Echinococci are platyhelminths of the cestode genus. The parasitic cycle of the organism involves definitive hosts and intermediate hosts, each harboring different stages of the parasite life cycle. Carnivores are the definitive hosts for the adult form of the parasite, which is an intestinal worm, also termed taenia. Numerous (ie, tens to thousands) adult worms that average 2-5 mm in length live in the small bowel of carnivores (taeniasis) and are attached to the small bowel mucosa by hooks and suckers. After 25-40 days, the worm's last gravid segment, each containing hundreds of microscopic eggs (6-hooked oncospheres or hexacanth embryos, 30-40 mm in diameter), detaches from the nonfertile segments. The egg-containing segments are then dispersed through the feces of the carnivore. Like many other parasite infections, the course of Echinococcus infection is complex. Statistics: Only 2 cases involving humans living in this area were described in the 20th century. Transport of infected foxes from endemic areas to eastern and southern states for hunting purposes could create new areas at risk of becoming endemic. In Alaska, alveolar echinococcosis is observed in Eskimos, especially on St. Lawrence Island, where 30 of 53 cases were diagnosed in Alaska from 1947-1990. Recent studies in the United States and Canada suggest that the risk in humans is currently increasing in the two countries. Treatment: Many patients can be treated with anti-worm medicines. The cysts may be removed with surgery, if possible. But this can be a complicated surgery. Both cystic echinococcosis and alveolar echinococcosis are often expensive and complicated to treat, sometimes requiring extensive surgery and/or prolonged drug therapy.Four options exist for the treatment of cystic echinococcosis:percutaneous treatment of the hydatid cysts with the PAIR (Puncture, Aspiration, Injection, Re-aspiration) technique, surgery, anti-infective drug treatment, ?watch and wait?.