Lesions on the limbs, nose, and ears of red squirrels were recently observed in Scotland, leading to the discovery that the squirrels were infected with leprosy. The squirrels in question were infected with the more recently discovered form of leprosy caused by the Mycobacterium lepromatosis bacterium that has also been the cause of human cases in Mexico.
After the initial discovery, squirrels across the UK were checked and those living in Dorset were also found to be suffering from leprosy. They were infected with the medieval form caused by the Mycobacterium leprae bacterium, showing that the bacterium causing leprosy varies based on geography.
The last known case of leprosy in the United Kingdom was in 1789 and it was thought to have been completely eradicated at that time. Scientists are now interested in knowing if rodents, such as squirrels, aided in the spread of leprosy during medieval times and if they have been carriers of the disease for centuries. If so, this could aid current human populations still struggling to eradicate the disease.
The red squirrel is currently endangered across Eurasia and how the disease is spreading between squirrels is unclear; however, scientists do not think it is harming the overall population size. Leprosy is spread in humans from coughing and sneezing, so scientists are unsure how to spreads from squirrel to squirrel, but hypothesize it might spread from close contact, such as when multiple squirrels gather at a feeder. Scientists do not believe the risk of these squirrels spreading leprosy to humans is high, especially in developed countries like the UK, but this may be more of a problem in areas where humans come in contact with rodents everyday. People are urged to wear gloves and wash their hands if they find and handle a dead red squirrel.