Red squirrels caused leprosy among the medieval English

Red squirrels caused leprosy among the medieval English

One side effect of the Covid pandemic is a renewed interest in so-called zoonotic diseases. They are infectious diseases that can be transmitted between animals and humans through direct or indirect contact. Scientists are beginning to look back in time and at conditions about which there is still uncertainty. For example, leprosy is one of the oldest recorded diseases in human history, and outbreaks continue today in Asia, Africa, and South America. As with the coronavirus, leprosy bacteria are transmitted from person to person through the air through coughing and sneezing.

The evolutionary history of this Mycobacterium leprae Which causes infectious skin and nerve diseases is already known. But what about the possibility of transmission from humans to animals as the beginning of an outbreak? What is the animal, if any?

The knowledge available so far, in brief, boils down to this. Four animals can carry leprosy bacteria and become ill: two species of monkeys (mangabey and chimpanzee), nine-banded armadillos, and squirrels. It is estimated that transmission of the disease from animals to humans is “possible by chance,” and there is still no evidence that animals constitute a significant transmission agent on a global scale. Archaeological research now sheds a different light on this matter.

Contagious pet

A team led by paleontologist Verena Schuenemann (University of Basel) identified two sites in Winchester. In the Middle Ages, this English city was a famous home to lepers and a center for the animal skin trade. Including red squirrel, which was often used by tailors for decorative borders and lining. Wild squirrel babies have also been captured and used as pets.

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Comparative genetic and other research conducted on 25 samples of human remains and twelve squirrel remains led the team down an interesting path. The team successfully identified the red squirrel as the first, and therefore oldest, animal host of leprosy bacteria. More controversially, according to the team, the research also suggests the existence of a medieval “leper circle” in which bacteria jumped from the red squirrel to humans.

What overall conclusions do researchers draw from this? This archaeological research can, first, contribute to a better understanding of contemporary epidemics and their zoological history. Knowledge of this context can in turn lead to better prevention and treatment – in this case in very specific terms – of leprosy.

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