echinococcosis, formation of cysts, or hydatids, at the site of infestation by the larval form of Echinococcus granulosus, a tapeworm common in sheep, cattle, camels, dogs, and many other mammals. The disease can develop in humans upon ingestion of the eggs, which may be present in the tissues of infected animals or on food contaminated by their excreta. Echinococcosis occurs most frequently in Asia, the Middle East, the Mediterranean, and South America.
The emergent larvae become enveloped in a cyst that may grow for 5 to 20 years without being detected. Symptoms of infestation depend on the location of the cyst; common sites include the liver and the lungs. A cyst in the liver can cause weight loss, abdominal pain, and jaundice. Symptoms of a cyst in the lung may include coughing and chest pain. In rare instances the cyst may rupture, causing an anaphylactic reaction, which may be life-threatening.
Surgical excision of the cyst is the most effective treatment, but in many cases the disease recurs because the contents of the cyst may escape during the operation. When cysts occur in inoperable areas of the body, anthelmintic drugs, such as albendazole or mebendazole, may be used.