tapeworm

An intestinal parasitic worm, adults of which are found in the intestine of vertebrates; the term is commonly restricted to members of the class Cestoidea. Tapeworms consist of a scolex, variously equipped with spined or sucking structures by which the worm is attached to the intestinal wall of the host, and strobila having several to many proglottids that lack a digestive tract at any stage of development. The ovum, entering the intestine of an appropriate intermediate host, hatches and the hexacanth penetrates the gut wall and develops into a specific larval form ( e.g., cysticercoid, cysticercus, hydatid, strobilocercus), which develops into an adult when the intermediate host is ingested by the proper final host. A three-host cycle with a swimming coracidium, procercoid and plerocercoid (sparganum) larva, and adult intestinal worm is found in aquatic life cycles, as in Diphyllobothrium latum (broad fish t.) and other pseudophyllid cestodes. Other important species of t. are Echinococcus granulosus (hydatid t.), Hymenolepis nana or H. nana var. fraterna (dwarf or dwarf mouse t.), Taenia saginata (beef, hookless, or unarmed t.), T. solium (armed, pork, or solitary t.), and Thysanosoma actinoides (fringed t. of sheep).

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tape·worm 'tāp-.wərm n any of the class Cestoda of flatworms that are parasitic as adults in the alimentary tract of vertebrates including humans and as larvae in a great variety of vertebrates and invertebrates, that typically consist of an attachment organ usu. with suckers, grooves, hooks, or other devices for adhering to the host's intestine followed by an undifferentiated growth region from which buds off a chain of segments of which the anterior members are little more than blocks of tissue, the median members have fully developed organs of both sexes, and the posterior members are degenerated to egg-filled sacs, that have no digestive system and absorb food through the body wall, and that have a nervous system consisting of ganglia and commissures in the scolex and longitudinal cords extending the length of the strobila called also cestode see BEEF TAPEWORM, CAT TAPEWORM, dog tapeworm, FISH TAPEWORM, fringed tapeworm, PORK TAPEWORM

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(cestode)

n.

any of a group of flatworms that have a long thin ribbon-like body and live as parasites in the intestines of humans and other vertebrates. The body of a tapeworm consists of a head (scolex), a short neck, and a strobila made up of a chain of separate segments (proglottides). Mature proglottides, full of eggs, are released from the free end of the worm and pass out in the host's stools. Eggs are then ingested by an intermediate host, in whose tissues the larval stages develop (see plerocercoid, cysticercus, hydatid). Humans are the primary hosts for some tapeworms (see taenia, Hymenolepis). However, other genera are also medically important (see Diphyllobothrium, Dipylidium, Echinococcus).

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tape·worm (tāpґwərm) any flatworm of the class Cestoidea; many are intestinal parasites. Those infecting humans are principally of the genera Taenia, Diphyllobothrium, Dipylidium, Echinococcus, and Hymenolepis. The eggs are ingested by the intermediate host and make their way into the tissues, where their larval stages are produced (see hydatid cyst, plerocercoid, and cysticercus). When a person or animal eats the flesh of one of these intermediate hosts, the larvae develop within the alimentary canal of this second (definitive) host and become adult tapeworms, which consist of an attachment organ, or scolex, an undifferentiated neck, and a strobila made up of a variable number of separate segments, or proglottids, each of which is hermaphroditic and produces eggs. Called also cestode.