Squirrels, vectors of leprosy during the Middle Ages

Health

#Squirrels #vectors #leprosy #Middle #Ages

Evidence collected from medieval archaeological sites in the English town of Winchester reveals that red squirrels once served as a breeding ground for strains of Mycobacterium leprae having caused leprosy among citizens, researchers write in Current Biology.

“With our genetic analysis, we were able to identify that red squirrels were the first animal host of leprosy,” mentions the main author of the study, Verena Schuenemann, from the University of Basel, in Switzerland.

“The medieval red squirrel-related strain we recovered is more closely related to human strains, present in the same town, than to strains from modern-day red squirrels. Ultimately, our results show an independent circulation of M. leprosy between humans and red squirrels during the medieval period. »

Leprosy is one of the oldest diseases in human history, and is still present today, particularly in Asia, Africa and South America. Although researchers have traced the history of the evolution of the mycobacterium that causes it, we still did not know how the disease had spread from animals to humans in the past, with the exception of a few clues that the disease Red squirrel, in the United Kingdom, may have served as a host.

As part of the study, the researchers studied 25 human samples and 12 squirrel samples, in an attempt to detect traces of M. leprosy, at two archaeological sites in Winchester. During the Middle Ages, the town was well known for its leper hospitals, in addition to its connections with other fur suppliers and traders.

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During this time, moreover, squirrel hair was often used inside clothing. Several residents also had squirrels, after trapping wild animals.

After having sequenced and reconstructed four genomes representing as many medieval strains of M. leprosy, including one that came from a red squirrel. Further analysis revealed that not only were these strains all related, but the one linked to the squirrel was the same one that was also found in the remains of a local resident at the time.

The researchers also specify that the strain of the red squirrel, in the Middle Ages, was more closely related to the strain detected in humans living in Winchester, at this period of history, than the strains that we find today in British squirrels. This, it is written, indicates that the infection circulated between animals and humans in medieval times, and in a way that had not been detected until now.

“The history of leprosy is much more complex than we believed,” emphasized Ms. Schuenemann. “We have not considered the role that animals may have played in transmitting disease in the past, and so our understanding of the history of leprosy is incomplete until we consider account of these hosts. »

“In the wake of COVID-19, animal hosts are attracting attention when it comes to understanding the appearance and persistence of diseases,” said Sarah Inskip, co-author of the study attached to the University of Leicester.

“Our study demonstrates that there is a long history of zoonotic diseases (linked to animals, editor’s note), and that they have had, and continue to have, a great impact on us. »

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