Sheeppox is a highly contagious, often fatal viral disease that was largely eradicated from much of European livestock in the 20th century. But there is still the occasional regional outbreak, such as the one that afflicted many flocks of sheep in Greece last year. In order to reconstruct how the virus has evolved over the last 3,500 years, scientists extracted and sequenced sheeppox DNA preserved in the animal skins used for the parchment of numerous medieval manuscripts.
They reported their findings in a new paper published in the journal Science Advances. It is possible that archives and libraries around the world also contain the genetic traces of disease outbreaks in animals in the past,” said co-author Louis L’Hôte, a graduate student at University College Dublin. There are more frequent mentions of deadly outbreaks of “pockes” or “variola” in sheep by the Middle Ages, recorded in various agricultural texts and accounting documents in France, Spain, and England.
There seemed to be a decline in outbreaks in 17th-century France, although frequent outbreaks re-emerged in the 18th and 19th centuries, often with high mortality rates in the flocks. Great Britain did not experience a sheeppox resurgence until 1847. However, very little was known about the genetic history of the sheeppox virus.
That’s why L’Hôte et al. turned to analyzing DNA in medieval manuscripts—the parchments were often made from sheep leather. A number of analytical techniques have emerged in recent decades to help create these kinds of historical molecular records.
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