Cysticercoid of Hymenolepis nana. In humans, Hymenolepis nana has a direct life cycle, with the cysticercoids developing in the villi of the small intestine, and auto infection is possible. In rodents, the life cycle may be either direct or indirect, with flour beetles or fleas serving as intermediate hosts.
Taenia hydatigena cysticercus in a sheep liver. When an appropriate intermediate host (any wild or domestic ruminant) ingests the egg of Taenia hydatigena, the egg will hatch in the small intestine and the released oncosphere will reach the liver via the blood. The embryo then breaks out of the portal vessels and migrates through the liver, eventually leaving the liver as a cysticercus and attaching to the serosal surface of organs and mesentery to await ingestion by a canid.
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