After a notably dry summer followed by wetter-than-average autumn conditions, the UK livestock industry is facing a critical rise in liver fluke infections among sheep and cattle. This parasitic disease, caused by Fasciola hepatica, is not only a threat to animal welfare but also a growing economic burden, with estimates suggesting it costs the UK farming sector up to £300 million annually.
What Is Liver Fluke?
Liver fluke is a parasitic flatworm that infects the liver of grazing animals. Its complex life cycle involves an intermediate host — the mud snail Galba truncatula — which thrives in wet, poorly drained pastures. Once ingested by livestock, the immature flukes migrate through the liver, causing tissue damage, inflammation, and in severe cases, death.
Why the Sudden Surge?
Despite the dry summer of 2025, the wet and warm conditions that we are seeing in early Autumn is creating ideal conditions for snail proliferation and fluke development. The Ollerenshaw index, a forecasting tool used to predict fluke risk, exceeded 400 in monitored sites — a clear indicator of high infection risk.
This paradox — dry summer followed by wet autumn — has extended the fluke season, with cases now appearing later into winter and even spring. Experts warn that traditional treatment timings may no longer be effective, leaving livestock vulnerable.
7 Alarming Signs of Liver Fluke Infection
- Sudden Death in Sheep – Acute liver fluke can cause rapid death due to massive liver damage.
- Distended Abdomen & Anaemia – Severe infections often present with painful swelling and pale mucous membranes.
- Bottle Jaw – A classic sign of chronic fluke, this swelling under the jaw is due to protein loss.
- Reduced Appetite – Infected animals may show signs of lethargy and poor feed intake.
- Weight Loss & Poor Growth – Chronic infections hinder productivity and growth rates.
- Milk Yield Reduction – Dairy cattle may produce 5–15% less milk.
- Increased Susceptibility to Other Diseases – Liver damage can predispose animals to clostridial infections like Black Disease.
The Hidden Danger of Routine Treatments
Many farmers rely on routine flukicide treatments in autumn, but experts caution that these may be mistimed. Flukicides often lack residual activity, meaning livestock re-exposed to infected pastures remain unprotected. Treating too early can leave animals vulnerable during the peak infection window in late winter and early spring.
Testing Is Key
The mantra “Test, don’t guess” is more relevant than ever. Faecal egg counts and coproantigen tests are vital tools for diagnosing liver fluke and assessing treatment efficacy, both of which we can assist with here at Dyfed Farm Vets. Testing helps avoid unnecessary treatments, reduces drug resistance, and ensures timely intervention.
Climate Change and Resistance: A Double Threat
Climate variability is reshaping the epidemiology of liver fluke. Milder winters and unpredictable rainfall patterns mean snail habitats are more widespread, and fluke development continues year-round. Compounding the issue is growing resistance to triclabendazole, the most effective flukicide, making sustainable parasite control more challenging.
What You Can Do Now
- Monitor Pasture Conditions: Identify wet, poorly drained areas and limit grazing.
- Implement Strategic Testing: Use faecal egg counts and coproantigen tests regularly.
- Review Treatment Protocols: Ask us how to adjust timing and product choice and what the options are.
- Vaccinate Against Secondary Infections: Protect against clostridial diseases like Black Disease.
- Educate and Collaborate: If you are ever in doubt please give us a call or come and see us in practice. There are platforms such as SCOPS and COWS which offer resources and podcasts to stay informed.
Final Thoughts
The rise in liver fluke infections is a serious wake-up call for us as vets, our clients, and all UK livestock producers. With changing weather patterns and evolving parasite behaviour, traditional approaches are no longer enough. By embracing testing, adapting treatment strategies, and staying informed, you can protect your herds and flocks — and safeguard your livelihoods.
To discuss any treatment plans, learn about the tests that we offer in practice or to answer any questions please give us a call on 01267 220404 or 01994 230220 or pop into practice.
