is Cyclospora transmitted?

Barbara Herwaldt, MD, MPH: Cyclospora is transmitted by ingesting fecally contaminated food or water that contains the infective form of the parasite. Infected people shed an immature form of the parasite in their feces that is incapable of infecting another person. Therefore, Cyclospora is not spread directly from one person to another. The immature form of the parasite has to undergo a maturation process in the environment, which requires days to weeks under favorable conditions, to become infective.

Mr. Dowell: Is Cyclospora transmitted in the United States?

Dr. Herwaldt: Cyclosporiasis has been reported from many countries, including the United States, but appears to be mainly found in tropical and subtropical regions of the world. To our knowledge, cyclosporiasis is not endemic in the United States, although we cannot exclude the possibility of focal, low-level endemicity.

The 2 well-established risk factors for US cases of cyclosporiasis include international travel to regions where cyclosporiasis is endemic and domestic consumption of contaminated fresh produce imported from such regions. In the United States, foodborne outbreaks of cyclosporiasis have been linked to various types of imported fresh produce, such as raspberries, basil, mesclun lettuce, and snow peas. To date, no commercially frozen produce has been implicated.

Mr. Dowell: What are the symptoms of cyclosporiasis?

Dr. Herwaldt: The symptoms of this intestinal infection usually begin approximately 1 week after the exposure (sometimes sooner or later). The most common symptom is watery diarrhea, which can be profuse and prolonged. Other common symptoms include anorexia, weight loss, abdominal bloating, increased flatus, abdominal cramps or pain, and nausea. Body aches, low-grade fever, and other flu-like symptoms may be noted. Vomiting may occur but is much less common than diarrhea.

If untreated, the illness may last for days to weeks to months and the symptoms can come and go. Diarrhea may alternate with constipation. Substantial weight loss and prolonged fatigue commonly occur.

Mr. Dowell: As a parasite, is C cayetanensis detected by routine stool examinations for ova and parasites, or are special laboratory tests needed?

Dr. Herwaldt: Special, nonroutine tests are needed. The most important point for US healthcare providers to know about diagnosing cyclosporiasis is that stool specimens examined for ova and parasites, or O&P, usually are not examined for Cyclospora unless such testing is explicitly requested. Healthcare providers should consider C cayetanensis as a potential cause of prolonged or remitting-relapsing diarrheal illness and, if indicated, explicitly request stool testing for this parasite.