As forecast earlier in the year, this season's forecast indicates that there is a risk of very high levels of liver fluke disease in all of Scotland, Wales and western England. Although figures are not available to produce a Northern Ireland forecast, climate data also suggest a very high risk there. Fluke disease is forecast to be a significant risk across most of the rest of the UK, although the figures for East Anglia are at a level usually associated with a low risk of disease. Localised areas that have remained wet for long periods over the summer and autumn may present a threat to livestock in any part of the country, and the fencing-off of such areas provides some control of infection without increasing selection for flukicide resistance.

The first sign of a fluke problem on a farm might be seen in January when poor scanning results are obtained. At this time of year, there is often a mixture of adult and immature fluke in the liver causing condition loss, dullness, anaemia, abdominal pain and sometimes death. This is termed sub-acute fascioliasis.

Deaths due to acute and sub-acute disease may continue in many regions into the winter. Mean daily maximum temperatures for November were just 10 °C in southern England, and lower across the rest of the UK, indicating that little fresh fluke infection will have been passing from snails onto the pasture.

However, the infectious stages (metacercariae) already on the pasture are highly resilient, so cases of acute fluke may therefore occur through January or even later, particularly in the high-risk regions. If there is severe penetrating frost, this will reduce their numbers and therefore reduce the risk of fresh infection of livestock.

Farms with a history of fluke should consider a winter (December/January) dose to remove adult and immature fluke. Sheep in high-risk areas may remain exposed to potentially risky pastures through the winter and consideration should be given to administering a repeat dose to these animals 4-6 weeks later.

source: National Animal Disease Information Service.