Atlas of livestock parasites
digitized collection of microscopical preparations

Atlas of Parasites Contents Information sources Glossary Administration

Tapeworms (Cestodes)



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Tapeworms live in the intestinal tracts of their hosts. Adult tapeworms cause little damage to their hosts beyond robbing the host of some micronutrients, such as vitamins. Adult tapeworms are visible to the naked eye and range in size from 0.04 inches to 50 feet long. An infection of tapeworms is called cestodosis. 

Adult tapeworms are found in the intestinal tracts of their definitive, or final, hosts. Each adult tapeworm consists of a head (scolex), which attaches the tapeworm to the intestinal wall, neck, and various numbers of segments, developing from the neck region. As new segments are formed at the neck, older segments are pushed back. Tapeworms are hermaphroditic; each segment has two sets of male and female reproductive organs, which will fill the segment with fertile eggs as the segment is pushed back from the neck. When the segment is full of eggs, it detaches itself from the adult tapeworm and is passed in the feces. Each genus and species of tapeworm has at least one intermediate host, which ingests the tapeworm eggs.

After the eggs hatch, the immature tapeworms migrate out of the intestine of the intermediate host and travel to various tissues in the body, depending on the genus of tapeworm. The immature tapeworm enters tissue in the intermediate host and is enclosed in a cyst, in which young tapeworms develop to an infective stage. Definitive hosts are infected by eating the cystic tissues of intermediate hosts infected with immature tapeworms.

There are three tapeworms of zoonotic importance: Dipylidium caninum, Diphyllobothrium latum, and Echinococcus spp.


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