Medieval Englishmen loved squirrels

A beautiful coat and a personality to be jealous of; The English used to have a lot of fun with squirrels. That love has probably been fatal for many; new research shows that squirrels could carry deadly diseases.

In medieval England it certainly was; squirrels looked cute and they had fur that was perfect as a detail on a garment. Swiss researchers have now revealed that this preference harbored a deadly secret: squirrels used to be able to… Mycobacterium leprae which can cause leprosy, also known as leprosy. The medieval version of M. leprae at the time, the variant for squirrels was very similar to the variant that was also contagious to humans, which ultimately led to a circular effect in which people and squirrels kept each other infected. Scientist Verena Schuenemann contributed to the research. She says: “With our genetic analysis, we have been able to prove that red squirrels were one of the first animal species capable of being a host for leprosy.” The research has been published in the journal Current Biology.

Leprosarium
For the research, the scientists used two archaeological sites, both located in Winchester, in the south of England. The first archaeological site is located in a place that used to be a hotspot for leprosy patients, because it was here in the Middle Ages St Mary Magdalen Leprosarium stood – which, in short, is a hospital that specialized in leprosy. The second archaeological site is called Staple Gardens and is located more towards the center of the city. In total, the researchers studied the remains of 25 people and 12 squirrels by taking samples and analyzing them afterwards in the lab.

This analysis showed that all were found in humans and squirrels M. lepraebacteria came from the same family branch. The same analysis also showed a close link between the samples taken from the squirrels and a new variant that appeared isolated in the remains of a human. The results show that the medieval leprosy variants of squirrels were very similar to the variants that also affected people at the time – and therefore a lot less similar to modern leprosy variants that can currently be found among squirrels.

Sickening animals
According to the scientists, the results are significant because they show that the spread of leprosy was ultimately a lot more complicated than previously thought. Schuenemann explains: “The history of leprosy is a lot more complex than we previously thought. In the past, we never considered the fact that animals can also transmit leprosy. This means that our understanding of the history of leprosy is incomplete until we also consider this possibility. This conclusion is still relevant today, because in science we do not often look at animals as possible spreaders of diseases – despite the fact that this could still be an important reason why diseases sometimes persist for so long.”

Co-researcher Sarah Inskip also contributed to the study. She concludes: “Our results show how important it is to also include archaeological material during an investigation – especially animal remains. Only a direct comparison between different samples from ancient human and animal remains can sometimes explain why some dispersal events occurred over time. In the wake of COVID-19, we are slowly but surely starting to look more and more at animals as a possible source of spread for some diseases. Our research has shown that the world has a long history of diseases ultimately spreading in this way.”