In medieval England, leprosy spread between red squirrels and people, genome evidence shows
Evidence from archaeological sites in the medieval English city of Winchester shows that English red squirrels once served as an important host for Mycobacterium leprae strains that caused leprosy in people, researchers report May 3 in the journal Current Biology.
“With our genetic analysis we were able to identify red squirrels as the first ancient animal host of leprosy,” says senior author Verena Schuenemann of the University of Basel in Switzerland. “The medieval red squirrel strain we recovered is more closely related to medieval human strains from the same city than to strains isolated from infected modern red squirrels. Overall, our results point to an independent circulation of M. leprae strains between humans and red squirrels during the Medieval Period.”
“Our findings highlight the importance of involving archaeological material, in particular animal remains, into studying the long-term zoonotic potential of this disease, as only a direct comparison of ancient human and animal strains allows reconstructions of potential transmission events across time,” says Sarah Inskip of the University of Leicester, UK, a co-author on the study.
Leprosy is one of the oldest recorded diseases in human history and is still prevalent to this day in Asia, Africa, and South America. While scientists have traced the evolutionary history of the mycobacterium that causes it, they didn’t know how it may have spread to people from animals in the past beyond some hints that red squirrels in England may have served as a host.
In the new study, the researchers studied 25 human and 12 squirrel samples to look for M. leprae at two archaeological sites in Winchester. The city was well known for its leprosarium (a hospital for people with leprosy) and connections to the fur trade. In the Middle Ages, squirrel fur was widely used to trim and line garments. Many people also kept squirrels trapped wild squirrels as kits in the wild and raised them as pets.
The researchers sequenced and reconstructed four genomes representing medieval strains of M. leprae, including one from a red squirrel. An analysis to understand their relationships found that all of them belonged to a single branch on the M. leprae family tree. They also showed a close relationship between the squirrel strain and a newly constructed one isolated from the remains of a medieval person. They report that the medieval squirrel strain is more closely related to human strains from medieval Winchester than to modern squirrel strains from England, indicating that the infection was circulating between people and animals in the Middle Ages in a way that hadn’t been detected before.
“The history of leprosy is far more complex than previously thought,” Schuenemann said. “There has been no consideration of the role that animals might have played in the transmission and spread of the disease in the past, and as such, our understanding of leprosy’s history is incomplete until these hosts are considered. This finding is relevant to today as animal hosts are still not considered, even though they may be significant in terms of understanding the disease’s contemporary persistence despite attempts at eradication.”
“In the wake of COVID-19, animal hosts are now becoming a focus of attention for understanding disease appearance and persistence,” Inskip said. “Our research shows that there is a long history of zoonotic diseases, and they have had and continue to have a big impact on us.”
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This work was supported by the Swiss State Secretariat for Education, Research and Innovation SERI funded ERC Consolidator Project “RESERVOIR,” the University of Zurich’s University Research Priority Program “Evolution in Action: From Genomes to Ecosystems,” and the Fondation Raoul Follereau and the Heiser Program of the New York Community Trust for Research in Leprosy.
Current Biology, Urban, Blom, and Avanzi et al.: “Ancient Mycobacterium leprae genome reveals medieval English red squirrels as animal leprosy host.” https://www.cell.com/current-biology/fulltext/S0960-9822(24)00446-9
Current Biology (@CurrentBiology), published by Cell Press, is a bimonthly journal that features papers across all areas of biology. Current Biology strives to foster communication across fields of biology, both by publishing important findings of general interest and through highly accessible front matter for non-specialists. Visit http://www.cell.com/current-biology. To receive Cell Press media alerts, contact press@cell.com.
Evidence from archaeological sites in the medieval English city of Winchester shows that English red squirrels once served as an important host for Mycobacterium leprae strains that caused leprosy in people, researchers report May 3 in the journal Current Biology.
“With our genetic analysis we were able to identify red squirrels as the first ancient animal host of leprosy,” says senior author Verena Schuenemann of the University of Basel in Switzerland. “The medieval red squirrel strain we recovered is more closely related to medieval human strains from the same city than to strains isolated from infected modern red squirrels. Overall, our results point to an independent circulation of M. leprae strains between humans and red squirrels during the Medieval Period.”
“Our findings highlight the importance of involving archaeological material, in particular animal remains, into studying the long-term zoonotic potential of this disease, as only a direct comparison of ancient human and animal strains allows reconstructions of potential transmission events across time,” says Sarah Inskip of the University of Leicester, UK, a co-author on the study.
Leprosy is one of the oldest recorded diseases in human history and is still prevalent to this day in Asia, Africa, and South America. While scientists have traced the evolutionary history of the mycobacterium that causes it, they didn’t know how it may have spread to people from animals in the past beyond some hints that red squirrels in England may have served as a host.
In the new study, the researchers studied 25 human and 12 squirrel samples to look for M. leprae at two archaeological sites in Winchester. The city was well known for its leprosarium (a hospital for people with leprosy) and connections to the fur trade. In the Middle Ages, squirrel fur was widely used to trim and line garments. Many people also kept squirrels trapped wild squirrels as kits in the wild and raised them as pets.
The researchers sequenced and reconstructed four genomes representing medieval strains of M. leprae, including one from a red squirrel. An analysis to understand their relationships found that all of them belonged to a single branch on the M. leprae family tree. They also showed a close relationship between the squirrel strain and a newly constructed one isolated from the remains of a medieval person. They report that the medieval squirrel strain is more closely related to human strains from medieval Winchester than to modern squirrel strains from England, indicating that the infection was circulating between people and animals in the Middle Ages in a way that hadn’t been detected before.
“The history of leprosy is far more complex than previously thought,” Schuenemann said. “There has been no consideration of the role that animals might have played in the transmission and spread of the disease in the past, and as such, our understanding of leprosy’s history is incomplete until these hosts are considered. This finding is relevant to today as animal hosts are still not considered, even though they may be significant in terms of understanding the disease’s contemporary persistence despite attempts at eradication.”
“In the wake of COVID-19, animal hosts are now becoming a focus of attention for understanding disease appearance and persistence,” Inskip said. “Our research shows that there is a long history of zoonotic diseases, and they have had and continue to have a big impact on us.”
###
This work was supported by the Swiss State Secretariat for Education, Research and Innovation SERI funded ERC Consolidator Project “RESERVOIR,” the University of Zurich’s University Research Priority Program “Evolution in Action: From Genomes to Ecosystems,” and the Fondation Raoul Follereau and the Heiser Program of the New York Community Trust for Research in Leprosy.
Current Biology, Urban, Blom, and Avanzi et al.: “Ancient Mycobacterium leprae genome reveals medieval English red squirrels as animal leprosy host.” https://www.cell.com/current-biology/fulltext/S0960-9822(24)00446-9
Current Biology (@CurrentBiology), published by Cell Press, is a bimonthly journal that features papers across all areas of biology. Current Biology strives to foster communication across fields of biology, both by publishing important findings of general interest and through highly accessible front matter for non-specialists. Visit http://www.cell.com/current-biology. To receive Cell Press media alerts, contact press@cell.com.
JOURNAL
Current Biology
Current Biology
DOI
METHOD OF RESEARCH
Observational study
Observational study
SUBJECT OF RESEARCH
Not applicable
Not applicable
ARTICLE TITLE
Ancient Mycobacterium leprae genome reveals medieval English red squirrels as animal leprosy host
Ancient Mycobacterium leprae genome reveals medieval English red squirrels as animal leprosy host
ARTICLE PUBLICATION DATE
3-May-2024
3-May-2024
Lepra in the middle ages: New insights on transmission pathways through squirrels
IMAGE:
A LADY PLAYS WITH A PET SQUIRREL, WEARING A BELLED COLLAR, IN THE EARLY 14TH CENTURY LUTTRELL PSALTER.
view moreCREDIT: BRITISH LIBRARY BOARD MS ADD. MS 42130 F. 33R
Researchers at the University of Basel and the University of Zurich have been able to prove that British squirrels carried leprosy bacteria as early as the Middle Ages. Further results revealed a link between the pathogens found in the medieval rodents and those in the local human population during that period.
Skin spots, deformed noses, ulcers: leprosy, is an infectious disease that can bring about some serious symptoms. The bacterium responsible, Mycobacterium leprae, which still infects around 200,000 people each year especially in the Global South, also has a long history in Europe. The international research group led by paleogeneticist Professor Verena Schünemann (University of Basel, formerly University of Zurich) used archaeological findings to identify red squirrels (Sciurus vulgaris) as hosts for M. leprae in medieval England. The researchers also discovered that the leprosy bacteria in medieval squirrels were closely related to those isolated from medieval human skeletons from the same region. The results were published in the journal “Current Biology”.
From squirrels to humans or vice versa?
“This similarity shows us that leprosy bacteria were probably transmitted between animals and humans at that time,” says Schünemann. However, she stresses that, based on current knowledge, it is not clear how this took place. “We don’t know whether the squirrels infected humans or whether humans were the ones to introduce the disease to the animals,” says Schünemann.
There were certainly a number of points of contact between humans and squirrels during the Middle Ages. One key aspect was fur trade, which provided the highly sought-after squirrel fur for the upper echelons of society. Especially in the 11th and 12th centuries, for example, entire coats made of squirrel fur were produced for the various royal families. Furthermore, squirrels were also kept as pets, in royal courts as well as nunneries.
Genetic analysis from 20 milligrams
For their study, the researchers focused on the city of Winchester in southern England. The material necessary for the genetic analysis originates from two different archaeological sites within the city. The human remains were extracted from the location of a former leprosarium, a care facility specifically for people suffering from leprosy. The researchers were able to examine the medieval squirrels thanks to hand and foot bones found at a former skinner’s shop. “We carried out the genetic analyses on the squirrels’ tiny hand and foot bones, which weigh between 20 and 30 milligrams. That is not a lot of material,” explains Christian Urban, first author of the study.
For the researchers, the results are particularly important for predicting leprosy in the future. Because to this day, it is not completely clear how the disease spreads. “Our One Health approach prioritizes finding out more about the role animals played in the spread of diseases in the past”, says Schünemann. “A direct comparison between ancient animal and human strains enables us to reconstruct potential transmission events over time and helps to form conclusions about the long-term zoonotic potential of the disease”, she adds.
The results are therefore relevant for today, as animals still receive very little attention as hosts of leprosy, even though they may be important for understanding the current persistence of the disease despite all attempts to eradicate it.
JOURNAL
Current Biology
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Cells
ARTICLE TITLE
Ancient Mycobacterium leprae genome reveals medieval English red squirrels as animal leprosy host
ARTICLE PUBLICATION DATE
3-May-2024
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