Infection by liver fluke, a type of flatworm, is a widespread parasitic disease present on all continents. Also known as fascioliasis, it affects the liver and bile ducts of a large variety of warm-blooded animals, domestic and wild, and humans, causing enlargement and thickening of the walls of the bile ducts and fibrosis of the liver tissue, resulting in loss of condition, digestive disorders, anaemia and other symptoms of parasitism. In sheep, extensive liver damage caused by flukes contributes directly to 'black disease', (infectious necrotic hepatitis), which does not occur in healthy animals. Economic losses arise from emaciation of domestic animals, and from production of liver unfit for human consumption.
Liver flukes infect over 17 million people worldwide causing marked morbidity and mortality.