Liver Fluke

Liver fluke (Fasciola hepatica) is a parasite affecting cattle and sheep that can cause significant production losses and, in severe cases, death. It's a particular concern on wetter, low-lying land — which makes it an important consideration for many farms in our area.

Life cycle

  • Fluke eggs are passed in the dung of infected animals onto pasture.

  • They hatch and develop within mud snails, which thrive in wet conditions such as poorly drained pasture, ditches and marshy ground.

  • Infective larvae (metacercariae) are released from the snails onto pasture and surrounding vegetation, where grazing animals ingest them.

  • Once ingested, immature flukes migrate through the liver before maturing in the bile ducts, where they lay eggs to continue the cycle.

Because the life cycle depends on wet conditions and snail habitats, fluke risk varies significantly year to year depending on rainfall, and can vary considerably even between neighbouring farms.

Forms of disease

  • Acute fluke — caused by large numbers of immature flukes migrating through the liver simultaneously, typically in autumn; can cause sudden death, particularly in sheep, with little warning.

  • Subacute fluke — a slightly slower course, with weight loss, anaemia and reduced condition.

  • Chronic fluke — the most common presentation, caused by adult flukes in the bile ducts; leads to poor weight gain, reduced fertility, anaemia and bottle jaw (fluid swelling under the jaw) over weeks to months.

Signs to look out for

  • Sudden death (acute cases, particularly in sheep)

  • Weight loss or poor weight gain despite adequate feeding

  • Reduced milk yield

  • Anaemia — pale gums and inner eyelids

  • Bottle jaw (swelling under the jaw)

  • Reduced fertility and lambing/calving performance

  • General poor thrive in a group, sometimes only picked up at slaughter through liver condemnation

Diagnosis

  • Faecal egg testing, though this only detects adult fluke and can miss early/acute infection

  • Blood testing for fluke antibodies or liver enzymes

  • Coproantigen (ELISA) testing, which can detect infection earlier than traditional egg counts

  • Post-mortem or abattoir feedback, which often provides useful information on flock/herd-level exposure

Treatment and control

  • Several flukicide products are available, but they differ in which life stages (immature vs adult fluke) they treat — the right choice depends on the time of year and type of disease suspected.

  • Overuse or incorrect timing of flukicides contributes to resistance, so treatment should be targeted rather than routine.

  • Fencing off or draining high-risk wet areas can reduce snail habitat and exposure.

  • Testing before and after treatment helps confirm the product has worked and guides future control decisions.

Our approach

Because fluke risk varies by farm, season and rainfall, we recommend a tailored testing and treatment plan rather than a fixed annual routine. This helps target treatment appropriately, protect animal welfare and productivity, and reduce the risk of resistance developing.

Still have questions?

If you'd like to discuss a fluke testing and control plan for your farm, please contact us on 01797 252321.