Medieval Manuscripts Hold Sheep Virus DNA, Traced Back 3,700 Years
Sheeppox virus DNA turned up in medieval parchment such as the York Gospels, and Bronze Age sheep teeth push the disease back 3,700 years.
Researchers have recovered DNA from sheeppox virus in medieval parchment, including the 1,000-year-old York Gospels, and combined it with Bronze Age sheep teeth to show that the disease has infected livestock for more than 3,700 years. The work was led by University College Dublin (UCD) and announced in a UCD release published by ScienceDaily on Nov. 11.
Sheeppox is highly contagious. It can kill many animals in a flock, especially young sheep, and it cuts wool, meat and milk production.
How the team found virus DNA in books
Before paper was common, manuscripts were often written on prepared animal skins, including sheep, goat and cattle hides. The researchers say such skins can keep traces of infections the animal had when it died. They detected sheeppox DNA on several pages of a number of manuscripts, which indicates that infected animals supplied some of the skins.
Besides the York Gospels, the team studied the Corpus Glossary at Corpus Christi College Cambridge, described as one of the earliest English dictionaries, and other medieval manuscripts from Britain and continental Europe.
To go further back, the scientists examined DNA from Bronze Age sheep teeth found at ancient pastoralist settlements on the Eurasian steppe. Teeth can protect genetic material for thousands of years. These samples gave the oldest known genetic traces of the virus. The team then compared the ancient viral DNA with sequences from modern viruses.
What the comparison showed
The analysis suggests that the main branches of the capripoxvirus family, which includes sheeppox virus, goatpox virus and lumpy skin disease virus, split from one another between 11,500 and 3,700 years ago. The release notes that this window overlaps with the domestication of livestock and with the large-scale movement of sheep from the steppe into Europe.
The sheeppox genome changed very little over the past several thousand years. Lead author Louis L’Hôte, a PhD candidate at UCD, said the sheeppox genome was far more stable than that of the smallpox virus. He added that genetic changes before this stable period may have been important in how the virus came to infect sheep.
What is still unclear
Some viral DNA turned up on parchment made from calfskin and goatskin. Since sheeppox mainly infects sheep, the authors give two possible explanations: the virus occasionally infected other livestock, or the skins were contaminated during parchment production.
The publication status also needs care. The release says the study was published in Science Advances. Its reference line, however, cites a bioRxiv preprint (a paper posted before peer review) dated March 31, 2026, titled “3,500 years of sheeppox virus evolution inferred from archaeological and codicological genomes,” with the DOI 10.64898/2026.02.23.707469. The two statements differ, so the review status of the findings is unclear.
Why it matters
Libraries and archives may hold genetic traces of past animal disease outbreaks, according to the researchers. Dr. Kevin G. Daly, associate professor at the UCD School of Agriculture and Food Science and the study’s supervising author, said parchment preserves a record of livestock disease in the medieval period as well as cultural history.
Sheeppox is still a threat today. L’Hôte noted that “there is currently an outbreak of sheeppox in Greece,” causing economic damage.
The project involved specialists in genetics, history, virology, protein chemistry and conservation from more than 30 institutions, including Trinity College Dublin, the Helmholtz Institute for One Health, the University of Leicester, Cambridge University and the University of Copenhagen. Funding came from Taighde Éireann-Research Ireland and the European Research Council.
Source: ScienceDaily
