Scientists have found traces of an ancient virus in medieval manuscripts
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- Scientists have found traces of an ancient virus in medieval manuscripts
Ancient books can store not only evidence of the culture and daily life of past eras, but also traces of diseases that affected animals thousands of years ago. Researchers have discovered the genetic material of the sheep pox virus in the parchment of medieval manuscripts and reconstructed the history of the spread of the infection. The fact that ancient books told scientists about the evolution of a dangerous pathogen is in the Izvestia material.
Sheep pox is a highly contagious viral disease that affects sheep and is characterized by fever, nodules and rashes on the skin and mucous membranes. The infection is transmitted mainly by airborne droplets and through contact with infected animals or objects. The disease can lead to sheep deaths, decreased productivity, and significant economic losses in livestock production. The pathogen belongs to the genus Capripoxvirus. The sheep pox virus poses no danger to humans.
The manuscripts preserved the DNA of the virus
An international team led by specialists from University College Dublin studied medieval manuscripts and found traces of the sheep pox virus (SPPV) in the parchment. The results of the study are published in the journal Science Advances. Scientists have obtained 21 new ancient genomes of the pathogen, and in total they analyzed 39 archaeological and historical samples.
Among the documents studied are the York Gospels, created about 1 thousand years ago, as well as the Corpus Glossary— one of the earliest English dictionaries dating from about the 9th century. Viral DNA has also been found in other manuscripts from Britain and continental Europe.
Before the widespread use of paper, parchment, specially treated animal skin, was used to make books. If an animal was infected, the genetic material of the pathogen could be preserved in its skin and centuries later fall into the hands of researchers. Unexpectedly, the virus's DNA was also found on calfskin and goat skin parchment. Scientists admit that this could be due to infection of other animal species or contamination of the material during processing of hides.
The parchment became an archive of ancient epidemics
The discovery of viral DNA in manuscripts opens up a new way to study the history of infections. Until now, scientists have mainly been looking for traces of ancient pathogens in the remains of humans and animals. Now it has become clear that objects created from biological materials can also become a source of information.
Louis L'aut, lead author of the study
Recording ancient pathogen DNA has completely changed our understanding of infectious diseases in the past, and here we show that parchment can also preserve animal pathogen DNA. Perhaps archives and libraries around the world contain genetic traces of outbreaks of animal diseases in the past.
At the same time, the researchers found no visible traces of damage on the pages with viral DNA. This does not necessarily mean that the animals were healthy: skin manifestations of sheep pox are often localized in areas of the body that are not covered with hair. In addition, during the manufacture of parchment, the skin surface was cleaned and treated, so the external signs of the disease could not be preserved.
The history of sheep pox dates back more than 3.7 thousand years.
To trace the history of the infection deeper, scientists studied not only manuscripts, but also sheep teeth from archaeological sites of the Bronze Age. Dental tissue is able to protect genetic material from destruction, so it is sometimes possible to detect traces of ancient infections after thousands of years.
Early samples of the virus date back to about 1875-1645 BC and 1336-1130 BC, respectively. Together with the data from the manuscripts, these findings show that the virus infected herds at least 3.7 thousand years ago.
By comparing ancient and modern genomes, the researchers also estimated the time of divergence of the main lines of the capriboxvirus family. These include sheep pox virus, goat pox virus, and the causative agent of nodular dermatitis in cattle. According to scientists, their evolutionary lines split between 11.5 thousand and 3.7 thousand years ago. This period coincides with the domestication of animals and the movement of herds from the Eurasian steppe to Europe. Such migrations could contribute to the spread of infections.
The ancient virus has hardly changed over the millennia
One of the most interesting results was that the sheep pox virus genome has changed relatively little over several millennia. A comparison of ancient sequences with modern ones showed that the pathogen maintained genetic stability for a long time. At the same time, medieval samples formed a separate evolutionary group, which differed from modern variants of the virus.
Kevin Daly, Head of Research
These genomes help us understand how pathogens evolved and how they affected past societies, such as the sheep pox virus, which, as we show, has been affecting flocks in Eurasia for at least three and a half millennia.
Sheep pox remains a dangerous disease for animal husbandry: The infection spreads rapidly among the herd, can lead to the death of animals and reduce the production of meat, milk and wool. According to the authors, studying ancient genomes will help to better understand the origin and evolution of modern pathogens. The researchers also suggest that similar traces of other infections may be found in historical documents and archives.
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