Liver Fluke

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The liver fluke, Fasciola hepatica, is a highly pathogenic flatworm parasite of ruminants, mainly sheep and cattle. It causes severe liver damage, especially in sheep and can result in the sudden death of previously healthy animals. The disease is also responsible for considerable economic losses, estimated at ~£50m in Scotland alone, due to direct production losses, poor reproductive performance and livers condemned at slaughter. The disease appears to be on the increase in the UK and spreading into previously fluke-free areas, possibly as a result of recent climate change (milder winters and wetter summers) favouring the parasite and its mud snail intermediate host.

Control of fluke has historically involved the strategic application of flukicidal drugs, however, this approach is not thought to be sustainable in the face of increasing reports of flukicide resistance. Diagnosis of fluke is also not straightforward. Faecal egg counting is not a reliable indicator of infection and immunological tests do not discriminate between current and previous infections. Also, there is no vaccine available against fluke.

​NADIS publishes a monthly Parasite Forecast for farmers and livestock keepers, based on detailed Met Office data. The Parasite Forecast outlines the parasitic challenge facing cattle and sheep in the different UK regions.

Key Points

  • Liver fluke has a complicated life-cycle involving a tiny mud snail intermediate host which is responsible for infection on pasture. Weather patterns and ground conditions that favour the snail typically also favour fluke transmission and increase fluke risk.
  • Cattle can be a significant source of infection on farms with mixed grazing so sheep and cattle should therefore be included in any fluke control programme.
  • A sustainable fluke control programme should include diagnostics, management options such as drainage, fencing and housing, in conjunction with strategic flukicide treatment if necessary.
  • It is important to remember that not all anthelmintics kill fluke and not all flukicides kill all stages of fluke. Also, most broad spectrum 'wormers' do not kill fluke.
  • It is vitally important to use the most appropriate flukicide for the life-cycle stage (and species) of fluke most likely, or confirmed, to be responsible for disease in your animals at the time.
  • As with any anthelmintic treatment, care should be taken to dose animals accurately, according to the manufacturer's recommendations and, if possible, treatment should be followed up by an assessment of how well that treatment has worked. A post drench check or, better still, a faecal egg count reduction test using samples taken before and after treatment are the most practical options at present.
  • Always consider fluke biosecurity when buying in stock/or returning outwintered stock. You do not want to bring fluke onto a farm that is fluke-free or, worse still, bring resistant fluke onto your own farm.
  • We have recently seen the emergence of another fluke parasite, rumen (or stomach) fluke. Rumen fluke infection may be becoming increasingly common but clinical disease is still very rare at this time and there is very little scientific evidence of physical damage or production effects caused by rumen fluke.
  • The fluke situation is ever-changing. Assess the fluke risk on your farm and make best use of all available information to assist with fluke control such as abattoir returns, post mortem results, diagnostic test results, regional fluke forecasts, farm history and the experience of your local vet to plan a customised fluke control strategy, tailored to the fluke situation on your farm.

Research at Moredun

Here at Moredun, we have recently initiated research aimed at:

  • Improving diagnosis of active fluke infection in the host animal through an evaluation of existing blood and faecal fluke ELISA tests
  • Determining the efficacy of flukicidal treatment as a measure of emerging resistance
  • Monitoring fluke infection levels on farm as a predictor of disease risk, by measuring intermediate host snail abundance and fluke infection levels over the grazing season
  • Identifying novel vaccine targets on the surface of the fluke gut – this approach has been particularly successful against blood-feeding parasites such as Haemonchus contortus; F.hepatica is also a blood-feeder

Farming and Veterinary Outreach

For further Information about Liver Fluke please see Moredun Newssheet 6.16 - Fighting Fluke in Sheep and Cattle: