The adult Echinococcus granulosus, which is about 3-6 mm in length, resides in the bowel of its definite host.
Gravid proglottids release eggs that are passed in the feces.
These eggs are then ingested by a suitable intermediate host, including sheep, goat, swine, cattle, horses and camels. The eggs then hatch in the bowels and release oncospheres that penetrate the intestinal wall. These oncospheres then migrate through the circulatory system to various organs of the host.
At the organ site, the oncosphere develops into a hydatid cyst. This cyst enlarges gradually, producing protoscolices and daughter cysts that fill the cyst interior.
These cyst-containing organs are then ingested by the definite host, causing infection. After ingestion, the protoscolices evaginate, producing protoscolexes.
The scolexes of the organisms attach to the intestine of the definite host and develop into adults in 32-80 days.
Humans can become infected if they ingest substances infected with Echinococcus eggs.
The eggs then release oncospheres in the small intestine.
At these places, oncospheres migrate through the circulatory system and produce hydatid cysts.
Larval stage develops both externally and internally, resulting in multiple vesicles.