Detection of the fluke infection status of on farm snail habitats as a tool to manage liver fluke

The project set out to provide information to participating landowners on the infection status of on farm fluke snail habitats by conducting surveys for Galba truncatula ‘fluke snails’ whilst developing an environmental DNA (eDNA) assay to detect their presence in water from the habitats. All the farms were visited between 2-4 times and between 4 and 9 wet habitats were repeatedly surveyed on each farm during each visit. Water from the habitats was filtered through eDNA filters and snails were collected for DNA analysis. In addition, faeces from livestock grazing the fields surrounding the habitats were collected. During the course of the project we identified livestock groups with liver fluke and rumen fluke infection via faecal egg counting and by the end of the project we were able to determine whether fluke snails were likely to be present within habitats and whether liver fluke and rumen fluke DNA were also present. The presence of fluke snails is a clear risk factor for fluke infections in livestock as the snails are integral to the fluke’s lifecycle.

We were able to categorise the habitats into:

• habitats where we could not detect fluke snails
• habitats where we observed fluke snails or we could detect fluke snail DNA in water but did not detect fluke DNA
• habitats where we observed either fluke snails or detected their DNA in water and detected fluke DNA either in the snails or water

We interpreted that habitats containing both snails and fluke were likely to have posed a fluke infection risk to livestock during the past grazing season and that this may continue into the next grazing season.

We interpreted that habitats with evidence of the presence of snails but no observed detection of fluke infections may have been less likely to have posed a major risk to livestock during the past grazing season, but that they may pose a risk in the next grazing season if they are infected by fluke eggs shed by livestock late in the grazing season.

We interpreted that habitats where we did not detect any traces of snails are less likely to have posed a risk to livestock during the past grazing and this lower risk is likely to continue at least in the early part of the next grazing season. However, if these habitats represent favourable habitats for snails they may become colonised by snails in the future.

We believe that the project was able to identify habitats that contained fluke snails and some of which were likely to be infected with fluke. Interventions to reduce contact between livestock and fluke metacercariae can be costly (fencing, draining) and being able to prioritise which habitats pose the most immediate risk should be valuable information to manage fluke risk in the future.