E. multilocularis is found primarily in subarctic and arctic regions in North America,Europe, and Asia. The adult worms are found in the gut of foxes and, to a lesser extent, coyotes. Their larval forms find harborage in the tissues of mice and voles, the canines’ rodent prey. Domestic dogs may acquire adult tapeworms by killing and ingesting these larval-infected sylvatic rodents. Humans are infected with larval forms through the inges-tion of eggs passed in the feces of their domestic dogs or ingestion of egg-contaminated vegetation. Unlike the larval forms of E. granulosis, those of E. multilocularis bud exter-nally, producing proliferative, multilocular cysts that slowly but progressively invade and destroy the affected organs and adjacent tissues.
The clinical course in humans is characterized by epigastric pain; obstructive jaun-dice; and, less frequently, metastasis to the lung and brain, thus closely mimicking a hep-atoma. Serologic tests are usually positive. Combined drug and surgical treatment often slows the progress of the disease and relieves symptoms. It is seldom curative.