Walsh & Hoyt: Cestodes (Tapeworms)

Tapeworms are segmented helminths that cause illness in humans in either of the two stages of their life cycle: the adult stage, which causes signs and symptoms referable to the gastrointestinal (GI) tract, where the adult tapeworm resides, and the larval stage, which causes signs and symptoms secondary to enlarging larval cysts in various tissues of the mammalian host, including the eye and the brain. These worms have been recognized since the beginning of recorded history because of the impressive length of the adult (up to 30 feet) and because of the fluid-filled cysts in the larval state. Humans are the definitive host for some cestodes, such as Taenia solium, the cause of cysticercosis, whereas humans can only support the larval or intermediate stage of other cestodes, such as Echinococcus granulosus, the cause of echinococcosis.