Leprosy in Medieval Squirrels

AAAS: " In medieval England, leprosy bounced between humans + squirrels." Enzootic is a term referring to an infectious disease prevalent in a wild animal population, which in the right circumstances can 'spill over' to a human population. "Leprosy, which can be caused by two bacterial species—Mycobacterium leprae and M. lepromatosis—is on the decline but still afflicts more than 200,000 people each year, mostly in Asia, Africa, and South America." The most common spread requires prolonged contact with an infected person. For centuries, in fact, it was assumed to be a disease only of Homo sapiens, but in the 1970s M. leprae was discovered in 'nine-banded armadillos in North and South America—which occasionally pass it on to people—and in a few nonhuman primate species.' Then in 2016, "scientists also discovered that red squirrels (Sciurus vulgaris) in England carry a strain of M. leprae that’s closely related to the one that circulated among medieval English humans." Sarah Inskip, an osteoarchaeologist at the University of Leicester, was an author of a new study perhaps explaining the link. "Middle Ages England was squirrel crazy: People kept the arboreal rodents as pets and used their furs to line and trim clothing." The researchers 'zeroed in on the medieval city of Winchester, which had not only skinners, tailors, and furriers, but also a hospital for leprosy patients.' Working in a pit in Winchester, 'the team identified 12 red squirrel bones from between the 10th and 13th centuries that appeared swollen, rough, or damaged from infection or inflammation, the markers of leprosy.' Working with these bones, they managed to reconstruct a genome of a M. leparae strain. "To the team’s surprise, the medieval squirrel strain bore an even closer relation to medieval human strains gathered from the site of the leprosy hospital than to those taken from modern red squirrels." Gotta say this is excellent sleuthing. But it also takes me back to a pet squirrel I had in about the fourth grade, a youngster who had apparently fallen out of a nest. No leprosy involved of course. [No, not my photo. This squirel has a British accent].