Clinical Presentation

The most typical clinical presentation in humans in gastroenteritis, or watery diarrhea, because Cyclospora infects the small intestine, most notably in the jejunum. Other symptoms can include the loss of appetite, substantial weightloss, bloating, increased flatus, stomach cramps, nausea, vomiting, muscle aches, low-grade fever and fatigue. In the large outbreak due to contaminated raspberries in 1996, the four most common symptoms were diarrhea, anorexia, fatigue and weight loss.
Untreated infections typically last for 10-12 weeks and may follow a relapsing course. Some infected persons may be asymptomatic. Cyclosporiensis is not typically life-threatening, and despite the cartoon above, it is not a trivial illness either. The frequent bowel movements and substantial weight loss can result in persistent fatigue and problems with nutrient absorption. Also, in immuno-comprimised patients, cyclosporiensis can lead to Reiter’s syndrome and potentially Guillain-Barr syndrome.
Sporulated Oocyst	Unsporulated Oocyst
Patients typically shed oocysts (the noninfectious form of the parasite) while the symptoms persist. The resolution of the disease symptoms usually corresponds to the cessation of the excretion of the oocysts. However, it has been documented that some patients in Nepal continued to shed oocysts for up to a month after treatment.
Because the sporozoites (the infective form of the parasite) invade cells along the small intestine, the illness can cause histologic abnormalities in the intestine. These abnormalities include inflammation, disruption of surface epithelium, and crypt hyperplasia. It is possible to be reinfected by the parasite, although the illness is less common in persons with repeated exposure. As a result, children in developing countries have relatively mild symptoms or are totally asymptomatic. However, in adults with no exposure to the parasite (e.g. upper and middle class adults in Peru and the U.S., and travelers to Nepal), the illness is usually much more severe.