Analysis of animal DNA extracted from medieval manuscripts has allowed researchers to trace the nearly 4,000-year history of the sheeppox virus, according to a recently study published in Science Advances.
Sheeppox is a highly contagious disease that can spread rapidly throughout a flock, causing high mortality rates, as well as damaging wool, meat, and milk yields.
Among the works analyzed were the York Gospels, from the early Anglo-Saxon period, and the Corpus Glossary of Corpus Christi College Cambridge, one of the earliest English dictionaries.
In several cases, multiple pages from the same manuscript were found to contain sheeppox virus DNA, indicating that infected animals were used in their production.
“The recording of ancient DNA of pathogens has completely changed our understanding of infectious disease in the past, and here we show that parchment can also preserve animal pathogen DNA,” explained Louis L’Hôte, PhD candidate at University College Dublin (UCD) and lead author of the study. “It is possible that archives and libraries around the world also contain the genetic traces of disease outbreaks in animals in the past.”
“These genomes help us understand how these pathogens evolved and how they impacted past societies - such as sheeppox virus, which we show has been affecting Eurasian sheep herds for at least three and a half millennia.”
Cross-species infection or parchment contamination?
One of the most unexpected findings was the detection of sheeppox on parchment made from calfskin and goatskin, according to the study, suggesting that either a rare example of cross-species infection or contamination during the parchment-making process.
“Parchment making has been considered a vanishing craft, but we are beginning to understand just how much of the past it has retained,” said UCD School of Agriculture and Food Science Associate Professor Kevin G. Daly, who also serves as the study’s supervising author. This project shows that parchments not only preserve our cultural history for hundreds of years, but also the landscape of disease in our livestock in the medieval period.”
“This kind of exciting, surprising discovery is only possible when researchers from a range of disciplines come together to share their expertise and data - a generosity and trust that collaborative science depends on.”
Sheeppox around for over 3,700 years
Additionally, by combining the analysis of these medievial manuscripts alongside Bronze Age sheep teeth samples, researchers found that sheepox has been around for over 3,700 years.
By combining the study of manuscripts with even older samples from Bronze Age sheep teeth, the study reveals that Sheeppox has threatened livestock for over 3,700 years.
Unlike other skeletal material, teeth can preserve genetic evidence of infection over thousands of years, explained the study, in turn providing a valuable record of ancient outbreaks.
The earliest known detections of sheeppox virus came from livestock dental remains unearthed at ancient pastoralist settlements in the Eurasian steppe.
By comparing ancient and modern virus sequences, researchers were able to estimate that the sheeppox virus, goatpox virus, and lumpy skin disease virus, which all come from the same virus lineage, diverged between 11,500 and 3,700 years ago.
“People around the world are still fighting against this pathogen, there is currently an outbreak of sheeppox in Greece, causing much economic damage,” said L’Hôte.
“Ancient genomes can help us understand how these pathogens affecting us today evolved. We find that unlike the smallpox virus, the sheeppox virus genome was very stable over the last few millennia.”
L’Hôte added that the discovery may prove the importance of genetic changes before this point were crucial to how sheepox infects its hosts, “which may help us fight the pathogen in the future.”
The study was funded by Taighde Éireann-Research Ireland and the European Research Council, and led by University College Dublin, in collaboration with over 30 Irish and international institutions including Trinity College Dublin, the Helmholtz Institute for One Health, Université Paris 1 Panthéon-Sorbonne, the University of Leicester, Cambridge University, and the University of Copenhagen.