Medieval manuscripts reveal 3,700-year history of deadly sheep pox virus

During the Middle Ages, much of Europe’s written material was produced on the skins of sheep, goats and cattle, which were processed into parchment. Scientists have now extracted DNA from this centuries-old material, finding traces of sheep pox virus that offer new clues to the evolution of the disease and its impact on livestock and past societies.

An international team of geneticists, historians, virologists, protein chemists and conservators, led by scientists at University College Dublin, analysed parchment from historic manuscripts, including the 1,000-year-old York Gospels, one of the finest illuminated manuscripts to survive from the late Anglo-Saxon period. The researchers also examined earlier works, including the Corpus Glossary at Corpus Christi College in Cambridge, regarded as one of the earliest English dictionaries, as well as medieval texts from across Britain and continental Europe, according to the latest report by Euronews.

“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,” said Louis L’Hôte, the study’s lead author.

The researchers said it was possible that archives and libraries around the world could contain genetic traces of past disease outbreaks among animals.

Sheep pox is a highly contagious viral disease that can spread rapidly through a flock, causing fever, skin lesions and death. It can inflict substantial economic losses through reduced milk production, damage to hides and wool, and trade restrictions. There is no evidence that sheep pox infects humans.

The study, published in Science Advances, found that in some cases several pages from the same manuscript contained sheep pox virus DNA, suggesting that infected animals had been used to produce the parchment. Researchers also found traces of the virus on parchment made from calfskin and goatskin, which may indicate cross-species infection or contamination during the parchment-making process.

By combining DNA recovered from the manuscripts with older samples taken from Bronze Age sheep teeth, the researchers concluded that sheep pox had been threatening livestock for more than 3,700 years.

“Ancient genomes can help us understand how these pathogens affecting us today evolved. We find that unlike the smallpox virus, the sheep pox 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 sheep pox virus evolved to infect its host, which may help us fight the pathogen in the future.”

By Tamilla Hasanova