Fluke challenge continues to show variability

Parasite experts say the 2025-26 season is following the trend for variable extent and timing of liver fluke challenge.

Fluke challenge has been lower and later than traditionally expected in many parts of the country for several years now. 

However, John Graham-Brown of NADIS and the University of Liverpool says many farmers are sticking with traditional treatment windows, so a large proportion of treatments are being given too early. 

“This leaves livestock susceptible to disease, as the challenge typically increases through the autumn and into winter. There is no ‘insurance’ element associated with a fluke treatment given too soon,” he adds.

SRUC vet Heather Stevenson said Scotland is also seeing a much later start to the fluke season. 

“Last year, it was late in the autumn before we saw significant evidence of disease, even in some of our very high-risk areas. This is a long time after many traditional treatments had been given.”

APHA data also supports this trend for much later infections, Rebecca Mearns shares.

“We even had reports of acute disease due to immature fluke parasites in sheep in late winter/early spring in 2025. Farmers are often surprised that they have liver fluke issues because they treated stock earlier in the autumn. 

“The problem is that flukicides have no residual effect (or persistency), so if they put the stock back on to ‘flukey’ areas after treatment, they are as just as susceptible to a later challenge as untreated stock.”

The Sustainable Control of Parasites in Sheep (SCOPS) and Control of Cattle Parasites Sustainably (COWS) groups are urging farmers to use the testing available to decide if they need to treat, and when.

What can farmers do?

The key is to test, advises Philip Skuce of Moredun. “The first line of defence would be tests in the late summer and autumn that can detect early infection, from as little as two weeks after fluke are ingested off pasture.”

This involves either a blood test or the new lateral flow test which can be carried out on farm. 
“Both methods detect circulating antibodies to liver fluke and when used on this year’s first season grazing animals (lambs or calves), these animals can be used as ‘sentinels’ to identify if liver fluke is present in different management groups and/or parts of the farm,” he continues

Repeating the test every 3-4 weeks until it’s either positive or faecal methods can supersede this test, can also answer when to treat, avoiding unnecessary and costly treatments. 
Consideration also needs to be given to which flukicide would be most appropriate, given the likely age of liver fluke infection and age kill of the respective flukicides, and informed by testing,” he concludes.

Lesley Stubbings, of SCOPS, says it’s never been more important to test. 

Source: Farmers Guide