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Echinococcosis, cystic

Hydatid disease

Echinococcus granulosus


The small tapeworm (length under 1 cm) of dogs and canids, Echinococcus granulosus, is the most common species of Echinococcus. Intermediate hosts include herbivores, sheep, cattle, pigs, horses and omnivore animals. After an accidental infection, humans man can also become an intermediate host, resulting in cystic hydatid disease. 


Life cycle of Echinococcus multilocularis / granulosus


Dogs and canids are definitive hosts for Echinococcus granulosus. Eggs are passed with the faeces. After per oral uptake of eggs by an intermediate host (e.g. sheep or cattle), the oncosphere emerges from the egg and invades tissues of the intermediate host, primarily the liver. There the development of hydatid cysts (a fluid-filled larval stage with an inner wall with multiple scolices) takes place. If the infected intermediate host is eaten by a carnivore, scolices evert in the intestine and grow to adult tapeworms.