Red squirrels in the British Isles are infected with leprosy bacteria

Microbiologists at EPFL and the University of Edinburgh have discovered that red squirrels in Britain and Ireland carry the two bacterial species that cause leprosy in humans. Once rampant in medieval Europe, leprosy dramatically declined by the end of the Middle Ages for reasons that are still unclear. About a century ago, leprosy in Europe virtually disappeared, at least among humans. Examining diseased red squirrels from England, Ireland, and Scotland, scientists at EPFL and the University of Edinburgh have now discovered that the same bacteria that cause leprosy in humans also infect red squirrels. Leprosy is an infectious disease that mainly affects the skin, peripheral nerves, the upper respiratory tract, and the eyes. It is caused by the bacteria Mycobacterium leprae and the recently discovered Mycobacterium lepromatosis. One of the most ancient diseases, leprosy has had an enormous social impact across multiple cultures throughout history.