30th March 2018

New Video Highlights Control Options for Liver Fluke in Sheep

Establishing whether your farm has a liver fluke problem,  managing your grazing tactically and using the right product at the right time are three of the key messages in a new video launched this week to help farmers control liver fluke in their sheep.

In the video, launched by Quality Meat Scotland (QMS), sheep vet Fiona Lovatt gives an overview of the problems liver fluke can cause in sheep, and highlights practical steps farmers can take to minimise production losses from the parasite.

“The control measure that is most appropriate at this time of year is to avoid turning out sheep that are shedding fluke eggs – as these will infect your snails and hence lead to further contaminated pastures by the end of the summer,” said Dr Lovatt, who runs a sheep veterinary consultancy business, Flock Health Ltd.

Dr Lovatt was one of the main speakers at a series of worm and fluke control meetings for farmers arranged by QMS last month. At the meetings she explained that, at this time of year adult fluke living inside infected sheep will be laying eggs that can be identified in the sheep’s faeces. 

She added: “Many farmers do not realise they have a chronic liver fluke problem until they have poor scanning results or they are faced with thin ewes. Don’t try and guess what the issue is – take muck samples from thin ewes at scanning time or before turnout and check if fluke are present.”

The liver fluke parasite has a complex life cycle that uses both grazing livestock and mud snails as hosts.  Adult fluke live in the bile ducts of sheep (or cows) and lay  eggs, which pass out in the faeces and hatch into larvae on the pasture. The larvae burrow into mud snails where they multiply.  After one to three months, depending on environmental conditions, fluke leave the snail and encyst on grass for sheep or cattle to eat. Once inside livestock, the young fluke travel to the liver.  Over the next 12 weeks they will develop to adults and again start laying eggs. 

If large quantities of immature fluke, are accidentally eaten by the sheep, cause acute disease and death from blood loss and liver damage.  In fact, sudden death, in the autumn or winter, can be the first evidence of there being a fluke problem.

Signs of a chronic fluke burden in sheep are seen later in the winter or into the spring, once adult fluke have developed.  Sheep with chronic fluke may be in poor body condition, have reduced fertility and a poor milk supply which will then lead to increased mortality and reduced growth rates in their lambs.

Feedback from the abattoir or from fallen stock can also give farmers an indication if they have fluke on their farm. Otherwise, in late summer or early autumn, when the risk of acute fluke is high, lambs in their first grazing season can be blood tested to detect the first sign of fluke, and alert farmers that they need to treat with a flukicide that kills immature fluke.

There are three groups of flukicide that kill liver fluke.  Many will only kill adult fluke – these are appropriate to use in the spring but not in the autumn when the fluke in the sheep are immature.  Some products will kill the older immatures as well as the adults.  But only Triclabendazole will kill fluke at all stages of its life cycle – so this is the most appropriate product in the autumn when immature fluke are active and stock are at risk of acute fluke disease.

“Because of the risk of resistance to drugs, it is important to monitor fluke levels and to manage your grazing appropriately so you are not relying on drugs unless completely necessary,” Said Dr Lovatt.

Because fluke need the snails which live on mud, Dr Lovatt advised farmers to, wherever possible, keep vulnerable stock off snail-inhabited pastures at high risk times of year, such as the autumn.

As each farm and year brings different fluke risks, Dr Lovatt highlighted that it was important for farmers to draw up a fluke control plan in conjunction with their vet or sheep advisor. With limited products available to treat, making sure that the right product is used at the right time, and that it is effective is essential to ensure good control on each farm.

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