Squirrels, like many other small animals, can transmit pathogens. Now researchers have discovered that people in the Middle Ages could have contracted leprosy from squirrels.

Leprosy is a bacterial disease that attacks the skin, nerves and mucous membranes. It is one of the oldest diseases known to mankind. It was widespread in Europe in the Middle Ages, but today the disease is almost non-existent on the continent. Around 95 percent of new cases occur in the countries of the Global South. More than 200,000 new cases are registered every year. Leprosy can be treated today. If this is not the case, it can lead to serious disabilities.

So far, cases of leprosy have been found in armadillos and it is suspected that they transmit the disease to humans. There are also cases of leprosy in red squirrels in Great Britain. So far there has not been a single case of transmission to humans.

Now, for the first time in England, a medieval animal has been identified as the host of the disease. "It was surprising that leprosy could be found in modern squirrels. The fact that we could now find the disease in squirrels from the Middle Ages is incredible," says Dr. Sarah Inskip from the University of Leicester told the BBC. The co-author of the new study says this finding completely contradicts the narrative that leprosy is an exclusively human disease.

It remains unclear whether squirrels would have infected people in the Middle Ages or exactly the other way around. Squirrel fur was often used for fine clothing in the Middle Ages, and some even kept the rodents as pets.

The research group analyzed 25 human and 12 squirrel samples that came from a Winchester leprosy hospital and a pit used by fur traders in the immediate area. The English city was known in the Middle Ages for its large leprosy and its connections to the fur trade. One could have caused the other, shows the study by Prof. Verena Schünemann and her team from the University of Basel. The study found that one of the ancient leprosy bacteria strains from a squirrel was closely related to the strains of humans at the time.

However, exactly how the disease spreads from person to person is still not known. Anyone who has close contact with infected people for a long time runs the risk of becoming infected. But it is relatively difficult to transmit to healthy people via droplets. "The history of leprosy is much more complex than actually assumed," Prof. Verena Schünemann told the BBC. More research is still needed to find out more about the transmission of this serious disease.

Sources:   RKI, BBC,  Spectrum of Science.