Leprosy occurred between medieval squirrels and humans, research suggests

Leprosy occurred between humans and red squirrels in medieval England, research shows. This supports the theory that the fur trade could have played a role in the spread of the disease.

Leprosy is one of the oldest recorded infectious diseases in humans and is usually caused by the bacteria Mycobacterium leprae.

Although most cases now occur in Southeast Asia and can be treated with antibiotics, leprosy was common in medieval England, causing illness and disfigurement in both rich and poor people.

Previous research showed that people in medieval England, Denmark and Sweden had a similar form of leprosy found today in red squirrels in southern England, theorizing that the trade in squirrel fur, imported from Viking Scandinavia, might have been a factor in the spread of the disease.

Now experts say the theory has gained momentum, with genetic analysis showing that red squirrels in medieval England experienced a very similar form of the disease to people living at the time.

“This is the first time we have found an animal host of leprosy in the archaeological record, which is really exciting,” said Dr Sarah Inskip from the University of Leicester, who co-authored the study.

A squirrel bone found at one of two archaeological sites in Winchester. Photo: Alette Blom/University of Basel/PA

Writing in the diary Current biologyInskip and an international team of colleagues report how they studied forms of leprosy found in samples from three people who lived in Winchester between 900 and 600 years ago, and a squirrel whose bones were found in a fur quarry in the city dating back to between 1,000 and 900 years ago.

The team focused on Winchester because it was an important city in the Middle Ages and had a leper hospital and numerous skinners involved in the preparation and sale of fur-lined clothing – which meant it was possible to recover squirrel and human remains from those to get time.

The team extracted and analyzed DNA from the samples, which showed that a very similar form of leprosy was present in all samples.

“In fact, the tribes of the archaeological squirrels and the archaeological people of Winchester are more closely related than the tribe of the medieval squirrels (and) the tribe of the modern squirrels,” says Inskip.

The team says the results suggest the disease was transmitted between humans and squirrels.

A computer illustration of Mycobacterium leprae bacteria. Photo: Kateryna Kon/Getty Images/Science Photo Library RF

However, the findings are based on just a handful of samples, and the results cannot shed light on whether humans initially contracted leprosy from red squirrels or vice versa.

Inskip said that even in the latter case, the animals could transmit the disease to humans, noting that while people first gave the disease to armadillos in America, they can now get the disease from the animals.

“We know it can ping-pong back and forth,” she said.

Inskip added that there were a number of possibilities as to how the transfer occurred.

“One mechanism would be the fur trade,” she said. In fact, the study reports that 377,200 squirrel skins were imported to England from Scandinavia and other places in 1384 alone.

However, squirrels were also widely kept as pets, providing another means of contact with people.

“Both mechanisms are possible. And they are not mutually exclusive either,” says Inskip.

Inskip said the study also had implications for people suffering from leprosy today.

“Maybe we should start looking at the animals that live around these communities,” she said. “Because maybe it’s possible that some of these animals have the bacteria and that might be why the disease is hanging around.”