Echinococcus granulosus is the
Human tapeworm that comes from dogs, as well as, other members of
the canidae family (foxes, coyotes, wolves, etc.) and cats. The
dog is the definitive host and passes the eggs of the adult Echinococcus
granulosus tapeworm through its stool. Sheep, cattle, goats, and
humans act as the intermediate host. Once the intermediate host
ingests the eggs, the eggs release the oncosphere (first-stage larvae);
the oncosphere then separates and invades the intestinal wall entering
the circulatory system. The oncosphere can travel throughout the
body and form parasitic tumors. The most common site of tumors from
the Echinococcus granulosus tapeworm is the liver (60%). These tumors,
formally called Hydatid disease, are also found in the lungs (25%),
brain, and other organs.
Infestation of the Echinococcus granulosus in humans is rare, but
the numbers are increasing due to the trapping and transporting
of wild coyotes, foxes, and wolves into states in which the parasite has not previously been found.