Liver fluke is caused by infection with Fasciola hepatica which is a parasite that infects the liver in both cattle and sheep. For part of its life cycle, it inhabits the mud snail, Galba truncatula. This important stage of the parasite life cycle necessitates wet and warm conditions (above 7 - 10°C) typically seen from late spring to early autumn. It is worth noting that if there are no mud snails present on grazing land, the life cycle cannot be completed.

Eggs from infected animals will hatch, weather dependent and form intermediate stages that migrate from faecal pats, finding a mud snail to inhabit. Within the snail they undergo two further developmental stages, including multiplication, eventually becoming infective cercariae, which emerge from the snail when the temperature and moisture levels are suitable.

Following ingestion from the pasture, the young flukes migrate to the liver, through which they tunnel, causing considerable tissue damage. Adult fluke are present within the bile ducts about 10-12 weeks after the immature fluke are ingested. The whole cycle takes 18-20 weeks.

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Liver fluke causes three types of disease: acute, sub-acute and chronic. Which form occurs depends on the numbers of infective young fluke ingested and the period of time over which they are ingested.

Sheep affected by acute fasciolosis die suddenly from haemorrhage and liver damage with the first evidence of a problem being sudden deaths in previously healthy sheep from approximately August to October. The rest of the group may be lethargic and grazing less. Gathering may prove difficult because sheep are reluctant to run due to abdominal pain. Financial losses can be significant with up to 10% of at-risk sheep affected by sudden death.

Major findings with subacute fluke are rapid loss of body condition and poor fleece quality despite adequate flock nutrition. Typically, some sheep present with severe depression, inappetence, weakness and may be unable to stand. Losses typically occur from December onwards but may be much earlier (October) with severe challenge.

York Press: The first sign of actual fluke in sheep may be sudden deathThe first sign of actual fluke in sheep may be sudden death

Chronic fasciolosis results in very poor body condition score, poor fleece quality and bottle jaw. Affected sheep may die in an emaciated state especially when infestation is compounded by the metabolic demands of advanced pregnancy/early lactation.

Cattle typically develop chronic disease and classically show loss of weight and condition and may become anaemic.

Treatment of fluke infections requires selection of an appropriate product that will act against the life stage present within the animal. For more information or to discuss a Fluke Control Plan for your herd or flock please ring the practice and speak to one of the team.

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Derwent Vale Farm Vets

Unit 3, Thornton Road Industrail Estate

Pickering

North Yorkshire

YO18 7JB

Tel: 01751 469343