Liver fluke: when fields are wet matters, warn COWS and SCOPS

Cattle and sheep farmers are being urged by the Control of Worms Sustainably (COWS) and the Sustainable Control of Parasites in Sheep (SCOPS) groups to risk assess individual fields for liver fluke this autumn and winter.

It is also important to recognise when those fields were wet and whether wider conditions were suitable to allow the parasite to complete its life cycle, both crucial to understanding the threat.

Liver fluke risk increases when four key elements come together. Firstly, the liver fluke parasite must be present and suitable mud snails must be living nearby. There also needs to be sufficient moisture whilst average temperatures are above 10°C, to support snail activity and parasite development. Wet ground alone is not proof of infection and cooler weather does not mean pasture is free of infective cysts.

Professor Philip Skuce from Morden Research Institute, said: “The liver fluke forecast provides a useful regional starting point. The current liver fluke forecast indicates that risk varies across the UK, ranging from low in England and Wales to high in the north and west of Scotland, based on regional weather conditions during the spring and summer this year.

“That said, conditions can vary significantly between farms and even between fields. Combine the forecast with grazing history and diagnostic testing rather than assuming your animals are either safe or at risk.”

Dr Rhys Jones from Aberystwyth University added: “Although we often see the impact of liver fluke in our livestock during the winter, it is the summer months when wet conditions on pasture are most important for liver fluke to develop within their mud snail hosts. As such, areas of the UK that have experienced drought conditions this year are likely to have a very low risk of liver fluke, unless there are specific localised areas of pasture or features such as slow-moving streams that remained wet during the summer and early autumn.”

“Our research has demonstrated that risk assessing individual fields, including considering when those areas were wet, can help farmers better tailor their liver fluke control strategies.

“This is particularly important as risk can vary considerably between fields and between years, meaning different groups of animals may face very different levels of challenge depending on their grazing history.”

COWS and SCOPS advise farmers to review potential snail habitats, which are areas on pasture or edges of streams, ditches or ponds which contained at least some surface moisture for several weeks between late spring to early autumn, alongside farm history, test results and feedback from slaughter or post-mortem examinations.

Agree a testing plan with a vet, SQP or animal health adviser. Blood antibody, coproantigen and faecal egg tests answer different questions at different stages of infection, so a negative result is not an ‘all-clear’ for the season. Neither does treatment prevent fresh infection.

Flukicides only kill susceptible stages already present and provide no lasting protection, meaning animals can be reinfected if they return to contaminated pasture. Likewise, adult liver fluke found in older stock or carcases does not necessarily indicate recent infection. It is often the result of earlier infections surviving because treatments were mistimed or the chosen product was not active against the age of fluke present at treatment.

Different active ingredients kill different stages of liver fluke, so knowing which stages are likely to be present in the animal is essential when choosing an appropriate active. Discuss product choice, treatment timing and follow-up checks with a vet, SQP or animal health adviser, taking ongoing exposure into account.