The season for disease due to Liver Fluke in cattle and sheep has been shifting later, and 2024/5 is no exception warn SCOPS and COWS.
“Historically, we would have expected to see acute/sub-acute disease in grazing livestock during the autumn and early winter,” says Philip Skuce of Moredun. “However, in recent years, this has been slipping later and later, and in 2025, we are even hearing reports of acute disease in March. This means there are still significant infectious burdens on some infected pastures in early spring, which could catch some producers out.”
Rebecca Mearns, APHA, concurs:
“We’ve also seen evidence of immature liver fluke at post mortem in recent weeks. Farmers with livestock that are outwintered on pastures at risk of carrying liver fluke need to keep up their guard.”
Where traditionally all development was thought to stop over the winter months, milder, wetter winters may allow liver fluke and its mud snail intermediate host to remain active and continue developing. One infected snail can go on to produce potentially hundreds of infective cysts (metacercariae)*, producing a huge potential for the infectious stage of liver fluke on pasture when they pass out of the snail.
“Too many farmers are simply sticking to routine flukicide treatments in the autumn/ early winter,” says John Graham-Brown, Liverpool University. “Flukicides have no residual activity if sheep or cattle go back on to infected pastures they will not be protected.” The danger is that, given the later onset of the liver fluke challenge, treatments given too early leave livestock vulnerable to infection and disease in late winter and spring.
Keep Testing** and assess the risks to your stock is the main message from the experts.
In the spring, the most appropriate test to use for diagnosis is usually the Faecal Egg Count/ Detection method, with a positive result indicating there are adult fluke burdens present. Adult-stage infection is treatable with a number of adulticide products***. This will mitigate any damage these fluke can cause to the animal and also reduces the potential contamination of pastures in the spring and summer.
It is, however, important to note that in animals at-risk from acute disease caused by juvenile flukes egg counts may not be as useful.
“In the past, use of an adulticide in spring would have covered most situations. If livestock have been housed, or have been kept away from risk from infected pastures for 10 weeks or more (e.g. placed on forage crop), then you can be assured that any fluke they carry are old enough to be laying eggs. However, the shift to later fluke activity means farmers need to stand back and ask if their animals may have been infected (or reinfected) much more recently. If so, then the fluke they are carrying may not be mature enough to be laying eggs,’ says Rebecca Mearns. “In these cases, a negative FEC does not rule out the presence of immature parasites and the test should be repeated.”
Treatments
To avoid putting unnecessary pressure on some actives, farmers are urged to choose the product they use based on the maturity of the stage of liver fluke to be targeted. SCOPS and COWS advise talking to your Vet or SQP about the options and do not use a product in combination with a wormer unless you know that a worming treatment is required i.e. never ‘just in case’.