Echinococcosis--an emerging parasite in the immigrant population.

Echinococcus tapeworms are parasites that infect dog species worldwide and occasionally are transmitted to humans. Infection occurs most commonly in persons who raise sheep or cattle, and who have contact with dogs. The tapeworm eggs are typically ingested during play with dogs or through consumption of garden vegetables or water contaminated by dog feces. The most common sites of tapeworm cyst formation within the body are the liver and lungs, although any internal organ or bone can be infected. The tapeworm infection is generally asymptomatic for 10 to 20 years, until the cyst grows large enough to cause problems. Untreated infection can be fatal. The possibility of this uncommon infection is most often considered when cysts are found on imaging studies of affected organs. Serologic testing has variable sensitivity, but it can be helpful. Surgical removal of cysts is the usual treatment, often with perioperative use of anthelmintic medication to prevent recurrence of disease caused by later growth of undetected daughter cysts.