Parchment from medieval manuscripts has yielded genetic evidence of sheeppox virus, giving researchers a new way to investigate the disease’s history among European livestock. The findings come from an international study led by University College Dublin and published in Science Advances.
The team recovered sheeppox virus DNA from animal skins used to make manuscripts including the approximately 1,000-year-old York Gospels. Other analyzed works included the Corpus Glossary of Corpus Christi College, Cambridge, described in the source as one of the earliest English dictionaries, along with medieval codices from Britain and continental Europe.
Because parchment was made from the hides of animals such as sheep, goats and cattle, it can retain biological evidence from the animal’s life or death. In several manuscripts, more than one page contained viral DNA. The researchers said this indicates that infected animals may have contributed skins for their production, although the presence of the virus on calfskin and goatskin could also reflect contamination during parchment manufacture or, possibly, uncommon cross-species infections.
The study reconstructed more than 3,500 years of sheeppox virus evolution. Sheeppox is highly contagious, can kill large numbers of animals—particularly young sheep—and can reduce wool, meat and milk production.
To extend the record beyond the medieval period, the researchers analyzed older samples from Bronze Age sheep teeth recovered at pastoralist settlements on the Eurasian steppe. The source describes these as the earliest known detections of sheeppox virus from dental remains. Teeth can preserve genetic evidence of infection over long periods, allowing the ancient sequences to be compared with those of modern viruses.
Those comparisons produced an estimated divergence window of 11,500 to 3,700 years ago for the major lineages of capripoxviruses: sheeppox virus, goatpox virus and lumpy skin disease virus. The researchers said this timing corresponds with the emergence of animal domestication and the movement of sheep from the steppe into Europe.
The team also found that the sheeppox virus genome remained relatively stable over the last several millennia, unlike the smallpox virus genome. According to lead author Louis L’Hôte, this stability could indicate that important genetic changes occurred earlier in the virus’s evolution. The researchers suggested that ancient genomes may help clarify how the pathogen developed and inform efforts to address its continuing effects on livestock.
