A study in Winchester found that red squirrels in medieval England were important carriers of the leprosy-causing bacterium Mycobacterium leprae, showing a complex historical relationship between humans and animals in disease transmission, with implications for understanding zoonotic diseases today.
Research shows that medieval English red squirrels hosted leprosy-causing bacteria, impacting our understanding of disease history and its transmission between humans and animals.
Evidence from archaeological sites in medieval Winchester demonstrates that English red squirrels were once a significant host for Mycobacterium leprae strains that caused leprosy in people, as reported today in the journal Current Biology.
Genetic Analysis of Medieval Strains
“Through our genetic analysis, we identified red squirrels as the first ancient animal host of leprosy,” said Verena Schuenemann of the University of Basel in Switzerland. “The medieval red squirrel strain we found 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 an independent circulation of M. leprae strains between humans and red squirrels during the Medieval Period.”
“Our findings underscore the importance of incorporating archaeological material, specifically animal remains, into the study of the long-term zoonotic potential of this disease, as only a direct comparison of ancient human and animal strains allows reconstructions of potential transmission events over time,” said Sarah Inskip of the University of Leicester, UK, a co-author on the study.
Historical Background of Leprosy and Animal Hosts
Leprosy is one of the oldest known diseases in human history and continues to be present today in Asia, Africa, and South America. While scientists have traced the evolutionary history of the mycobacterium that causes it, they did not know how it may have spread to people from animals in the past beyond some indications that red squirrels in England may have served as a host.
Details of the Study and Its Findings
In the new study, the researchers examined 25 human and 12 squirrel samples from two archaeological sites in Winchester. The city was renowned for its leprosarium (a hospital for people with leprosy) and connections to the fur trade. In the Middle Ages, squirrel fur was widely used to adorn and line clothing. Many individuals also kept wild squirrels trapped as kits and raised them as pets. M. leprae The researchers sequenced and reconstructed four genomes representing medieval strains of
, including one from a red squirrel. An analysis to understand their relationships found that all of them belonged to a single branch on the M. lepraefamily tree. They also showed a close relationship between the squirrel strain and a newly constructed one isolated from the remains of a medieval person. They report that the medieval squirrel strain is more closely related to human strains from medieval Winchester than to modern squirrel strains from England, indicating that the infection was circulating between people and animals in the Middle Ages in a way that hadn’t been detected before. M. leprae “The history of leprosy is much more complicated than we thought before,” Schuenemann said. “No one has thought about how animals could have helped spread the disease in the past. Our understanding of leprosy’s history is not complete until we consider these hosts. This finding is important today because we still don't consider animal hosts, even though they may be important for understanding why the disease continues to exist despite efforts to get rid of it.”
“After COVID-19, people are now paying more attention to animal hosts to understand how diseases appear and persist,” Inskip said. “Our research shows that zoonotic diseases have had and continue to have a big impact on us.”
Reference: “Ancient Mycobacterium leprae genome reveals medieval English red squirrels as animal leprosy host” 3 May 2024,
Current Biology DOI: 10.1016/j.cub.2024.04.006.
Research shows that leprosy-causing bacteria was hosted by medieval English red squirrels, which changes our understanding of disease history and how it spreads between humans and animals. Evidence from archaeological…
