Janssen Animal Health is warning sheep farmers to be on the look out for sudden deaths in their flocks this autumn as acute fascioliasis due to liver fluke is predicted to reach high levels. The chronic form of the disease can also cause barren ewes and reduced lambing percentages and as tupping time approaches those in previously unaffected areas need to be reviewing the threat posed by fluke to avoid poor results in the spring.
Both acute and chronic fascioliasis can be prevented by implementing a strategic control programme using effective flukicides on a rotational basis. This approach can both minimize the risk of resistance developing to flukicides, which is an important consideration given reports of triclabendazole resistance across the country, and can be effective in reducing pasture contamination and subsequent fluke infections.
NADIS has already suggested that this year there is a very high risk of fluke in Scotland, North West England and Wales, a high risk in North East England, South Wales, South West England and the Midlands and occasional outbreaks predicted over the rest of the country attributed to the ideal weather conditions allowing fluke to proliferate.
The Met Office has reported that summer rainfall across the UK was 40 per cent up on the long-term average and temperatures up by 0.6 degrees centigrade. Janssen Vet Nigel Underwood explains the risks, “The warm wet summer this year and for several years preceding this winter, has resulted in ideal conditions for fluke development – these conditions favour the lifecycle of the mud snail – an important intermediate host for fluke as well as benefiting the development of the infective fluke stages. The warmer autumn is also likely to extend the fluke challenge period as the increased mud snail population survives for longer and also infective stages of the fluke will be ongoing. Closantel will kill fluke and also causes marked stunting of earlier immature fluke i.e they never develop fully. These fluke lay fewer eggs and the eggs they do lay have reduced viability. Closantel disrupts egg laying and the viability of eggs for 13 weeks – longer than any other flukicide.
This autumn and winter the priority should be to prevent deaths from acute fluke outbreaks and then to reduce the burden of fluke within over-wintered animals. For the last few years liver fluke has also become an increasing risk in traditionally drier areas to the east where cases of sudden death due to acute disease may initially be attributed to other causes. Up to 10 per cent of the flock can be lost due to a large autumn fluke challenge – the migrating immatures causing liver haemorrhage and severe damage. Surviving sheep can also show lethargy and reduced grazing activity which can impact productivity.
Fluke is a cause of major economic loss to the sheep farmer – autumn deaths are apparent but the following spring there can be a dire consequential results at lambing time. This is a particular risk in areas where fluke has not been endemic and therefore preventative treatment has not been adopted as part of the farmers’ parasite control protocol. Janssen say that farmers should be talking to their vets and animal health advisers to assess the potential risk in their area and be alert to the signs of the disease. They should also discuss ways to develop a more strategic approach to fluke control – minimizing the level of disease on the farm as well as minimizing the risk of resistance to flukicides. The recommended frequency and timing of treatment will vary according to climatic conditions and the individual farm.
Further information is available from Janssen Animal Health, 50-100 Holmers Farm Way, High Wycombe, Bucks, HP12 4EG Tel 01494 567555 Fax 01494 567556 Email: ahealth@jacgb.jnj.com
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