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Mild Winter Increases Fluke Risk in UK Sheep, Cattle

10 February 2016

UK - There is a high risk chronic liver fluke burdens in livestock in western regions of the UK and especially in Scotland, according to the latest NADIS Parasite Forecast, sponsored by Merial Animal Health.

Beef and sheep farmers are warned to be on alert for signs of fluke disease and take appropriate action, based on local risk factors.

Chronic liver fluke infection peaks in the late winter and early spring. The recent mild weather has enabled a greater number of fluke to survive the winter, leading to high numbers of parasites on pasture.

Assessing and treating cattle and sheep now will help prevent production losses, particularly due to impaired reproductive performance in ewes, and increased finishing times for growing cattle. It will also reduce pasture contamination with fluke eggs, leading to a reduction in fluke larval challenge in late summer and autumn 2016.

Not all sheep with chronic infections develop classic “bottle-jaw” so fluke can potentially go unnoticed. Poor scanning results are often the first sign of an infection and can be limited to specific groups of animals, depending on their exposure to infective fluke at autumn and winter grazing.

Sioned Timothy, veterinary adviser for Merial Animal Health said: “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.”

Treatment is advised in sheep that are likely to have been exposed in the autumn and early winter, or where diagnostic tests have identified the presence of fluke in the flock.

Ms Timothy continued: “Flukicides such as those containing nitroxynil (Trodax®) or closantel are effective at treating fluke from seven weeks post-infection.

"Selecting an appropriate product based on the stage of fluke being treated, and observing good practice when treating sheep to ensure accurate dosing will maximise the efficacy of treatments, whilst minimising the risk of selecting for resistance.”

Weighing a number of different sheep will enable a representative bodyweight range within the flock to be identified, and will help avoid under or over-dosing. Whilst underdosing will compromise the efficacy of treatments, overdose carries a risk of toxicity. Groups should be treated separately where there is a significant difference in weight between different groups of animals.

Sheep should be moved to clean pasture after treatment, where supplementary feeding may be required to maintain or improve condition in affected animals.

The risk of sheep scab may continue into April. If left untreated, scab can cause weight loss due to disturbed grazing patterns and the consequent reduction in feed intake. Sheep may be seen kicking at their chest and rubbing against fences.

The fleece of affected animals will often be wet, sticky and yellow, and may be contaminated with dirt from the hind feet. Fleece loss is common where infections have been present for eight weeks or more, with bare patches sometimes extending up to 20cm in diameter, surrounded by an area of inflammation and sticky exudates.

In cattle, heavy adult liver fluke burdens may now be identified by rapid weight loss and diarrhoea, which can increase finishing times by several weeks and impact significantly on cost of production.

Over a fifth of British cattle livers are condemned at the slaughterhouse due to liver fluke damage. Asking the abattoir for feedback on liver condemnation can help identify if there is a fluke issue within the herd.

“Out-wintered 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,” said Ms Timothy.

Adult fluke in beef cattle can be treated with a straight flukicide product such as those containing nitroxynil or closantel, or a combination product where treatment of worms is also required.

TheCattleSite News Desk

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