Echinococcus is a genus of small tapeworms of the class Cestoda whose larval cysts cause hydatid disease, one of the most serious food- and water-borne parasitic infections. Infection in humans with Echinococcus granulosus may follow ingestion of water or vegetation contaminated with eggs shed in the faeces of infected dogs, with cysts developing slowly in the liver and lungs over years. Prevention centres on deworming dogs, hygienic slaughter practices that deny dogs access to infected offal, thorough washing of vegetables, and safe drinking water. Meat inspection identifies hydatid cysts in livestock organs, which must be condemned and disposed of so the parasite’s life cycle is broken.