Scotland exposed to ‘very high’ liver fluke risk
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Chronic fluke in cattle
- Chronic weight loss
- Poor feed conversion efficiency
- More susceptible to other disease
- More than 20% of British cattle livers are condemned due to fluke damage each year
Mild weather has allowed liver fluke to survive on pasture to an abnormal level through the winter, with farms in Scotland at particularly high risk, warn animal health experts.
Testing and treating suspected sheep and cattle can minimise production losses, advises livestock veterinarian Peers Davies in February’s Nadis outlook.
This warning follows three months of “massively higher” rainfall and temperatures, which has increased pasture survival of parasites. The risk is particular ramped up in western and northern regions.
“Normally we expect levels of infectious pressure on pasture to drop as metacercariae are killed by freezing conditions,” explains Mr Davies. “Less cold weather across most of the UK means we are seeing higher infection levels at pasture than normally expected.
Mr Davies advises Closantel and Nitroxynil products be used where there is a known liver fluke problem.
Treatment options
- Closantel/Nitroxynil are “very effective products” at killing late immature and adult fluke, but correct dosage must be followed
- Avoid Triclabendazole in February as this will drive development of resistance, meaning nothing is available to treat in autumn
Testing options
- Copra-antigen ELISA test – will detect fluke in faeces slightly earlier than FEC
- Faecal Egg Count (FEC) test
- Select animals showing symptoms, for example thin ewes
- Group and sample animals appropriately – a veterinarian could advise on sample sizes
But he adds: “These products have a relatively low therapeutic index, so we must be careful that we are dosing correctly, as excessive overdosing can be fatal and underdosing means products aren’t effective.”
Chronic liver fluke will be the “predominant form” of the disease across the UK, although outbreaks of acute fluke have been seen as late as February.
“Chronic cases are now typically seen in cattle and sheep that have ingested low to moderate numbers of parasites that are now developing into final adult form and starting to exert pressure on hosts,” adds Mr Davies.
Effects are most stark in sheep, where early embryonic loss and a reduction in lambing percentages can hit farm profits.
Farmers are also advised that bottlejaw is a rare presentation with chronic fluke and that this symptom should not be relied on alone to diagnose flocks.
Sioned Timothy, veterinary adviser for Merial Animal Health, says: “Chronic fluke infections can put a lot of strain on pregnant ewes. If untreated, these animals may lose a significant amount of weight, and in severe cases both the lambs and the ewe may be lost.
“Outwintered cattle are at particular risk due to the relatively mild winter weather, which allowed infective fluke to remain active on the pasture long into winter. Cattle grazing potentially infected pastures should either be dosed or checked for the presence of fluke eggs in faeces.”