Researchers report that evidence from archaeological sites in medieval Winchester, England, indicates that English red squirrels were once a significant host for Mycobacterium leprae strains, which caused leprosy in humans. The findings were published in the journal Current Biology on May 3.”The senior author, Verena Schuenemann from the University of Basel in Switzerland, stated that 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. Our results indicate an independent circulation of M. leprae strains between humans and red squirrels during the Medieval Period,” she said. She emphasized the significance of incorporating archaeological material, especially animal remains, into studying the long-term zoonotic potential of the disease.According to Sarah Inskip of the University of Leicester, UK, who co-authored the study, analyzing ancient human and animal strains can help us understand how leprosy may have been transmitted over time. Leprosy has been a known disease for centuries and is still a problem in Asia, Africa, and South America. Although scientists have studied the evolutionary history of the mycobacterium that causes leprosy, they were unsure how it spread from animals to humans in the past. Some evidence suggested that red squirrels in England may have played a role in the transmission of the disease. In this new study, researchers examined 25 human samples and 12 squirrel samples.The researchers conducted a study to search for M. leprae at two archaeological sites in Winchester. The city was famous for its leprosarium, a hospital for people with leprosy, and its ties to the fur trade. During the Middle Ages, squirrel fur was commonly used to trim and line clothing. Additionally, many individuals would capture wild squirrels and raise them as pets.
The team sequenced and reconstructed four genomes that represented medieval strains of M. leprae, including one from a red squirrel. An analysis was conducted to understand their relationships and it was discovered that all of them belonged to a single branch on the M. leprae family.tree. The researchers found a strong connection between the squirrel strain and a newly discovered strain isolated from the remains of a medieval individual. They discovered that the medieval squirrel strain is more closely related to human strains from medieval Winchester than to modern squirrel strains from England. This indicates that the infection was circulating between people and animals in the Middle Ages in a way that had not been previously detected.
“The history of leprosy is much more intricate than we previously believed,” Schuenemann noted. “There has been little consideration of the potential role that animals may have played in the transmission and spread of the disease.”The history of leprosy has been incomplete because animal hosts have not been considered in the past. Understanding the role of animal hosts is important, as they may play a significant role in the persistence of the disease despite efforts to eradicate it. The focus on animal hosts in understanding disease appearance and persistence has increased in the wake of COVID-19. Research shows that zoonotic diseases have had a long history and continue to have a significant impact on humans.
