Sheep Liver Fluke

• GeneralIt needs a freshwater snail to complete its cycle before it can infect livestock.
• parasitismoIt completes a complex life cycle that needs a freshwater snail as an intermediate host before it can infect its final host, usually a grazing mammal.
• The metacercariae encyst on watercress and other bankside plants, and human infection almost always comes from eating raw wild watercress.
• A single adult parasite can live for years in the bile ducts and lay tens of thousands of eggs a day.
• It is one of the main causes of economic loss in sheep and cattle farming in wet regions.
• Its cycle must pass through a freshwater snail, in which the larvae multiply asexually: a single egg can yield hundreds of infective larvae.
• Those larvae leave the snail, encyst on aquatic vegetation and wait. Infection happens on eating wild watercress or drinking water containing those plants.
• Once swallowed, it passes through the intestinal wall, crosses the abdominal cavity and bores through the liver until it reaches the bile ducts, where it settles.
• In livestock farming it causes enormous losses through condemned livers and reduced production.
• The WHO classes it as a neglected tropical disease; in the highlands of Bolivia and Peru there are foci with very high human prevalence.

Skeleton type

Invertebrate - no rigid skeleton (hydrostatic skeleton)

Habitat and environment

A parasite: the liver of sheep, cattle and people; ponds and damp meadows

Sources consulted: Wikipedia (es): Fasciola hepatica