Medieval Winchester, England, likely saw a surge in leprosy cases due to the local red squirrel population, according to new research from a team of archaeologists and geneticists. The study examined remains from two archaeological sites within the city, revealing a close genetic link between leprosy strains found in both humans and squirrels.
Leprosy, formally known as Hansen’s disease, is a highly contagious bacterial infection that can lead to nerve damage, paralysis, and blindness if left untreated. According to the Centers for Disease Control and Prevention (CDC), the primary cause is Mycobacterium leprae, a bacterium that infects several species, including humans, nine-banded armadillos, and red squirrels.
Published in Current Biology, the study analyzed 25 human samples and 12 squirrel samples from two Winchester sites. This analysis allowed researchers to reconstruct four medieval M. leprae genomes, one of which originated from a red squirrel. Winchester, located in Hampshire, rose to prominence as the capital of Wessex in 871 AD, during the reign of King Alfred the Great.
Red Squirrels as a Leprosy Vector
One of the key sites investigated was St Mary Magdalen’s leprosarium, a hospital dedicated to leprosy patients. The research team discovered a striking genetic similarity between the bacterial strains found in the squirrels and the human remains. “Our genetic analysis pinpointed red squirrels as the first ancient animal host of leprosy,” explained Verena Schuenemann, an archaeologist at the University of Basel and the study’s senior author. “The medieval red squirrel strain we identified is more closely related to medieval human strains from Winchester than to strains isolated from infected modern red squirrels.”
Medieval depiction of a squirrel.Medieval depiction of a squirrel. Photo: Andy Soloman/UCG/Universal Images Group (Getty Images)
Schuenemann, specializing in ancient pathogen genomics, highlighted the study’s significant finding: the bacterial strain in medieval squirrels is genetically closer to some of the strains found in medieval Winchester residents than to those present in modern red squirrels.
Squirrel-Human Interaction in Medieval England
During the medieval period, red squirrels were commonly kept as pets in England. Their fur was also a highly sought-after material for garments across Europe, including England, where it was imported through trade. English customs records from 1384 reveal a stark contrast: while approximately 15,000 other animal skins were imported, a staggering 377,200 squirrel skins entered the country. This extensive trade in squirrel fur potentially facilitated the spread of leprosy.
Transmission and Implications
While definitive proof of direct transmission remains elusive, the close genetic relationship between the squirrel and human strains, coupled with their co-existence in Winchester during the same period, strongly suggests cross-species infection.
The study’s authors emphasize the broader implications of their findings: “This research, combined with recent discoveries of leprosy in modern wild armadillos in the Americas, wild red squirrels in the UK, and potential insect vectors, should prompt a more serious consideration of animal reservoirs in the persistence of leprosy today.”
Zoonotic diseases, like COVID-19, continue to pose a significant threat to human health. The current concern surrounding H5N1 avian influenza, which has been detected in goats, cows, and humans, underscores the importance of understanding disease transmission. Studying historical cases, such as the leprosy outbreak in medieval Winchester, provides valuable insights into how diseases spread between species.
Conclusion
The study’s findings highlight the likely role of red squirrels in the spread of leprosy in medieval Winchester. This research underscores the importance of considering animal reservoirs in the transmission and persistence of infectious diseases, both past and present. The continued study of historical outbreaks can contribute significantly to our understanding and management of present-day zoonotic threats.
