Senior vets have warned an outbreak of a potentially deadly livestock disease is likely to recur next year.

A new strain of the bluetongue virus, which is spread by midges, has affected large parts of the east of England in recent months.

There have also been two isolated cases in north Wales, caused by the movement of animals before restrictions came into force.

Dr Sioned Timothy, who heads pharmaceutical giant Boehringer Ingelheim’s livestock vet team in the UK, said the potential impact was massive in Wales if it took hold.

While midge activity is set to reduce over the winter months, farmers are being urged to remain vigilant for signs of the infection, which does not affect people or food safety.

“We may be fortunate that the weather goes in our favour and for this season the further spread of the virus is curtailed,” explained Dr Timothy.

Her company is behind one of three newly-developed vaccines which have not yet gone through the full authorisation process but have been granted emergency approval for use in England.

“We know from the experience in the Netherlands, where the outbreak has been more extensive and the clinical signs have been worse this year than in previous years that it is likely to recur,” she said.

“We do need to look forward and have a plan in place for what to do should the risk persist,” she added. “The key thing is for farmers to be vigilant”.

The latest outbreak began in the Netherlands in 2023 and has spread widely across Europe this year, with midges blown over from the continent infecting sheep and cattle in the UK.

A restriction zone, limiting the movement of animals, is now in place across 20 counties in England – ranging from the south coast to parts of North Yorkshire.

Last week it was announced that the English Winter Fair – a major agricultural show – due to be held in Staffordshire in mid-November had been cancelled.

Dr Timothy, who lives in Newcastle Emlyn, Carmarthenshire, said the “relatively low livestock population” in the east of England “will have limited the spread in some ways”.

Should the disease spread in Wales – where sheep and cattle farms dominate the agricultural landscape – “the potential impact is massive”, she said.

Bluetongue virus affects wild and domestic animals, such as sheep, goats, cattle and deer.

It can cause ulcers or sores around the mouth and face, difficulties swallowing and breathing, fever and lameness.

It does not affect humans and the Welsh government has said there is no risk to public health or food safety.

Sheep are more affected by the latest strain – known as BTV-3 – though the disease’s impact seems to vary considerably across different regions, with some animals showing little sign of infection.

In the Netherlands, tens of thousands of sheep have died.

“We’re still dealing with an unknown potentially,” Dr Timothy warned.

A total of 12 cases of BTV-3 have been detected so far outside the current restricted zones – all of which were animals moved from areas where the disease is now known to be circulating before restrictions were in place.

They include two cases in north Wales in recent weeks – involving three sheep on a farm in Gwynedd and an unidentified animal on Anglesey – all of which were culled.

Gwynedd Watkin, of the Farmers’ Union of Wales in Gwynedd, said the local community had been very concerned by the news.

“What gave us peace of mind was that the sheep suffering from bluetongue had recovered from it, and also that the system of licensing the movements of animals (had meant) they were able to trace where the disease had come from.”

“We encourage our members to be vigilant and to be especially careful from where they purchase their livestock,” he added.

Wales’ chief veterinary officer Dr Richard Irvine said investigations had been carried out at both locations to ascertain whether the virus had entered the midge population.

This work had concluded for the first farm in Gwynedd with no evidence of local bluetongue infection.

“We’re working through surveillance for the second farm and we hope that will yield a similar outcome,” he said.

The disease was “very much” on the Welsh government’s radar, he added, with officials “thinking very carefully about the next few weeks, months and into the spring”.

“Hopefully we will not see that increased severity of cases that were reported in northern Europe,” he said.

“But certainly we need to be prepared – as well as taking those immediate actions here in Wales to be vigilant, report cases, source stock responsibly and protect the national herd and flock from bluetongue”.

A stakeholder group involving farming and veterinary organisations had been meeting for a number of months to assess the situation, he said.

The potential role of new vaccines was part of this discussion, but currently they were “new to market products” that are “not fully protective,” he added.

Both Dr Irvine and Dr Timothy warned that climate change may mean the disease becomes more of a familiar problem in the UK.

“Historically the textbooks would tell us that bluetongue going back several decades was a disease predominately seen around the Mediterranean basin,” Dr Irvine said.

“We’re certainly seeing a shift in the pattern of a lot of diseases as temperatures warm up and seasons become less defined,” Dr Timothy added.

“It’s likely that the type of midges – for instance – that are required for transmission of some of these vector-borne diseases will become more prevalent.”

Bluetongue is a notifiable disease so anyone suspecting the disease must report it to the Animal and Plant Health Agency (APHA).