Ancient DNA Found in 1,000-Year-Old Gospel Reveals Sheep Disease History

Scientists have uncovered ancient DNA from the sheeppox virus within the pages of a 1,000-year-old gospel book, providing a surprising glimpse into the history of the disease. The discovery, announced by University College Dublin (UCD) in early September, utilized ancient DNA preserved in manuscripts to trace the evolution of the highly contagious virus.

The research, published in Science Advances, focused on the York Gospels. Researchers detected DNA of the sheeppox virus, which primarily affects sheep but does not infect humans, in the animal skins used to create the parchment. The York Gospels were penned by Anglo-Saxon scribes in the late 900s and have been housed at York Minster for centuries.

Scientists found traces of the sheeppox virus on parchment made from calfskin and goatskin. This suggests either cross-species infections or contamination during the parchment-making process. By comparing the manuscript DNA with genetic material recovered from Bronze Age sheep teeth, researchers determined that sheeppox has afflicted livestock for over 3,700 years.

UCD described the York Gospels as a "biological time capsule" that preserved evidence of the virus for centuries. The university stated that the research reveals sheeppox has threatened livestock for more than three and a half millennia.

Louis L'Hôte, the lead author of the study and a Ph.D. candidate at UCD, noted that the discovery demonstrates parchment's ability to preserve animal pathogen DNA for extended periods. "Archives and libraries around the world may also contain the genetic traces of disease outbreaks in animals in the past," L'Hôte said. "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."

L'Hôte added that the pathogen remains a threat today and that studying its ancient DNA could aid in developing strategies for its eradication. "People around the world are still fighting against this pathogen—there is currently an outbreak of sheeppox in Greece, causing much economic damage," he stated. "We find that unlike the smallpox virus, the sheeppox virus genome was very stable over the last few millennia." He suggested that genetic changes prior to this period might have been crucial to the sheeppox virus's evolution in infecting its host, offering potential insights for future control efforts.

The study of ancient DNA is increasingly shedding light on historical diseases. Earlier this year, smallpox DNA was discovered in centuries-old Chilean mummies, marking the first evidence of the disease in that region during the early colonial period. Separately, researchers at Yale analyzed DNA from a 16th-century Italian ruler, finding evidence that he died of malaria and helping to resolve a long-standing historical mystery.