Red squirrels in the UK carry leprosy, scientists discover

Chances of catching disease are extremely low and those living close to the animals should not worry, researchers say

Brownsea island in Dorset is home to over 250 red squirrels (John Millar/National Trust Images)

Red squirrels in the UK carry strains of leprosy similar to those that have afflicted disability and disfigurement on humans for centuries, a study has shown.

Experts stress the chances of catching the disease from a squirrel are extremely low and have urged people living close to the animals not to panic.

Scientists tested DNA samples from 25 red squirrels living on Brownsea Island, Dorset, and found that every one was infected with the leprosy bacteria Mycobacterium leprae.

The strain was strikingly similar to that recovered from the skeleton of a leprosy victim buried 730 years ago in Winchester - just 43 miles away.

Other red squirrels from Scotland, Ireland and the Isle of Wight were carrying another kind of leprosy bacteria, Mycobacterium lepromatosis. This strain was closely related to a virulent form of human leprosy endemic in Mexico and the Caribbean.

Brownsea Island in Poole harbour is a red squirrel haven containing a thriving population of about 250 of the endangered rodents.

The new study suggests the island's red squirrels have been affected by leprosy for decades and perhaps centuries.

Not all the infected squirrels were displaying symptoms. Those that did showed signs of swelling and hair loss from the ears, muzzle and feet.

In humans, leprosy causes nerve and muscle damage which left untreated can lead to deformity, disability and blindness.

The scientists have played down the risk to humans, pointing out that the vast majority of healthy people are naturally immune to leprosy and will not be affected even if exposed to the bacteria.

Despite popular myths about leprosy leaping from person to person through physical contact, the infection is not highly contagious. It is believed to be spread chiefly by coughing or sneezing.

Professor Anna Meredith, from the University of Edinburgh's Royal School of Veterinary Studies, who led the Anglo-Swiss team, said: "The discovery of leprosy in red squirrels is worrying from a conservation perspective but shouldn't raise concerns for people in the UK.

"We need to understand how and why the disease is acquired and transmitted among red squirrels so that we can better manage the disease in this iconic species."

Swiss colleague Dr Andrej Benjak, from the Ecole Polytechnique Federale de Lausanne (EPFL), said: "There is no reason for panic.

"The next logical step after this study is to check the red squirrel population outside the British Isles. Even if there is leprosy in red squirrels in continental Europe, the risk of transmission to people is generally low because of their limited contact with humans, and hunting red squirrels is forbidden in most European countries."

In total, the cadavers of 110 red squirrels from England, Scotland, and Ireland were tested.

Dr Stewart Cole, also from EPFL, said the discovery of the medieval M. leprae leprosy strain in the Brownsea Island squirrels so long after its elimination from humans was "completely unexpected". He added: "This has never been observed before."

The last recorded case of indigenous leprosy contracted in the UK dates from 1798.

Each year, around a dozen people are treated for the disease in the UK after being infected abroad. The infection is still prevalent in South America, Africa and Asia.

Animals - not necessarily red squirrels - may act as reservoirs for the bacteria in parts of the world affected by leprosy, the findings published in the journal Science suggest.

Brownsea Island, owned by the National Trust and Dorset Wildlife Trust, will stay open while the scientists continue their four-year investigation.

Angela Cott, National Trust general manager for the island, said: "Brownsea's wild red squirrel population has been living with leprosy for at least four decades. But by working with the University of Edinburgh and Dorset Wildlife Trust, we hope to understand how best to look after Brownsea's wild red squirrels. Brownsea Island remains a spectacular place for people to see wildlife."

Fewer than 140,000 red squirrels remain in the UK and the Red Squirrel Survival Trust predicts they could vanish from Britain within the next 10 years.

They are chiefly threatened by habitat loss and the squirrelpox virus carried by grey squirrels, whose 2.5 million population vastly outnumbers that of the reds.

Today 75% of the UK's red squirrels live in Scotland. In southern England the Isle of Wight, where grey squirrels have largely been kept out by the Solent sea channel, is their main sanctuary. Red squirrels can also be found in the Lake District, Northumberland, North Yorkshire, Cornwall and Devon.