This summer, a national initiative undertaken by XLVets and its member practices, will be tracking the advent of fluke risk on farms across the UK.
The initiative will also help alert farmers to when they should get their own livestock tested for exposure to fluke, and hence when or if to treat them with a flukicide.
Vet John Hemingway of Shropshire Farm Vets, who devised the study, explains: “Before treating any livestock for fluke, farmers should first assess whether the treatment is needed.
“The fluke’s lifecycle is dependent on the presence of mud snails.
“This infection risk begins each year when they come out of hibernation and conditions are warm and wet.
“However, the severity of the fluke burden in a given year is dependent on a combination of temperature, weather and the immediate environment.
“Theoretically, we might expect south west England and Wales to be the first areas to develop a liver fluke risk, then for the risk to spread north as the country warms up.
"However, every farm has its own micro-environment, micro-climate and stocking density.
“These farm factors also influence the advent of the risk and the level of fluke challenge.”
Mr Hemingway says, as a result, fluke treatment cannot be scheduled into a diary. Instead, it is best practice to test first and assess the risk. Treatment may not always be needed immediately.
“There is now a blood test for fluke which is very accurate and relatively cheap – about £50 to test six animals. It detects the presence of antibodies raised when an animal has encountered fluke. When this has happened, it is known as ‘seroconversion’.
"It can detect the presence of fluke from about two weeks after infection.”
This year, 30 XLVets practices are collaborating in a surveillance study which will track the spread of liver fluke through the UK, as temperatures rise.
Over three months, from July to September, a vet from each of the participating practices will be sending blood samples for analysis from lambs on farms with a history of liver fluke.
Mr Hemingway says: “These 30 farms are acting as disease sentinels, alerting us to the presence of liver fluke on that farm. If lambs have encountered liver fluke, their blood will have ‘seroconverted’.
“If lambs tested on a nearby farm have seroconverted, this does not mean all farms in the area need to start treating their livestock because the micro-environment and conditions differ, even between neighbouring farms. However, it does mean it is time to seek advice from the farm’s suitably qualified person or vet.
“Ideally, farmers need to have blood tests carried out on their own stock, to provide the evidence on which treatment advice can be based. Faecal egg counts can also be used, but these have limited use in detecting early infections.”
He adds: “An even cheaper test than the blood test is the faecal copro-antigen test which detects enzymes produced by fluke in the muck of infected sheep; it gives comparable accuracy and works out cheaper, as farmers can collect the samples themselves instead of needing a vet. It also allows a slightly earlier detection of fluke compared to egg counts.
“Even with a positive test result for fluke, farmers may be advised to wait a while before treating livestock, as part of a strategic control plan.”
SAFEGUARDING FLUKICIDE EFFICACIES
VET John Hemingway says: “In the treatment of liver fluke, only the active ingredient triclabendazole can kill all the life stages of the parasite. But in some parts of the country there is now firm evidence that resistance to this flukicide has developed.
“If we get really widespread resistance to triclabendazole, it puts us in a very difficult position.
“From a treatment perspective, there will be far less we can do to prevent the substantial damages caused by fluke: liver condemnation in abattoirs, lamb deaths in acute cases and loss of performance in chronically affected sheep and cattle.
“So to preserve the efficacy of all flukicides and, in particular, triclabendazole, it is imperative that treatments are only given when needed, and that products are selected and used strategically.
“This XLVets fluke sentinel initiative will track the advent of liver fluke risk through the UK this summer. We hope the results will encourage farmers to have their livestock tested to assess their risk before reaching for the fluke treatment – and to seek professional advice on selecting an appropriate flukicide.”