Cyclosporiasis is an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis, a protozoan that infects the small intestine and leads to gastrointestinal symptoms ranging from mild discomfort to prolonged diarrhea. The disease is most commonly transmitted through the consumption of food or water contaminated with the parasite, particularly fresh fruits, vegetables, herbs, and untreated water supplies. Unlike many bacterial foodborne illnesses, Cyclospora requires time outside the human body to become infectious, meaning that direct person-to-person transmission is considered unlikely.
This unique aspect of the parasite’s life cycle makes environmental contamination a key factor in outbreaks, especially in areas with inadequate sanitation or where irrigation water becomes contaminated with human waste. Cyclosporiasis has been reported worldwide, but it is more frequently identified in tropical and subtropical regions where sanitation infrastructure may be limited. Travelers visiting endemic countries are at increased risk, although outbreaks have also occurred in developed nations due to imported intestinal parasite infection. Symptoms typically appear about one week after ingesting the parasite, though the incubation period can range from a few days to two weeks.
The hallmark symptom is watery diarrhea that can persist for several days or even weeks if left untreated. Other common symptoms include loss of appetite, weight loss, abdominal cramping, bloating, nausea, fatigue, low-grade fever, increased gas, and occasional vomiting. Some individuals may experience cycles of improvement followed by recurrence of symptoms, making the illness particularly frustrating. While healthy individuals often recover with appropriate treatment, the disease can be more severe in young children, older adults, and people with weakened immune systems, who may experience prolonged illness and dehydration.
Because the symptoms overlap with those of many other gastrointestinal infections, laboratory testing is essential for confirming the diagnosis. Standard stool examinations may not always detect Cyclospora, so healthcare providers often request specialized stool tests using modified acid-fast staining, ultraviolet fluorescence microscopy, or molecular diagnostic techniques such as polymerase chain reaction (PCR). Multiple stool samples collected over several days may improve the likelihood of detecting the parasite because it may not be shed consistently.