Echinococcosis: Parasitic disease caused by the larval stage of the tapeworm Echinococcus. There are three forms of Echinococcus that affect humans -- E. (Echinococcus) granulosus, E. multilocularis, and E. vogeli -- and each has a different geographic distribution and tends to cause a different pattern of disease.

E. granulosus is common in areas where livestock is raised in association with dogs -- in Australia and New Zealand, Argentina and Chile, Africa, E. Europe, the Middle East, and the Mediterranean region, especially Lebanon and Greece -- and causes unilocular cysts.

E. multilocularis is found in Alpine, sub-Arctic, or Arctic regions -- including Canada, the United States, and central and northern Europe and Asia -- and causes multilocular lung disease known as alveolar hydatid disease (AHD).

E. vogeli is found only in Central and South America and causes polycystic hydatid disease.