Cumbria and Yorkshire farmers have joined forces to fight the challenge of living with and managing liver fluke in hill sheep flocks.
The Farmer Scientist Network has secured European Innovation Partnership (EIP-AGRI) funding and set up Hill Sheep North working with farmers and industry experts to study flock health issues and formulate strategies. The project is being facilitated by The Farmer Network.
Liver fluke is a major parasite problem in the north of England and control is difficult, particularly where flocks are only gathered for treatments several times a year, and the conditions on moors and upland fields can be ideal habitats for the mud snail host.
The days of just drenching animals to control fluke are gone. The build-up of resistance to triclabendazole is considered to be widespread, and while the total picture is unknown, pockets of resistance have been found all over the west of the UK. Wetter, warmer conditions, particularly in the west, mean that the cysts are available to be eaten nearly all the year round.
So testing for presence of fluke, grazing management and careful use of the right flukicide product to treat the right life-stage of the fluke at the right time are all key to living with fluke.
In the liver fluke project, farmers, vets and experts are sharing their knowledge and information to help form a solution, working together to improve and evaluate disease control programmes for hill flocks.
To gain greater understanding of the parasite, farmers are participating in regular testing and working closely with their vets. They have discussed their current flock treatments and are recording and linking their data with a phone app.
A questionnaire for 25 hill farms with flocks in Cumbria averaging 1,055 sheep and Dales farms averaging 592 head of principally Swaledale, Swaledale crosses, Herdwicks and Mules, highlighted fluke as the most frequently reported problem in 2018 with 16 of the farms reporting cases and mortality.
Dr Bryony Jones, Research Associate with the Royal Veterinary College and joint academic lead of the project, said among the farms that reported cases of fluke, the estimated mortality rate in the affected groups was up to 18.9%, and averaged 4.7. The proportion of the group affected was estimated to be between 1.3 to 100%, an average of 25.0%. These estimates were similar in Cumbria and Dales farms.
“Most fluke cases were diagnosed by the farmer, but some were vet-diagnosed by post mortem and/or lab tests, and some were based on abattoir feedback.
“The reported clinical signs of fluke disease included acute cases with sudden death, and chronic cases of wasting.”
Recent workshops have been held on farm in Cumbria (Goosewell, Keswick) and Yorkshire (Cogden Hall, Grinton, Richmond).
Sheep flock health specialist Fiona Lovatt explained to the Richmond meeting how it is important to use the most appropriate medicine for the time of year and life stage of the fluke.
She advised identifying which fields and which groups of livestock are most risky. Graze any finishing lambs in fields where there are no snails so that you won’t have to treat them with flukicide.
She said: “The products that only treat adults – e.g.albendazole, (short withdrawal period for meat), will not treat any immature fluke which are damaging the liver of these lambs, so it is pointless using this flukicide in the autumn.
“If they are picking up cysts and carrying immature fluke, they need to be treated with closantel, nitroxynil or triclabendazole and of course they won’t be able to be slaughtered until after the withdrawal period. Hence ideally weaned lambs need to be somewhere where they are not picking up the cysts so they don’t need treatment.
“It is also very important to protect any snails on your farm from being infected by fluke from other farms, particularly those at high risk of being resistant to triclabendazole.
“This can be done by keeping any bought in sheep in a dry field, which doesn’t have any snails. Dose the new sheep twice with a closantel or nitroxinil product, six or seven weeks apart, to make sure that any fluke that is resistant to triclabendazole is killed before the new sheep go into an area where they could infect any snails living on your land.”
The best way to avoid over-treating, under-treating or treating with the wrong product is to check what is present in flock, especially testing at the right interval after treatment to see if the product has worked.
A range of tests are available. Monthly faecal egg counting provides a guide to when numbers of adult fluke are increasing in the sheep. This can be done on the farm, following instructions provided in the Moredun Foundation handout, or through the farm’s vet practice.
At the Keswick meeting, alongside Dr Phillip Skuce, of Moredun Research Institute was joined by national liver fluke researcher Dr Rhys Jones, of Aberystwyth University, who studied one farm for fluke alongside livestock management for five years, explained the activity of mud snails and fluke.
“Mud snails are most active from April to October, some overwinter and then die in the spring and some die in dry conditions over the summer. But we mainly see the symptoms of fluke in livestock mainly in the autumn/ early winter.
“Moisture in summer is the most important factor for the snail – they can survive in moist conditions for months, but can survive in dry conditions for only one month.
“Thick grass, or moss without any bare mud is not good habitat for snails. Light poaching by livestock disturbs the surface and allows bare mud to be colonised by algae – which the snails graze.”
He explained that the underlying geology affected how dry, wet or acid the conditions are for snails. They did not colonise soil that is sandy, peaty, or less than pH 5.1 – or deep water, but slow-moving streams.
In dry years livestock tend to graze the wetter areas that they wouldn’t go into in wet years – sometimes these are more risky areas.
“We had a problem in the autumn of 2017 after a particularly wet summer with a lot of the ewes returning to service and not thriving,” said Carol. “The protein levels in the blood were indicative of fluke. I am a member of local group Ladies in Livestock and our vet Sarah Harker had shown us how to do a liver test post mortem and I found it to be infested with adult fluke.
“Since we have joined the project we have tried to avoid using triclabendazole and used flukicides more often. We have a much better understanding of the liver fluke cycle and we can make decisions on whether to dose the sheep. We are using the special app where we can record treatment details.”
Carol and her father are also making some adjustments to grazing management including running sheep in smaller groups to help avoid poaching. The farm’s meadow ground can be boggy and this is grazed by lambs before they are sold in September – the gimmers are sold for breeding and weathers store.
The weathers are also sold sooner in advance of the ewes being flushed on the meadow ground.
“As well as learning more about fluke and its treatment, the project has allowed us to share and discuss our problems with other sheep producers,” said Carol.