New mud snail DNA test is combating liver fluke risk on Welsh farms

The presence of mud snails is a clear risk factor for fluke infections in livestock
The presence of mud snails is a clear risk factor for fluke infections in livestock

A new technique which identifies the presence of mud snails by detecting their DNA is being used to help farms identify habitats with the greatest potential to infect livestock.

The presence of mud snails is a risk factor for fluke infections in livestock as the snails are integral to the fluke’s lifecycle.

But detecting these snails, which are not present in all wet areas as commonly assumed, is not easy.

Trained staff are needed to identify potentially suitable habitats, find these tiny, elusive creatures and differentiate them from other non-fluke transmitting snails.

During a joint project between the Welsh government's Farming Connect and the Institute of Biological, Environmental and Rural Sciences (IBERS) at Aberystwyth University, potential mud snail habitats were surveyed on five farms across Wales.

Dr Hefin Williams, a lecturer in agricultural environment at IBERS, who led the study, says this process would be impractical on a national scale because it is costly and time consuming, but an environmental DNA test developed at Aberystwyth University could be the solution.

During the trial, that test identified mud snail DNA in each habitat where snails were physically detected and in other habitats where no snails were seen.

“The test also picked up both liver fluke and rumen fluke DNA in mud snail habitats which is also promising as we look to develop this test further in future and use it to assess fluke infection risk in fields,” says Dr Williams.

DNA-capturing

The five farms – one dairy and four beef and sheep - were visited up to four times between May and October 2017, when wet habitats were repeatedly surveyed.

Water from the habitats was filtered through DNA-capturing filters which were then screened for the presence of mud snail, liver fluke and rumen fluke DNA.

Dr Rhys Jones, who was involved in the research during his PhD, says livestock groups infected with liver fluke and rumen fluke were identified using faecal egg counting.

“By the end of the project we were able to determine whether mud snails were likely to be present within habitats and identify their fluke infection status via DNA analysis.”

Each of the farms was given a detailed map assessing fluke infection risk in each area.

“It’s hoped that these maps will assist farmers in making informed livestock management decisions in consultation with their vet to assist with fluke control,” says Dr Jones.

“Interventions to reduce contact between livestock and fluke on pasture such as fencing and draining can be costly and being able to specify and prioritise which habitats pose the most immediate risk should be valuable information to manage fluke risk in the future, especially as the threat of anthelmintic resistance grows.”

Fluke prevalence

The study comes two years after a team from IBERS published research on the prevalence of rumen fluke on Welsh farms.

That study found that 61 per cent of farms sampled were positive for rumen fluke, 68% were positive for liver fluke and co-infection of both flukes was seen on 46% of farms. Only 17% were negative for both.

Of the five farms involved in the latest research, some have since fenced off newly identified mud snail habitat from livestock as well as adapting their fluke control programme to test livestock in the spring to ensure that animals shedding fluke eggs onto mud snail habitats are identified via FEC testing and treated.