Archaeological evidence from medieval English sites in Winchester suggests that red squirrels served as hosts for strains of Mycobacterium leprae that caused leprosy in humans. Researchers from the University of Basel in Switzerland conducted genetic analysis on ancient animal remains and found that medieval red squirrels were the first known animal hosts of leprosy. The study also revealed that the medieval strain found in red squirrels was closely related to human strains from the same city, indicating an independent circulation of the disease between humans and squirrels during the Middle Ages.
The importance of involving archaeological material, such as animal remains, in studying the long-term zoonotic potential of diseases like leprosy was emphasized by the researchers. By comparing ancient human and animal strains, they were able to reconstruct potential transmission events across time. Leprosy, one of the oldest recorded diseases in human history, is still prevalent in parts of Asia, Africa, and South America. Understanding how the disease may have spread from animals to humans in the past is crucial for informing our knowledge of its evolutionary history.
The researchers studied 25 human and 12 squirrel samples from two archaeological sites in Winchester, a city known for its leprosarium and connections to the fur trade. Squirrel fur was widely used in the Middle Ages to trim and line garments, and many people kept squirrels as pets. By sequencing and reconstructing four genomes representing medieval strains of M. leprae, including one from a red squirrel, the researchers were able to show a close relationship between the squirrel strain and a human strain from medieval Winchester. This suggests that the infection was circulating between people and animals during the Middle Ages.
The discovery of a medieval strain of M. leprae in red squirrels adds a new layer of complexity to our understanding of the history of leprosy. The role of animals in the transmission and spread of the disease in the past has not been well considered, leading to an incomplete understanding of leprosy’s history. The researchers believe that this finding is relevant today, as animal hosts are still not widely considered in the study of diseases like leprosy, despite their potential significance in understanding the disease’s persistence over time.
In the context of the COVID-19 pandemic, the researchers point out that animal hosts are now becoming a focus of attention for understanding disease appearance and persistence. The long history of zoonotic diseases, as demonstrated by the findings of this study, highlights the significant impact that animals can have on human health. By studying the historical transmission of diseases like leprosy between humans and animals, we can gain valuable insights into how these diseases have evolved and persisted, even in the face of eradication efforts.
