Echinococcus is a platyhelminth worm belonging to the Cestoda class. E. granulosus and E. multilocularis are the two species responsible of the hydatid disease, an infection that can affect humans and other intermediate hosts. The definitive host is dog, while sheep and cattle are intermediate hosts that get infected by ingesting contaminated feces. In humans the infection mainly spreads in the liver, but it can also affect lungs, spleen, peritoneum and other parts of the body. Echinococcus reaches humans by the ingestion of food containing the eggs of the parasite and, after digestion, the embryo arrives to the liver through lymphatic vessels or venous blood. The cyst is already visible in the liver three weeks after its arrival; the cyst contains hydatid fluid which highly stimulates the allergic reactions of the patient. The infection can be asymptomatic for many years; if symptoms appear they can vary depending on the size and location of the cysts. The mortality is between 2 and 4% in case of E. granulo us infections and between 52 and 94% in case of E. multilocularis infections, that can be reduced to 10% after specific pharmacological treatments and surgery.
The serological ELISA test permits a correct diagnosis in 90% of infections, even though a differential diagnosis between the two species is not possible.