WEATHER PATTERNS affecting the life cycle of liver fluke indicate that this should not be a high risk year for it, but clinical and sub-clinical disease have recently been reported in low risk areas.
There is some debate over whether more cases of fluke, which can affect cattle and sheep, are being seen in previous low risk areas. Graham David of the Vet Lab Agency, Shrewsbury, says fluke is generally still being seen where expected in the west.
“We have seen no real increase in long-term infection levels in other areas of England and Wales.” Recent cases are more likely to come from local environmental conditions, than a long-term pattern, he reckons.
Clinical cases have not yet been found in young animals in south of England abattoir surveys, says Bristol Vet School’s Gerald Coles. But flukes are being found in over 30-month cattle and are in the deer population. “Liver flukes are sitting and waiting in the south,” he warns.
But Neil Sargison of the Royal Dick Vet School, Edinburgh, reports recent cases in eastern parts of the UK, where infection levels have previously been low. His practice has diagnosed four cases in the past two weeks, with both clinical and sub-clinical cases. These sub-clinical cases are difficult to spot early on, says Mr Sargison. “Yet, they can cause death in young sheep not previously exposed to infection.”
One of the cases involved early lambing ewes with 20% barren at scanning. “This is much higher than normal and prompted the owner to seek vet advice.”
Blood samples revealed no sign of toxoplasmosis or Border disease, but further tests revealed low levels of two blood proteins, indicating an inflammatory process in the liver.
“Some ewes also had high worm egg counts, at 350/g of faeces and two had a few liver fluke eggs. However, as it was a sub-acute infection, numbers of fluke eggs were low and difficult to find.”
Although it has not been a high risk year for fluke, producers should still be aware of it this winter, he warns. “It’s difficult to advise against treatment, but checking faecal samples may be worthwhile first.
Blood sampling for protein levels is probably the best diagnosis of sub-acute cases and is worth considering when there is a trigger factor, such as high numbers of barren ewes at scanning.
Where fluke is detected, Mr Sargison recommends using a triclabenzinol-based flukicide, which kills early immature fluke. “However, there is some resistance developing to these products. “Where this is the case, aim to remove adult fluke in May with other products and consider management aspects of fluke control, such as field drainage.”
A point echoed by SAC vet Brian Hosie. “Over the past 10 years priorities have changed leaving maintenance tasks, such as drain clearance, to suffer.”
Many also forget the danger liver fluke poses to cattle, reckons Dr Hosie.
And when fluke takes hold it can also lead to other problems, he warns. “The damage fluke causes to livers can allow clostridial diseases to thrive and lead to higher losses than fluke itself would do.”