Evidence from archaeological sites in the medieval English city of Winchester shows that English red squirrels (red squirell, Sciurus vulgaris) once served as an important host for strains of Mycobacterium leprae that cause leprosy in humans.
“Thanks to our genetic analysis, we were able to identify squirrels as the first ancient animal host of leprosy,” says lead author Verena Schuenemann of the University of Basel. “”The medieval strain of bacteria from a squirrel that we managed to obtain is more closely related to the medieval human strains from the same city than to the strains isolated from infected modern squirrels. Overall, our results indicate an independent circulation of M. leprae strains between humans and squirrels during the medieval period.” In summary, it was found that the infection circulated between humans and animals in the Middle Ages in a manner not previously recognized.
Leprosy is one of the oldest recorded diseases in human history and is still widespread in Asia, Africa and South America. Although scientists traced the evolutionary history of the mycobacterium that causes it, they did not know how it could have spread from animals to humans in the past.
In the new study, researchers examined 25 human and 12 squirrel samples and looked for M. leprae at two archaeological sites in Winchester. This town was known in the Middle Ages for its leprosarium and its ties to the fur trade. In the Middle Ages, squirrel fur was widely used to trim clothing. Many people also caught wild squirrels as cubs in the wild and then kept them as pets.
The researchers sequenced and reconstructed four genomes representing medieval strains of M. leprae, including one from the red squirrel. An analysis to understand their relationships found that they all belong to the same branch of the M. leprae family tree. They also showed a close relationship between the squirrel strain and a newly formed strain isolated from medieval human remains.
Animal (inter)hosts of leprosy can be important even today, perhaps that is why the disease still persists despite all attempts to eradicate it.
“In the context of COVID-19 (note: but see also swine and bird flu etc.), animal hosts are now becoming a focus for understanding the emergence and persistence of disease,” adds co-author Sarah Inskip of the University of Leicester. “Our research shows that zoonoses have a long history and have had and continue to have a big impact on us.”
Ancient Mycobacterium leprae genome reveals medieval English red squirrels as animal leprosy host, Current Biology (2024). DOI: 10.1016/j.cub.2024.04.006. https://www.cell.com/current-biology/fulltext/S0960-9822(24)00446-9
Source: Cell Press / Phys.org, translated, shortened
Tags: People leprosy squirrels medieval England Sciencemag .cz
