Liver fluke In horses

Liver fluke

Liver Fluke (Fasciola hepatica) is a flat, leaf-like parasite found in the liver of grazing animals, most commonly sheep and cattle, however it can also infect horses. Temperature and moisture levels in the current and previous year have a major impact on fluke populations with animals kept in wetter, warmer locations being more at risk.

  • Eggs are passed onto the pasture by adult fluke
  • In damp, warm conditions the eggs will hatch to form larvae (miricidium) which can infect a mud snail.
  • The larvae will multiply inside the snail and leave in a tadpole like stage (cercaria) to encyst on the grass forming metacercaria.
  • The grazing animal will then ingest the cyst which becomes an immature fluke and tunnels into the liver.
  • The liver fluke becomes a mature adult in the bile ducts of the liver feeding on the animal’s blood. 8-10 weeks after infection the fluke will commence egg production.


  • Anaemia due to fluke feeding on the blood of the animal
  • Damage to the liver
  • Weight loss
  • Poorer growth rates in youngsters
  • Occasional diarrhoea


There are no drugs for liver fluke currently approved for use in horses. The only way to treat an infection is for medication to be prescribed off licence by a vet.

Shop for liver fluke test kits here