Adult liver fluke (Fasciola hepatica) on the surface of a freshly-killed sheep liver. This parasitic flatworm is the cause of fascioliasis in humans and especially in sheep and cattle. Fascioliasis is a liver disease, causing digestive problems, fever, pain, anaemia and jaundice. It causes serious losses of livestock across the world, and is also thought to affect more than two million people. The flukes migrate to the liver after being ingested in contaminated water of food, in particular watercress. The adult forms live inside the liver, feeding on blood and liver cells. Its eggs are passed in faeces, and the fluke completes its life cycle as a parasite in freshwater snails. Filmed at Ridgeway Research, Gloucestershire, UK.