CUMBRIANS are being urged to stay vigilant to help protect the county's treasured red squirrel population.

The call from conservation volunteers comes after a potential case of the fatal squirrel pox virus was spotted at a nature reserve by an amateur wildlife photographer.

The infectious disease, carried and spread by grey squirrels, results in death for most reds within 15 days.

Although the "possible" case spotted at Smardale Nature Reserve near Kirkby Stephen has not been confirmed, it has led to renewed calls for vigilance among the public to help conserve one of the Lake District's most iconic creatures - immortalised in Beatrix Potter's Tale of Squirrel Nutkin.

Cumbria, and Northumberland, are two of the last places in England where reds still exist.

People are being encouraged to report sightings of healthy or sick red squirrels, as well as any greys, to local volunteer groups so they can continue to keep a close eye on numbers and carrying out trapping or culling where required.

Cumbria Wildlife Trust has also taken to social media to encourage residents living locally to its 49-hectare Smardale site to disinfect any squirrel feeders using Virkon S, widely available online and through agricultural suppliers.

Greys are immune to squirrel pox, whose symptoms include lesions around the eyes, ears, nose and paws.

Sunday's possible sighting was made by Cumbria Wildlife Trust volunteer Matt Staniek, 23, a zoology graduate from Windermere.

"It's a real red alert because it can wipe through a population and completely destroy them," said Mr Staniek, who is pursuing a career as a wildlife presenter.

Bob Cartwright, deputy chairman of volunteer group Westmorland Red Squirrels, said news of the potential case "makes your heart sink".

"It's compounded because so many volunteers like ours and other groups are working so hard to get the reds back and protect the populations," he told the Gazette. "If you do get an outbreak it's heartbreaking."

Mr Cartwright said there had been "something like 11,000" reported sightings of red squirrels in Cumbria this year, compared to more than 9,000 greys culled in the county. He said thanks to "boots on the ground" by the county's 14 volunteer groups - under the umbrella body of Northern Red Squirrels - red numbers in Cumbria were "relatively stable".

Efforts are being made to reduce grey squirrels in woodlands around the Arnside and Silverdale peninsula to create a "buffer zone" to prevent squirrel pox spreading northwards.

Volunteers across Cumbria were "not prepared" to see red squirrel populations die out, said Mr Cartwright.

"You couldn't imagine the Lake District without Herdwick sheep or the lakes. It's the same with red squirrels. It would be awful if on our watch we saw them disappear. What kind of heritage would we be passing on if we lose our red squirrels?"

Simon O'Hare, project manager for the Red Squirrels Northern England project, which takes an overview of all volunteers' efforts, said it was impossible to put a number on Cumbria's population of reds. But a survey this year found the creatures at 64 per cent of sites visited. "This really does show Cumbria is the place for red squirrels," he said. "The context of that is it takes a lot of people's time and effort to keep it like that. We are talking hundreds of volunteers."

Bonnie Sapsford, the project's red squirrel officer, said it was "almost impossible to confirm pox cases just by looking, due to similarities in symptoms to other afflictions such as extreme cases of dermatitis around the eyes and face".

She said, for confirmation, carcasses should be sent off for testing to the Animal and Plant Health Agency, and that other typical symptoms such as lesions round the mouth and feet could not be seen in Mr Staniek's photograph.

Mr O'Hare said the pox virus did "pop up every now and again" in Cumbria, and the message was that local vigilance was "really important", with people encouraged to report any sick reds squirrels to their local volunteer group immediately - see www.northernredsquirrels.org.uk/nrs-groups/cumbria-groups/ for details.

Since Sunday's possible pox sighting, volunteers have been out looking for other potential cases at Smardale, said Mr O'Hare, but fortunately so far have only seen "lots of healthy reds".

He described the red squirrel as "a flagship species"with "iconic status" for the county. "It's really important for us to ensure we continue to conserve them and don't let them disappear within our time," he said.

"We are extremely lucky to have this animal still: this really charming and engaging animal in our woodlands across Cumbria. That's because of the time and effort of hundreds of local people on the ground. There's no doubt about it, without the volunteers we simply wouldn't still have red squirrels across Cumbria."

National Trust property Allan Bank, William Wordsworth's former home at Grasmere, is renowned as one of the most likely places to spot a red in Cumbria. Dave Almond, the trust's countryside manager for central and eastern Lakes, said outbreaks had happened in the past, often around this time of year.

"The very sad thing is once red squirrels become infected they become a vector, passing it on to other reds, so they must be taken out of equation," he said. Mr Almond said Grasmere's population was currently "nice and healthy", and the National Trust worked closely with the volunteers of Grasmere Red Squirrel Group to protect it. He also backed the call for continued vigilance from the public.

Anybody wishing to fund red squirrel conservation work can do so via National Trust properties, local groups via the Northern Red Squirrels website, or by joining the Friends of Red Squirrels at www.rsne.org.uk