May 25, 2024

Leprosy was transmitted between humans and red squirrels in medieval England, research suggests, supporting the theory that the fur trade may have played a role in the spread of the disease.

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

While most cases now occur in Southeast Asia and can be treated with antibiotics, leprosy was common in medieval England and caused disease and disfigurement in rich and poor alike.

Previous research revealed that people in medieval England, Denmark and Sweden had a similar type of leprosy to that found today in red squirrels in the south of England, with one theory being that the trade in squirrel furs, imported from Viking Scandinavia, may have been a factor in the spread of the disease.

Now experts say the theory has received a boost, with genetic analysis revealing that red squirrels in medieval England experienced a very similar strain of the disease to humans living at the time.

“This is the first time we’ve found a leprosy host in the archaeological record, which is really exciting,” says Dr Sarah Inskip from the University of Leicesterwho co-authored the research.

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

Write in the journal Current BiologyInskip and an international team of colleagues report how they studied strains 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 pit in the city is dating from 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 a host of hide processors involved in the preparation and sale of fur-lined clothing – meaning it was possible to find squirrels and to obtain human remains from the time.

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

“In fact, the strains that are in the archaeological squirrels and the archaeological people of Winchester are more closely related than the strain that is in the medieval squirrels [and] the tribe that is in modern squirrels,” Inskip said.

The team says the results indicate that 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 people initially contracted leprosy from red squirrels or vice versa.

Inskip said that even in the latter case the animals can transmit the disease to humans, noting that while humans first gave the disease to armadillos in the Americas, they can now catch it from the animals.

“We know that it can ping pong backwards and forwards,” she said.

Inskip added that there are a number of possibilities for how transmission may have occurred.

“One mechanism would be the fur trade,” she said. Indeed, the study states that in 1384 alone, 377,200 squirrel skins were imported into England from Scandinavia and elsewhere.

However, squirrels were also widely kept as pets, providing another route of contact with humans.

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

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

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

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