BACKGROUND

Human infection with larval stages of tapeworms of the genus Echinococcus may take one of the three forms: unilocular hydatid disease caused by Echinococcus granulo-sus, multilocular or alveolar disease caused by Echinococcus multilocularis and polycystic hydatid disease caused by Echinococcus vogeli. Members of the dog family are defi ni-tive hosts for these minute tapeworms. Eggs are passed in the stools and ingested by the intermediate hosts, which include sheep, cattle, pigs, rodents and other herbivorous animals. Humans, especially children are infected. Following the accidental ingestion of eggs from envi-ronment, the eggs hatch in the intestine and the embryo penetrate the intestinal wall and then enter the blood stream. Although most hydatids develop in the liver, some disseminated to other sites. These may even reach th