[[Image:Fasciola hepatica adult.jpg|thumb|right|150px|''Fasciola hepatica'' adults from a horse - Castellà Veterinary Parasitology Universitat Autònoma de Barcelona]]
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The adult liver fluke, ''[[Fasciola hepatica]]'', lives in the bile ducts of a wide range of animals, including sheep, cattle, rabbits and, less often, horses. It can infect humans causing a painful abdominal disease. The intermediate host in the UK is a mud snail, ''Lymnaea truncatula''. It causes significant economic losses in western parts of the British Isles due to deaths, clinical and subclinical cattle disease confined mostly to the younger stock. Fasciolosis is a seasonal disease with more serious outbreaks occurring in some years than in others. A similar but slightly larger species, ''F. gigantica'', occurs in wetter tropical regions.