Giardia lamblia (Giardiasis). Infection occurs by ingestion of infective cysts, transmitted by food, water, feces, fomites, and flies. Excystation occurs in the small intestine, where the trophozoites multiply by binary fission, and cysts are passed in feces. Diagnosed by recovery/identification of trophozoites or cysts in feces or duodenal contents. Image from Pinterest, information from Medical Parasitology, A Self-Instructional Text.