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DictionarySeeechinococcusEchinococcus Granulosus
Echinococcus Granulosus a tapeworm that in the adult stage parasitizes the intestines of dogs, wolves, jackals, and occasionally cats. The body measures 3–5 mm in length and consists of a scolex with four suckers and two crowns of hooks and three or four segments. The last segment, the only mature section, constitutes half the body length. The tapeworm’s eggs emerge from the host’s intestine with excrement and may remain on its fur. The intermediate host, which may be a cow, sheep, pig, or other animal, or a human being, becomes infested by swallowing the eggs. The larva (oncosphere) emerges from the egg while in the intestine of the intermediate host. It penetrates into the portal vein system through the intestinal wall and is carried by the blood to the liver or, in some cases, to the lungs, muscles, bones, and other organs, where it develops into a hydatid. Every oncosphere creates a cyst, and secondary and tertiary cysts form on its walls. Numerous scolices similar to those of adult worms form on the secondary and tertiary cysts. The cysts grow very slowly and become quite large. The definitive host becomes infected by eating the flesh of a diseased or dead animal and ingesting a worm in the hydatid stage. The varied structure of the hydatid stages of E. granulosus suggests there may be two independent species, E. unilocularis and E. multilocularis. The latter is sometimes recognized as an independent genus, Alveococcus. Echinococcus granulosus
Echinococcus [e-ki″no-kok´us] a genus of small tapeworms.Echinococcus granulo´sus a species parasitic in dogs and wolves and occasionally in cats; its larvae may develop in nearly all mammals, forming hydatid cysts in the liver, lungs, kidneys, and other organs. It reverses the usual process of development in human and animal hosts: the adult is found in the intestine of dogs, whereas the larva develops in the human intestine, penetrates the intestinal wall, and settles in various organs, most often the liver, where it forms a cyst (cyst" >hydatid cyst) that grows slowly. Treatment is by surgical removal of the cyst. This type of worm infection is fortunately not common in the United States.Echinococcus multilocula´ris a species whose adult forms usually parasitize the fox and wild rodents, although humans are sporadically infected. It resembles E. granulosus, but the larvae form alveolar or multilocular rather than unilocular cysts.E·chi·no·coc·cus gran·u·lo·'sushydatid tapeworm, a species in which adults infect canids and the larval form (osseous and unilocular hydatid cysts) infects sheep and other ruminants, pigs, and horses; may also occur in humans, giving rise to a large cyst in the liver or other organs and tissues. ECHINOCOCCUS GRANULOSUS CYSTSEchinococcus granulosusA species that infests dogs and other carnivores. Its hydatid (larva) develops in other mammals, including humans, and causes the formation of hydatid cysts in the liver or lungs. Synonym: dog tapeworm See: illustration; hydatidSee also: Echinococcus |