Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at April 7, 2016

Cyclosporiasis is a type of illness that originates in the intestines. This infection can cause severe diarrhea. Cyclosporiasis is a relatively rare illness that only occurs due to the ingestion of water or food that have been contaminated by feces.


Definition & Facts

Cyclosporiasis is an infection caused by ingesting the Cyclospora parasite. This parasite is usually non-infective. However, under certain environmental conditions, the parasite can eventually become infectious, leading to numerous symptoms and health issues until treatment is sought.

This infection typically occurs when a person eats food or drinks water that has been tainted with feces. Transmission from person-to-person is exceedingly rare, as is transmission with water or food that's only recently become contaminated.

Cyclosporiasis is most common in tropical regions, as well as subtropical ones. Within the US, this parasite is most commonly found in fresh produce that's been imported from other countries, including snow peas and raspberries.

Symptoms & Complaints

Once the Cyclospora parasite has been ingested, symptoms won't appear immediately. By far the most common symptom is diarrhea which will be watery and very uncomfortable. Other symptoms like bloating and an increase in gas are also likely.

Nausea and fatigue are relatively common as is a general loss of appetite. Due to the presence of diarrhea and other symptoms, many people with this illness will experience unintentional weight loss before treatment is received.

Additional symptoms such as a low grade fever and vomiting may also occur. These symptoms can be mistaken for a similar condition or illness, which is why diagnosis and treatment can be helpful. If treatment is not sought, symptoms can last for around one month before dissipating. They can also return in lesser severity after this period of time.


Cyclosporiasis results from an infection caused by a parasite called Cyclospora cayetanensis. This single cell protozoan can only transfer to a person through the ingestion of water or food that has been contaminated by feces. In instances where outbreaks have occurred in the US and Canada, several imported foods have been linked to this illness, including raspberries, lettuce, and fresh basil.

While many infections from contaminated food can be caused due to restaurant workers touching food with unwashed hands, this is not the case with this infection because the parasite doesn't become infectious until a lengthy period of time after having passed through the bowel movement.

Diagnosis & Tests

Due to the fact that symptoms of this condition can be caused by a myriad of issues, blood tests are unable to directly identify if this illness is affecting the patient. Testing for this condition also isn't automatically administered when a person is experiencing constant diarrhea. Diagnosis can occur by examining the patient's stool sample for signs of the parasite.

Because of the possibility that enough of the parasite won't shed into the sample, making it undetectable when the test takes place, the initial test may not be enough to determine whether or not the illness has been contracted. In order to safeguard against this, many doctors will take stool samples over a period of several days. The samples that are taken are placed under an ultraviolet fluorescent microscope, as the Cyclospora oocysts are readily auto-fluorescent, and shine brightly under these microscopes.

Treatment & Therapy

If Cyclosporiasis has been diagnosed, there are several available treatment methods. The only antibiotic available currently is a combination drug known as trimethoprim/sulfamethoxazole. This drug is a standard treatment that should clear the infection in a matter of a few days to a little over a week. Patients will also be advised to drink lots of water in order to replace the fluids lost from the diarrhea.

The vast majority of people with healthy immune systems should be able to withstand the effects of the infection, even without antibiotics. If these treatment methods don't work, the illness can continue for anywhere from a couple of days to around a month or so. The illness lasts longer for anyone that is in poor health already.

Prevention & Prophylaxis

To prevent this infection from occurring in the first place, people should be careful with the foods they eat or beverages they drink, especially when traveling in a foreign country. It is wise to check the FDA's website on an occasional basis to see if any foods marketed in the US have recently been linked to an outbreak.