While the liver fluke risk remains low for much of the UK this season, livestock farmers are being told to keep their guard up again in what is becoming a less predictable parasite challenge.
Experts from the Sustainable Control of Parasites in Sheep (SCOPS) and Control of Cattle Parasites Sustainably (COWS) groups say this unpredictability means diagnostic testing is critical to make sure animals aren’t treated too soon, or unnecessarily, or miss a vital treatment.
John Graham Brown of Liverpool University speaks on behalf of both groups: “It is really important to repeat testing until the risk period is over. A negative test does not mean you can sit back and relax.
"Plan to repeat tests in three to four weeks’ time to make sure you don’t get caught out. Sheep are most likely to be seriously affected by acute liver fluke disease in the autumn and early winter, which means they are the priority for testing and also the best indicator of the presence of liver fluke on the farm.”
Matt Colston, a vet with Elanco Animal Health, says the recent change in weather, becoming wet and relatively mild in some areas, will favour the mud snail that is critical to the liver fluke lifecycle.
“This means we could see an increase in infection rates in the coming weeks. The mild weather has also meant that cattle have tended to stay out longer, potentially exposing them to more risk.”
Rebecca Mearns, Sheep Veterinary Society president, added that so far this season, she had seen positive results in tests on faeces in some areas.
But she said "many samples received have tested negative as the liver fluke stages in the cattle and sheep are not yet mature enough to be detected by these tests."
"I would also urge livestock farmers to take note of feedback on liver rejections from the abattoir and always investigate any deaths with a post-mortem examination to check for evidence of fluke in the liver.”
This is echoed by Michele Macrelli of APHA, where there has been a significant number of positive test results for farms in South Wales, underlining the regional variation in risk this year.
"There are a number of tests and means of monitoring liver fluke available to farmers," she said, "The most appropriate one to use varies according to the season, reflecting the maturity of the liver fluke at different times of year."
SCOPS and COWS say farmers should talk to their vet or adviser about the test that is best for them, and which class of stock will give them the most useful information.