The story of a Medieval European plague is coming into focus through historic manuscripts, but not in the way you might think. Instead of providing mere historical accounts, the animal skins from which these Medieval volumes are constructed provide genetic evidence for reconstructing the 3,500-year story of the sheepox virus (SPPV), which decimated European livestock.
In a recent paper published in Science Advances, an international team of interdisciplinary researchers ranging from geneticists and virologists to historians and conservators explored the history of this pre-modern plague.
The new work combs through Medieval history to reveal the lineages of diseases plaguing modern herds, providing new insight into the viruses threatening modern animal agriculture.
Medieval Texts
Chosen for the work were some of the most important Medieval manuscripts that Europe has to offer, including the millennium-old York Gospels, one of the best surviving examples of an early Anglo-Saxon illuminated manuscript. Another work used in the study was one of the earliest known English dictionaries, the Corpus Glossary of Corpus Christi College, Cambridge. Beyond these notable examples, the team exploited a variety of English and continental European works.
Medieval volumes did not contain paper pages like modern books, but instead, vellum pages made of calfskin, as well as the skins of goats and sheep. Therefore, these works are preserved as hundreds-of-years-old biological specimens for modern geneticists.
SPPV tends to target younger animals, such as the calves from whom vellum is made, and is highly contagious, rapidly spreading through large portions of a herd. While these factors made the disease easier for modern researchers to study via vellum samples, it also made it devastating to wool, meat, and milk production.
Extracting DNA
“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. It is possible that archives and libraries around the world also contain the genetic traces of disease outbreaks in animals in the past,” said lead author Louis L’Hôte, PhD candidate at the University of Cambridge, Dublin.
“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,” L’Hôte added.
With the rapid spread of SPPV across herds, many manuscripts contained SPPV DNA on multiple pages within the same manuscript. Additionally, finding SPPV DNA on pages made from both calf and goat skin marks it as a rare example of cross-species infection.
“Parchment making has been considered a vanishing craft, but we are beginning to understand just how much of the past it has retained. 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,” said supervising author Dr Kevin G. Daly, Associate Professor at UCD School of Agriculture and Food Science.
“This kind of exciting, surprising discovery is only possible when researchers from a range of disciplines come together to share their expertise and data,” Day said, calling this “a generosity and trust that collaborative science depends on.”
Exploring Medieval DNA
The Medieval manuscripts combine with even older surviving biological records, such as teeth, to show the virus reaching back 3,700 years. Between the manuscripts and archaeological finds, the team identified 41 samples containing related viruses.
Along with the goatpox virus and the lumpy skin disease virus, SPPV belongs to a category called capripoxviruses. The new research allowed the team to compare the ancient and modern sequences to determine that the division between the various viruses in the group occurred between 3,700 and 11,500 years ago, around the time animal domestication took hold in Europe as sheep came off the steppe.
“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 concluded. “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 paper, “3,500 years of Sheeppox Virus Evolution Inferred from Archaeological and Codicological Genomes,” appeared in Science Advances on September 2, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.
