Cyclospora Infection: What it is, where it came from, and why you want to avoid it.

Cyclospora_cayetanensisRecently, the Centers for Disease Control and Prevention (CDC) issued warnings concerning infection by a parasitic protozoan named Cyclospora cayetanensis. This pathogen was first identified in the late 1970s, making it a relative newcomer in the realm of human misery. The protozoan was first identified as a form of blue-green algae, and later as a form of Cryptosporidium (the cause of cryptosporidiosis), before being properly identified and cataloged as a pathological protozoan. The Food and Drug Administration of the United States (FDA) recently (2017) banned some cilantro for Mexico due to the use of infected human waste used to fertilize some fields.

Since its first discovery, Cyclospora has been identified as the cause of some cases of where patients complained of severe diarrhea, abdominal cramping, nausea, and weight loss. In cases of early diagnosis, treatment is relatively straightforward and often consists of antibiotics, (Sulfamethoxazole/trimethoprim), or in cases of allergy to sulfa drugs, Ciprofloxacin (a non-sulfa antibiotic) can be used. Cyclospora can only be positively identified through Laboratory test of stool, and identification they require samples over the course of several days. Likely symptoms include frequent watery diarrhea, loss of appetite and weight loss, bloating and flatulence, stomach cramps, fever, and bouts of constipation. Some people will experience muscle aches and fever as well as a general fatigue. In developing countries, diarrheal diseases can be a significant threat to health, however safe drinking water may not always be available. To assess dehydration watch for dry mouth and tongue, reduced tear production, decreased urine output it, and in severe cases, sunken eyes. Dehydration is a serious symptom and may require hospitalization for intravenous fluids for some patients due to high risk of desiccation, including people suffering from serious illnesses, aged adults, and especially infants and small children.

Epidemiology. Cyclospora infection has only one known path, ingesting the protozoans in contaminated food or water. For this reason, outbreaks are reported following the consumption of contaminated fruits and vegetables. Because the protozoan is most common in tropical and subtropical regions, recent cases in the United States have been linked to imported produce coming from Central America and included cilantro, basil, lettuce, snow peas, and even raspberries. Investigators discovered that some farmers were using human excrement to fertilize fields, thus spreading the disease. When an Oocyst (an encapsulated egg-shell-like structure that allows the Cyclospora zygote a protective environment to transfer to a new host) is ingested, either suspended in water or on food, it enters the small intestine where it attaches to the mucosa (intestine wall) where it incubates for a week or so. The Oocyst emerges in the gastrointestinal tract, freeing the sporozoites that invade the epithelial cells of the small intestine. Inside the cells they undergo asexual multiplication and sexual development to mature into Oocyst, which will be shed in waste before emerging as adult protozoa. There has never been a better time to start your kitchen garden.

Pathology. In cases where Cyclospora infection is not identified and treated, chronic complications can occur such as Guillain-Barre Syndrome, acalculous cholecystopathy (a form of inflammation of the gallbladder), biliary disease (a form of biliary cirrhosis damaging the liver), and Reiter’s Syndrome (a form of reactive arthritis that develops as the immune system attempts to rid the body of the infection). Cyclospora infection is a nationally notifiable disease in the United States. The National Notifiable Diseases Surveillance System is a nationwide collaboration that enables all levels of public health, from local to international, to monitor, control, and prevent the occurrence and spread of infectious and noninfectious diseases. The CDC urges healthcare providers to watch for cases where patients have prolonged or reoccurring symptoms including watery diarrhea, particularly if they have recently traveled to tropical and subtropical regions. If such cases occur, health care providers should consider ordering a test for Cyclospora infection, however, most laboratories in the United States do not routinely test for Cyclospora, even when a stool sample has been tested for parasites in general. Therefore health  providers must request this test specifically.

New Cases in the U.S. Since May 1 of 2017, over 200 new cases of cyclospora infection have occurred. This is more than double the total new cases for the same period in 2016 according to the CDC.  The CDC reported that cases were reported in nearly 30 states. Of the 200 cases, nearly 20 patients were hospitalized.

Prevention. As the CDC points out, prevention is limited to avoiding food or water that may be contaminated, and to observe safe food handling procedures including thoroughly washing all fruits and vegetables will help, but may not remove all of the organisms. Cyclospora is often not killed by currently used disinfectants, and its ability to transmit as an Oocyst makes it a difficult protozoan to prevent. Primary risk factors include traveling in developing countries, as Cyclospora infection can be found worldwide, and anyone consuming food or water contaminated with this protozoan can be infected.


For more information, or to learn about other protozoans and parasites, go to the CDC website at

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