Leprosy is endemic among red squirrels in the UK

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Researchers in continental Europe and the British Isles have recently made a shocking discovery: Leprosy seems to be endemic among the red squirrel populations of the British Isles.

Leprosy affects the skin, lungs, eyes, and parts of the nervous system. It is one of the oldest recorded and still occurring diseases known to humanity, and it has had serious social impacts on cultures around the world and throughout history.

Though it is little discussed these days, about 200,000 new cases are reported each year, though antibiotics generally keep it under control. It is also little known that the disease can and does infect some animal species too, most notably armadillos, but also, it appears, red squirrels.

“It was completely unexpected to see that centuries after its elimination from humans in the UK, [leprosy bacteria were causing] disease in red squirrels,” says Stewart Cole, one of the researchers. “This has never been observed before.”

While the researchers don’t believe there is cause for alarm, partly because humans have little actual contact with red squirrels, but also because transferring a disease from an animal to a human, known as zoonotic infection, is pretty uncommon. The World Health Organization does monitor leprosy, so outbreaks would likely be caught in time to prevent an epidemic.

But leprosy in red squirrels does pose some concerns from a conservation point of view, as the disease, whether it is actively affecting individual squirrels or not, seems to be very common among them. The researchers did DNA tests on 110 specimens and found that almost all were infected, although not all showed clinical signs of the disease. The strain found among red squirrels on Brownsea Island in the UK was the same as that found in a 730-year-old skeleton from Winchester.

For now, researchers are looking into how leprosy spread to red squirrels and went unnoticed for so long. Once they have a better grasp on that, they can begin to look at ways to prevent its spread and keep it from potentially wiping out the entire species, or spreading to other animals.