Medieval English red squirrels contained bacteria that caused leprosy, affecting our understanding of the history of the disease and transmission between humans and animals, research suggests.

Evidence from archaeological excavations in the medieval English town of Winchester suggests that British red squirrels were once an important host for the species Mycobacterium leprae, This causes leprosy in humans, researchers report in the journal Current Biology.

Genetic analysis of medieval strains

“Thanks to our genetic analysis, we were able to identify the red squirrel as the first ancient animal carrier of leprosy,” says senior author Verena Schoenemann from the University of Basel in Switzerland. “The medieval red squirrel strain we recovered is more closely related to medieval human strains from the same city than to strains isolated from infected modern red squirrels. Overall, our results suggest independent circulation of strains M. leprae “Between humans and red squirrels in the medieval period”.

“Our findings highlight the importance of using archaeological materials, especially animal remains, to study the long-term zoonotic potential of this disease, as only direct comparison of ancient human and animal species allows us to reconstruct potential transmission events over time.” -author Sarah Inskip from the University of Leicester, England.

Historical context of leprosy and its animal hosts

Leprosy is one of the oldest recorded diseases in human history and is still common in Asia, Africa and South America. Although scientists traced the evolutionary history of the mycobacterium that causes it, they did not know how it might have spread from animals to humans in the past, except for some hints that red squirrels in England may have served as hosts.

Details and results of the research

In the new study, researchers studied 25 human samples and 12 proteins to find out. M. leprae at two archaeological sites in Winchester. The city was known for its leprosarium (hospital for leprosy patients) and its connections with the fur trade. In the Middle Ages, squirrel fur was widely used for finishing and lining clothing. Many people also kept squirrels trapped in the wild as pets.

Researchers sequenced and reconstructed four genomes representing medieval strains M. lepraeIncluding the red protein genome. Analysis to understand their relationships revealed that they were all on the same branch of the family tree. M. leprae. They also showed a close relationship between the type of protein and the newly created strain isolated from the remains of a medieval human. They report that the medieval squirrel species was more closely related to human species in medieval Winchester than to modern squirrel species in England; This suggests that the infection circulated between humans and animals in the Middle Ages in a previously undetected way.

“The history of leprosy is much more complex than previously thought,” Schuenemann said. “The role that animals may have played in the transmission and spread of the disease in the past has not been taken into account, and therefore our understanding of the history of leprosy is incomplete until these hosts are taken into account. While this finding is important for understanding the present-day presence of the disease despite efforts to eradicate the disease, host animals are still taken into account.” “It is still valid today because it was not taken.”

“In the wake of COVID-19, host animals are now in the spotlight to understand disease emergence and persistence,” Inskeep said. said. “Our research shows that zoonotic diseases have a long history and that they have and continue to have a major impact on us.”