About Liver Fluke
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.
Life cycle of Fasciola hepatica has been kindly shared with us by Dr Clive Bennett (University of Southampton, rtd) and film maker Dr David Barlow.
Fluke and roundworm FEC shows how Moredun scientists look for the parasite.
Flight the Fluke introduces you to liver fluke, as well as how to prevent it from spreading.
Test Don’t Guess takes you through easy steps to monitor infections levels and assess anthelmintic efficacy in roundworm and liver fluke in your sheep and cattle.
Stop the Creeps on Sheep is a fun way to learn about the four main ectoparasites of sheep, which treatments are effective and how to use them for best effect.
- 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.
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
Counting snails – not sheep – may hold answers for fluke and wading birds.
It is well known that liming can improve forage production but the wider effects of liming are poorly understood. A liming research project is underway at the Game & Wildlife Scottish Demonstration Farm (GWSDF) Auchnerran on Deeside which now incorporates studies being run by both Moredun Research Institute and the James Hutton Institute.
The liming of fields is being used to help with a Moredun Research Institute study into liver fluke infection in grazing livestock. The Moredun researchers are interested in whether numbers of mud snails are affected by liming – something that, surprisingly, we don’t know much about. Mud snails are an intermediate host for liver fluke, a highly pathogenic flatworm parasite of grazing livestock. Where fluke is present it will often be found in the snails, although there may be snails present and no fluke.
This work is increasingly relevant as some agri-environment prescriptions promote boggy and wet ground. Some resistance to taking up these options can come from livestock farmers perceiving risks from fluke infection that outweigh the benefits that these habitats can have for wildlife. These studies are a part of a combined package of work to look in more detail at how great those risks may be.
The research at GWSDF Auchnerran is monitoring two fields with half their area limed and half not limed. GWCT has identified 10 sites (each up to one metre radius) in each field, five limed and five un-limed. At each of these, a 10 minute search for snails will be conducted up to once a month between April and October when the snails are on the surface. The snails found will be counted and sent to the Moredun where they will be identified to species level and screened for fluke infection.
The first counts are being done now before the lime is applied. Game & Wildlife Conservation Trust (GWCT) is also conducting a further mud snail survey at a number of other sites as a separate project.
The James Hutton’s liming research, also underway on a number of other farms across Scotland, aims to look at the effects of liming on soil chemistry, invertebrate biodiversity and sward composition. GWSDF Auchnerran, is particularly interested in how liming affects soil invertebrates as these provide a valuable food source for wader species.
Dr Dave Parish, Head of Scottish Lowland Research, GWCT says: “GWSDF Auchnerran is an ideal location for these projects, not least because we run a 1200 ewe sheep flock there so fluke is a major concern. And our ongoing work with waders is another area of considerable interest, and whether liming can provide a better environment for their breeding success.”
Dr Philip Skuce, Principal Scientist at the Moredun Research Institute, says: “Liver fluke risk is a genuine concern for livestock farmers and we know fluke has been a problem on GWSDF Auchnerran in the past. This collaboration with GWCT and the James Hutton Institute provides a unique opportunity to investigate the actual fluke risk associated with the implementation of agri-environment options and we look forward to working together over the coming weeks and months.”