Cyclospora oocysts are not sporulated (ie, infective) when passed in stool. Thus, direct fecal-oral transmission does not occur. 1. Unsporulated oocysts are excreted from the infected host in stool. 2–3. The oocysts sporulate in the environment after days or weeks at temperatures between 22 to 32° C. 4. The sporulated oocysts contaminate food or water. The mechanism for contamination has not been established. 5. The sporulated oocysts are ingested in contaminated food or water. 6. The oocysts excyst in the GI tract, releasing the sporozoites, which invade the epithelial cells of the small intestine. 7. Inside the cells, they multiply asexually and develop sexually to mature into oocysts, which are shed in stool.
Image from the Centers for Disease Control and Prevention Image Library.