Squirrels may have given medieval Britons leprosy

Humans may have caught leprosy from squirrels in medieval times, researchers say.

They studied human and red squirrel bones from archaeological sites in Winchester, southern England, and found they had closely related strains of the bacteria that causes it.

Leprosy is a chronic disease infectious between humans that attacks the skin, nerves and mucous membranes.

Armadillos carry it and are suspected of passing it on to humans. Some modern red squirrels in the UK also have it, but there have been no reported cases of transmission to humans.

It’s the first time a medieval animal has been identified as a host for the disease.

"The finding of leprosy in modern squirrels was surprising and then it's incredible that we found it in the medieval period," said study co-author Dr Sarah Inskip of the University of Leicester.

"It really goes against the narrative that it was a human disease specifically," she said.

It's not clear whether squirrels in medieval times gave humans leprosy or the other way around.

But the shared strain suggests it was circulating between people and animals in the Middle Ages in a way that hadn’t been detected before, the researchers say.

Back then, squirrel fur was used as a fine lining for clothes and some people also had pet squirrels. They were particularly popular with women.

A depiction of a medieval woman playing with a red squirrel wearing a belled collar
A woman plays with a pet squirrel wearing a belled collar in the Luttrell Psalter, a book created in Lincolnshire, England, in the early 14th century [British Library Board]

The researchers studied 25 human and 12 squirrel samples.

The human remains came from a Winchester leprosarium (hospital for people with leprosy) and the squirrel remains from a nearby pit used by furriers.

Previous studies found that modern red squirrels from Scotland and Brownsea Island off the coast of southern England carry leprosy.

Public health England says the probability of humans catching it from squirrels is very low and there has never been a reported transmission.

Leprosy is one of the oldest recorded diseases in human history and is still present in Asia, Africa, and South America.

There are more than 200,000 new cases reported every year.

It's not known exactly how it spreads between people but prolonged, close contact with someone untreated, over many months, is needed to catch the disease.

“The history of leprosy is far more complex than previously thought,” said senior author of the study, Prof Verena Schünemann of the University of Basel in Switzerland.

“There has been no consideration of the role that animals might have played in the transmission and spread of the disease in the past, and as such, our understanding of leprosy’s history is incomplete until these hosts are considered."

Dr Stephen Walker, Associate Professor at London School of Hygiene and Tropical Medicine said: "There's no doubt that in certain circumstances animals do appear to play a role, but the size of that role in global terms of leprosy hasn't been delineated and I would agree, does need more work.

"I think it highlights that we still have a lot of work to do to understand the transmission of this ancient disease better, in our efforts to try and reduce the impact globally."

The study is published in the journal, Current Biology.