Which of the following parasites is transmitted through the fecal-oral route?

Cyclospora cayetanensis is a protist responsible for causing cyclosporiasis, and it is transmitted through the fecal-oral route. This mode of transmission typically occurs via contaminated food or water. Cyclospora has a specific environmental resilience and can survive in damp conditions outside the host, making it more likely to contaminate fresh produce, especially when irrigation or handling involves contaminated water or feces.

In contrast, Plasmodium species, which cause malaria, are transmitted through the bite of infected female Anopheles mosquitoes rather than through fecal-oral routes. Strongyloides stercoralis, a parasitic roundworm, is primarily transmitted through direct skin contact with contaminated soil rather than via the fecal-oral route. Toxocara canis, the roundworm of dogs, is typically transmitted through ingestion of infective eggs shed in the feces of infected animals, but it does not fall under the classic fecal-oral transmission defined for other intestinal pathogens. Thus, Cyclospora cayetanensis is the clear choice for the parasite that is transmitted through the fecal-oral route.