When freshly passed in stool (1), the oocyst is not infective. Therefore, direct fecal-oral transmission cannot occur; this differentiates Cyclospora from another important coccidian parasite, Cryptosporidium. In the environment (2), sporulation occurs after days or weeks at temperatures between 22° and 32°C, resulting in division of the sporont into two sporocysts, each containing two elongated sporozoites (3). Fresh produce and water can serve as vehicles for transmission (4), and the sporulated oocysts are ingested (in contaminated food or water) (5). The oocysts excyst in the gastrointestinal tract, freeing the sporozoites, which invade the epithelial cells of the small intestine (6). Inside the cells, they undergo asexual multiplication and sexual development to mature into oocysts, which will be shed in stool (7). The potential mechanisms of food and water contamination are still under investigation.
