The life cycle of Echinoccous granulosus begins when a sheep, swine, cattle, or other mammal ingests an embryonated egg (infective egg stage). The oncosphere (tapeworm embryo with hooks) then hatches and penetrates the intestinal wall of the host. This then forms into a hydatid cyst (a large cyst in which cells and daughter cysts begin to develop) in the viscera or soft tissues of the host. Protoscolices (juvenile scolex of Echinoccous granulosus tapeworm) can also bud from hydatid cysts. The infected viscera is then ingested by a carnivore. The scolex of the tapeworm protrudes from the cyst and attaches to the intestine of the new host. The tapeworm then forms into an adult in the small intestine, and its eggs come out in the feces of the host. If humans were to ingest an embryonated egg from the feces of a carnivoer, the oncosphere would hatch and penetrate the intestinal wall, allowing this tapeworm larvae into the circulatory system of the human host. Hydatid cysts then form in the liver, lungs, brain, etc. in the human host, and removal by surgery is required. Ruptured hydatid cysts are very dangerous and can cause death.
Echinococcus granulosus is not particularly virulent as a tapeworm, but the hydatid cysts that form as a result of ingestion of embryonated eggs can be lethal. These hydatid cysts house new protoscolices and hydatid sands, or the waste material of the protoscolices. These cysts can grow over years and hold several liters of fluid. The organs in the human host that these hydatid cysts are attached to experience massive levels of stress and this can lead to failure. If these hydatid cyst ruptures, anaphylactic shock can occur due to the immune system response to the rupture, the body can go into shock from the rupture, and death can occur. Symptoms can include abdominal pain, liver enlargement, hives, jaundice, eosinophilia, organ compression, infection, bile duct inflammation, blood vessel compression, and vitamin/mineral deficiencies.