Fasciolosis is acquired following the ingestion of vegetation or water contaminated with the encysted infectious liver fluke larvae, known as metacercariae. Metacercariae excyst in the intestines, burrow through the intestinal wall and migrate into the liver tissue where they spend about 8–12 weeks feeding on host tissue and blood and consequently causing extensive haemorrhaging and perforations. This acute stage of disease can result in death in highly infected sheep, but death is rarely seen in cattle. After this period the parasites move into the bile ducts where they complete their growth and maturation. The hermaphroditic adult liver flukes puncture the wall of the bile duct and feed on blood that provides the nutrient for the production of enormous numbers of eggs that are carried into the intestine with the bile fluids and are passed onto pasture with the faeces. An aquatic larval stage hatches from the eggs and infects an intermediate mud-snail host, such as Lymnaea truncatula. After several developmental and multiplication stages within the snail the parasites emerge and become encysted on vegetation and thus continue the cycle ( Andrews, 1999).