Climate change is shifting liver fluke risk in sheep to later in the season

LONDON, UNITED KINGDOM – 2 November 2026. Climate change is shifting liver fluke risk in sheep to new geographical areas and to later in the season and farmers are now being advised to test for the parasite. 

This summer’s drought caused the mud snails that carry the liver fluke parasite to ‘wait out’ the dry weather and the subsequent wet and warm autumnal weather has now created perfect conditions for mud snails which carry the parasite to contaminate pasture. 

Mud snails thrive in damp, muddy environments such as ditches, boggy ground, the edges of ponds and slow-moving streams, so farmers are also being warned to keep livestock away from these areas to prevent sheep from migrating to the damp areas which would maximise exposure to liver fluke. 

While historically liver fluke is more prevalent in the wetter western and upland regions of the UK including Wales, Scotland, western England and Northern Ireland, slaughterhouse condemnations and laboratory surveillance is indicating that it is now being seen in areas previously unaffected by fluke. 

Ally Ward, veterinary surgeon at Zoetis UK, comments: “Climate change is altering the geographical range and seasonality of liver fluke. While it normally affects sheep during wet and warm conditions over 10°C in mid-Autumn around October, it is affecting flocks later than usual this year.” 

Peter Baber, a sheep farmer from Devon, runs a 400-acre, 900-ewe sheep enterprise on two holdings on the edge of the Dartmoor National Park. Liver fluke has been a challenge for Peter over the years and is something that he tests for to help prevent losses as soon as he receives an alert from SCOPS (Sustainable Control of Parasites in Sheep) warning that liver fluke is being reported. 

He says: “Liver fluke is certainly on my radar and while I have a good understanding of parasitology and how to confidently control worms, liver fluke is a different story. Some years we don’t experience liver fluke, but some years certain groups of sheep are diagnosed, particularly the ones grazing on one of our holdings which is river floodplain and prone to flooding. 

“While liver fluke fatalities are normally low, it can lead to health and welfare concerns and financial losses. Therefore, as soon as we receive the SCOPS alert for liver fluke, we take faecal samples and send them away for a coproantigen test. The test detects the parasite as early as four to seven weeks post-infection, unlike traditional faecal egg counts which only become positive 10 to 12 weeks after infection. We also do a routine faecal egg count at the same time to test for Strongyles and Nematodirus. 

“Last year we had positive tests for liver fluke and worms and treated 300 sheep on the floodplain holding with CYDECTIN TriclaMox, a combination oral drench treatment containing moxidectin and triclabendazole that treats for both, including Haemonchus, which we also have on our farm. We then followed up with a coproantigen test six to eight weeks later which was negative for liver fluke and a post-drench faecal egg count for worms, which was also negative. 

“Preventative measures and treating sheep with a flukicide for liver fluke are critical components to a flock health plan, both for the health and welfare of a flock and to protect a farm from financial losses,” adds Ally Ward. 

For further information on CYDECTIN TriclaMox visit https://www.zoetis.co.uk/widgets/livestock-farming/sheep/easset_upload_file76941_250642_e.pdf.

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