An international team of multidisciplinary researchers has unlocked a groundbreaking biological archive, revealing that some of Europe’s most revered historical manuscripts—including the thousand-year-old York Gospels—serve as unexpected time capsules for tracing the evolutionary history of the sheeppox virus (SPPV). By extracting ancient pathogen DNA from the animal skins utilized to craft medieval parchment, scientists have successfully mapped more than three and a half millennia of agricultural history, offering unprecedented insights into a devastating livestock disease that continues to threaten modern farming economies.
Published in the scientific journal Science Advances, the landmark study was spearheaded by a diverse collective of geneticists, historians, virologists, protein chemists, and conservators based at University College Dublin (UCD) in Ireland. Their findings not only rewrite the temporal boundaries of capripoxvirus evolution but also establish libraries and archives worldwide as untapped epidemiological resources capable of shedding light on ancient animal health and human-animal interactions.
Unlocking the Secrets of Medieval Parchment
Parchment, the ubiquitous writing material of medieval Europe, has long been prized for its remarkable durability, preserving cultural texts, religious liturgy, and administrative records for centuries. However, its biological origin—derived from the processed hides of livestock such as sheep, goats, and calves—has transformed these cultural artifacts into molecular archives. When scribes prepared these skins during the Middle Ages, cellular material from the animal, including any systemic pathogens present at the time of slaughter, was inadvertently trapped and preserved within the collagen matrix.
By harvesting minute samples from the margins and bindings of several notable medieval codices, the UCD-led research team recovered genetic fragments of the sheeppox virus. Among the artifacts analyzed was the York Gospels, a magnificent illuminated manuscript dating back to the early Anglo-Saxon period that has served as a cornerstone of English ecclesiastical history for a millennium. Researchers also identified viral DNA within the Corpus Glossary housed at Corpus Christi College, Cambridge—widely recognized as one of the earliest English dictionaries—alongside various other medieval manuscripts originating from across Britain and continental Europe.
In several instances, genetic sequencing revealed viral traces spanning multiple pages of the same manuscript, confirming that these documents were manufactured using hides from flocks actively besieged by the disease. Intriguingly, the detection of sheeppox virus DNA on parchment traditionally attributed to calfskin and goatskin points toward rare historical cross-species spillover events or potential cross-contamination during the intensive medieval parchment-making workshops.
A Chronology of Conflict: Tracing 3,700 Years of Sheeppox
To contextualize the findings extracted from medieval manuscripts, the research team pushed their temporal window even further back by analyzing ancient skeletal remains. By examining Bronze Age sheep teeth recovered from archaeological sites across the Eurasian steppe, the scientists secured foundational genetic data that extended the documented timeline of the virus.
Unlike porous bones, dental enamel acts as a robust natural vault, shielding ancient DNA from environmental degradation over millennia. The detection of sheeppox virus signatures in these ancient dental remains allowed researchers to establish a comprehensive evolutionary timeline. Through comparative genomic analysis of ancient viral strains and their modern descendants, the team estimated that major lineages of capripoxviruses—encompassing the sheeppox virus, goatpox virus, and lumpy skin disease virus—diverged between 11,500 and 3,700 years ago.
This expansive evolutionary timeline correlates closely with pivotal milestones in human prehistory: the intensification of early animal domestication and the large-scale migration of pastoralist sheep populations from the Eurasian steppe westward into Europe. As human societies transitioned from nomadic pastoralism to settled agricultural communities, dense livestock populations provided an ideal transmission environment, allowing virulent pathogens to establish permanent footholds within early farming economies.
The Economic and Agricultural Impact of Sheeppox
Sheeppox remains one of the most formidable and highly contagious viral threats facing modern ovine agriculture. The disease spreads rapidly through direct contact, aerosol transmission, and contaminated equipment, capable of sweeping through naive flocks with devastating swiftness. Characterized by high fever, respiratory distress, and generalized cutaneous lesions, SPPV frequently results in mortality rates approaching 50 percent, particularly among lambs and immunologically vulnerable animals. Beyond direct mortality, survivors often suffer from permanently compromised productivity, resulting in severe economic devaluation of wool, meat, and dairy yields.
The resonance of this historical research is underscored by contemporary outbreaks. Modern farming communities across regions of Europe, the Middle East, and Asia continue to combat the pathogen. Recent outbreaks in countries such as Greece have demonstrated that the virus remains an active economic hazard, capable of triggering strict quarantine measures, international trade restrictions, and massive culling operations to prevent regional contagion.
Perspectives from the Research Front
The integration of molecular biology and historical codicology represents a paradigm shift in how researchers approach ancient disease ecology. Louis L’Hôté, a PhD candidate at University College Dublin and lead author of the study, emphasized the transformative potential of pathogen ancient DNA (aDNA).
"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," L’Hôté stated. "It is possible that archives and libraries around the world also contain the genetic traces of disease outbreaks in animals in the past. 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."
Reflecting on the unexpected stability of the viral genome, L’Hôté noted a striking contrast to other human-centric pathogens. "We find that unlike the smallpox virus, the sheeppox virus genome was very stable over the last few millennia," he explained. "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."
Dr. Kevin G. Daly, Associate Professor at the UCD School of Agriculture and Food Science and supervising author of the study, highlighted the interdisciplinary nature of the discovery. "Parchment making has been considered a vanishing craft, but we are beginning to understand just how much of the past it has retained," said Daly. "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. This kind of exciting, surprising discovery is only possible when researchers from a range of disciplines come together to share their expertise and data—a generosity and trust that collaborative science depends on."
Broader Implications for Science and Conservation
The successful extraction of viable pathogen genomes from cultural heritage artifacts opens new frontiers for paleomicrobiology. By demonstrating that archival documents function as biological repositories, the UCD study paves the way for retrospective surveillance of other historic epizootics, such as rinderpest and foot-and-mouth disease, which similarly devastated historical European agriculture.
Furthermore, this methodological framework bridges a historical gap between archaeology and virology, providing contemporary epidemiologists with deep-time evolutionary data. Understanding the long-term mutation rates, host adaptation mechanisms, and environmental resilience of capripoxviruses offers critical baseline intelligence for vaccine development, biosecurity protocols, and disease eradication strategies in the 21st century. As researchers continue to probe the silent archives of medieval libraries, history and science converge, proving that the parchment pages of the past hold vital keys to securing the agricultural future.
