The York Gospels, a 1,000-year-old manuscript housed at York Minster, has yielded an unexpected scientific find: traces of ancient sheeppox virus DNA preserved in its parchment pages.
The discovery was announced by University College Dublin (UCD) in early September and detailed in a study published in the journal Science Advances. Researchers used ancient DNA preserved in manuscripts and animal remains to trace thousands of years of evolution of the sheeppox virus, a highly contagious disease that affects sheep but is not known to infect humans.
The York Gospels were written in Canterbury in the late 900s by Anglo-Saxon scribes before being brought to York, where they have remained at York Minster for centuries. UCD described the manuscript as a “biological time capsule” that preserved evidence of the virus for centuries.
Researchers found sheeppox virus DNA not only on parchment made from sheepskin but also, unexpectedly, on parchment made from calfskin and goatskin — suggesting either cross-species infections or contamination during the parchment-making process.
By comparing the manuscript findings with DNA recovered from Bronze Age sheep teeth, the team determined that sheeppox has affected livestock for more than 3,700 years. UCD noted that teeth, unlike other skeletal material, can preserve genetic evidence of infection over thousands of years, offering a valuable record of past outbreaks.
“A highly contagious disease, sheeppox spreads rapidly and can affect large portions of a flock in a short time,” UCD said in a statement, adding that the disease is “particularly dangerous because it can cause very high mortality rates, especially in young animals, and dramatically reduce productivity by damaging wool, meat and milk yields.”
A document with wider implications
Louis L’Hôte, a Ph.D. candidate at UCD and lead author of the study, said the finding shows that parchment can preserve traces of animal pathogen DNA for centuries.
“It is possible that archives and libraries around the world also contain the genetic traces of disease outbreaks in animals in the past,” L’Hôte said. “These genomes help us understand how these pathogens evolved and how they affected past societies — such as sheeppox virus, which we show has been affecting Eurasian sheep herds for at least three-and-a-half millennia.”
L’Hôte said the pathogen remains a live concern, pointing to a current outbreak of sheeppox in Greece that he said is causing significant economic damage.
“We find that unlike the smallpox virus, the sheeppox virus genome was very stable over the last few millennia,” L’Hôte said. “This might mean that genetic changes before this point were very important to how the sheeppox virus evolved to infect its host, which may help us fight the pathogen in the future.”
The study adds to a growing body of research using ancient DNA to uncover the history of disease. Scientists earlier this year found smallpox DNA in centuries-old Chilean mummies, offering the first evidence of the disease in that part of South America during the early colonial period, while researchers at Yale found evidence that a 16th-century Italian ruler died of malaria.
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