Scientists recently discovered traces of an ancient disease in an unlikely place: the pages of a 1,000-year-old gospel book.
The discovery, which centered on the York Gospels, was announced by University College Dublin (UCD) in early September.
In a study recently published in Science Advances, UCD researchers traced thousands of years of evolution of the sheeppox virus using ancient DNA preserved in manuscripts and animal remains.
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The highly contagious disease affects sheep but is not known to infect humans. Researchers detected its DNA in the animal skins used to make parchment, according to the university.
The York Gospels were written in Canterbury in the late 900s by Anglo-Saxon scribes and were later brought to York Minster — where they've been housed for centuries.
Unexpectedly, researchers found traces of sheeppox virus on parchment made from calfskin and goatskin, suggesting either cross-species infections or contamination during the parchment-making process.
Comparing the manuscripts with DNA recovered from Bronze Age sheep teeth, researchers found that sheeppox has plagued livestock for over 3,700 years.
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In a statement, UCD described the York Gospels as a "biological time capsule" that preserved evidence of the virus for centuries.
"The research reveals that sheeppox has threatened livestock for more than 3,700 years," the university said.
"Unlike other skeletal material, teeth can preserve genetic evidence of infection over thousands of years, providing a valuable record of past outbreaks."
Sheeppox can spread rapidly through flocks and can be deadly, particularly for young animals — making outbreaks a potentially serious threat to livestock-dependent communities.
"A highly contagious disease, sheeppox spreads rapidly and can affect large portions of a flock in a short time," UCD said.
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"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."
Louis L'Hôte, a Ph.D. candidate at UCD who was the lead author of the study, told university officials that the discovery shows 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," said L'Hôte.
"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."
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L'Hôte added that the pathogen remains a threat today — and that studying its ancient DNA could help researchers better understand how to eradicate it.
"People around the world are still fighting against this pathogen — there is currently an outbreak of sheeppox in Greece, causing much economic damage," he said.
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"We find that unlike the smallpox virus, the sheeppox virus genome was very stable over the last few millennia," he added.
"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," he added.
Fox News Digital reached out to L'Hôte for further comment and insight.
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A growing number of ancient DNA discoveries have shed new light on diseases that afflicted humans and animals centuries ago.
Earlier this year, scientists discovered smallpox DNA in centuries-old Chilean mummies — providing the first evidence of the disease in that part of South America during the early colonial period.
At Yale, researchers analyzed ancient DNA from a 16th-century Italian ruler and found evidence that he died of malaria, helping resolve a centuries-old mystery surrounding his sudden death.