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Figure 3.-Life Cycle of Echinococcus granulosus.
Structure
Adult Echinococcus granulosus tapeworms are relatively very small, consisting of 3 to 5
segments, and usually are less than 1 cm long. Dogs and wild canids are the only final hosts
in which the adults are found, often adhering in great numbers to the small intestinal
mucosa. The scolex has four suckers and is crowned with a circle of hooks as in Taenia
solium. It is followed by a germinative neck region, one developing segment, and usually
one gravid segment containing several hundred eggs (Figure 2 A, B).
Figure 2. A- Adult Echinococcus granulosus worm, B- scolex showing hooks, C-
hydatid brood capsule with protoscolices
The hydatid larva is found in sheep, in many other herbivores and in humans. In humans
the cyst is slow-growing, but in a period of years may reach a diameter of 30 cm with a 1
mm thick, laminated sheath surrounded by fibrous reactive host tissue. The cyst is usually
fluid-filled and, if viable, has a germinative inner lining from which many thousands of
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