Written on Skin: sheeppox DNA in medieval gospel books

Sample chapter (draft)

Chapter 1. Written on Skin: The Virus in the York Gospels

A book that is still in use

In York Minster, the great cathedral in the north of England, there is a book that has been part of the life of the church for about a thousand years. It is called the York Gospels. It contains the four gospels of the New Testament. Over the centuries, other things were added to it: a letter from King Cnut, who ruled England from 1016 to 1035, documents about who owned which land, and the oaths sworn by the cathedral's deans, archdeacons, canons and vicars choral between the fourteenth and sixteenth centuries [3]. Scholars think it was written around the year 1000 in the scriptorium of St Augustine's monastery in Canterbury and brought to York by Archbishop Wulfstan around 1020 [3]. It is one of only a small number of English gospel books from before the Norman Conquest of 1066 that survived the Reformation, and researchers writing in 2017 noted that it was still used in church ceremonies [3].

Think about what that means. For a thousand years, people have opened this book, turned its pages, rested their hands on it and made solemn promises over it. All of that handling has left traces, and some of those traces are biological.

This chapter is about one trace nobody expected to find. In 2026, a team of more than thirty institutions, led by University College Dublin, reported DNA from sheeppox virus on pages of the York Gospels [1, 2]. Sheeppox still kills sheep and wrecks farmers' incomes in many parts of the world today [5]. To see how a medieval gospel book ended up holding a record of a farm disease, we first need to know what the book is made of.

Every page was once an animal

Before paper was common in Europe, important books were written on parchment, which is animal skin that has been specially prepared. Skins were soaked in a bath of water and lime, and the flesh was scraped away [1]. The skin was then stretched and dried into a thin, strong sheet that could last for many centuries. A single large sheet folded in half gave two leaves of a book, which specialists call a bifolium.

So a parchment book is, among other things, a collection of animals. Each page came from a calf, a sheep or a goat that lived and died on a real farm. That makes old manuscripts what scientists call a bio-archive. As the UCD team put it, parchment preserves "the health of the animal at the time of its death centuries ago" [2].

For a long time nobody could read that biological record without damaging priceless books. That changed with a simple tool: an ordinary rubber eraser. When a conservator gently rubs a page, the eraser picks up tiny amounts of protein and DNA from the surface, and the crumbs it leaves behind can be collected and tested. In 2017, scientists at the University of York, Trinity College Dublin and partner institutions used this method on the York Gospels [3, 4].

What the 2017 study found

That first study was a kind of biological biography of the book. Its main findings are worth knowing, because they set up the 2026 discovery.

It was mostly made from calves. Testing the proteins in eraser crumbs from every bifolium showed that the original gospels were made from calfskin, apart from a single bifolium of sheepskin. The later additions from the fourteenth century were made entirely of sheepskin [3]. A few pages could not be tested, because conservation work in the 1950s had covered them in silk gauze [3].

People left their mark. On average, about 11% of the DNA recovered from the pages was human, roughly twice the level in the control samples. It was highest on pages that people handled most [3]. One of those was folio 6, which contains oaths, at 17.5% [3]. The researchers linked this to the book's long use in ceremonies.

The bacteria were like those on human skin. The microbes living on the pages looked like the ones found on human skin, probably passed on by all those hands. One group of bacteria, Saccharopolyspora, turned up on every page sampled, and other studies have linked it to parchment decay [4].

The makers may have preferred female calves. The York team reported a possible bias towards skins from female calves, which might reflect how people valued different animals at the time [4]. With only a small number of pages tested, this is best treated as an interesting hint, not a firm conclusion.

Taken together, these findings showed that a manuscript can be read in two ways. You can read the words on the page, or you can read the biology of the page itself.

The 2026 discovery

Nine years later, a much bigger study took the idea further. Louis L'Hôte, Kevin G. Daly and colleagues screened 754 samples of animal remains and historical materials from across Eurasia, spanning more than 14,000 years, for viruses in the capripoxvirus group [1]. This is the group that includes sheeppox, goatpox and lumpy skin disease. Most of the 754 samples came from earlier studies. Only a small share were newly reported material [1].

Sheeppox virus turned up in 39 specimens [1]. From those, the team built 22 viral genomes, 21 of them reported for the first time. Some cover nearly the whole virus and others only part of it [1]. The oldest came from sheep teeth at two Bronze Age settlements on the Eurasian steppe. One was at Myrzhik in Kazakhstan, from a sheep dated to between 1875 and 1645 BCE. The other was at Rublevo-VI in the Altai region of Russia, dated to between 1336 and 1130 BCE [1]. Those teeth are the reason the study can say sheeppox has threatened the food security of Eurasian communities for more than 3,700 years [1].

A large share of the finds, though, came from books. The team detected sheeppox DNA in 17 parchment samples and one paper sample from medieval manuscripts made in Britain, the Upper Rhine region, Austria and France. The parchment dates from the early eighth century to the fourteenth century [1].

Three of the positive pages came from the York Gospels. Two were from the original book, made around 990 to 1020, and one was from a later medieval document that had been added to it [1].

The York Gospels were not the only famous book on the list. Others included:

• The Corpus Glossary, held at Corpus Christi College, Cambridge. It was made around 800, probably in Canterbury, and lists Latin words with Latin or Old English meanings. It is one of the earliest English dictionaries [1, 2].
• An annotated copy of the Epistles of St Paul, held at Trinity College, Cambridge, and copied around 700 in either Ireland or Northumbria [1].
• Four pages from a fifteenth-century volume of the Speculum Historiale, a medieval encyclopedia of history. This particular volume became famous because it was once bound with the Vinland Map, which later analysis showed to be a modern forgery [1].

The book was not just storing pictures of old life. It was storing traces of an old disease.

The puzzle: these were not all sheep

Here the story takes a turn that most headlines missed. You might expect sheeppox DNA to come only from pages made of sheepskin. It did not.

Of the 17 positive parchment pages, the team found that 10 were calfskin, 4 were goatskin and only 3 were sheepskin [1]. The two positive pages from the original York Gospels were both calfskin. The only positive York Gospels page made from sheepskin was the later document added to the book [1]. (This matches the 2017 finding that the original gospels are almost all calf and the later additions are sheep [3].)

So it would be wrong to say the York Gospels were "made from infected sheep." The truth is stranger and more interesting. How did a sheep virus end up on the skin of a calf?

The researchers set out several possible answers and do not claim to know which is right [1]:

1. The calves were really infected. Sheeppox has been reported in a small number of goat outbreaks, but the authors say they know of no natural cases in cattle [1]. Parchment calves were also usually very young, around 6 to 8 weeks old. If their mothers had been exposed to the virus, the calves should have been protected by antibodies in their mothers' first milk [1]. Still, one calfskin page, from the Epistles of St Paul, had no sign of sheep DNA. The researchers say that makes contamination from a sheep source less likely for that page, and that a slightly higher amount of virus DNA on the flesh side of the skin may support real infection. That difference was not statistically significant, so it remains a hint [1].

1. The skins were contaminated while the parchment was being made. Skins were soaked together in lime pits. Sheeppox virus can survive outside the body for months, especially in scabs that fall off sick animals [1, 5]. A calfskin soaking in the same pit as a skin from an infected sheep could have picked up viral DNA.

1. Neighbouring pages rubbed off on each other. In a book where pages from infected sheep sit next to pages from healthy calves, traces could pass from one to the other [1].

1. Sheep products were used in making or repairing the page. Six of the eight parchments that showed DNA from more than one animal had sheep as the second most common signal [1]. The one positive paper document may be explained the same way. Paper at the time was often coated with gelatin, a glue made from animal skin, leather scraps or parchment offcuts [1].

For the reader, the useful lesson is how carefully the scientists handled this. They reported an unexpected result, listed the possible explanations, and said plainly which ones their data could and could not rule out. That is a good habit for anyone talking about animal health, whether in a lab, at a market or on a short video.

Pages without scars

You might also wonder whether the infected pages look diseased. They do not. The team reports that the positive pages show no visible lesions [1]. That may not be surprising. Sheeppox sores are often limited to the parts of the body without wool, and parchment makers scraped the skins heavily [1]. Some skinners may have avoided the damaged areas, or scribes may have thrown out marked skins. On the other hand, a separate study of sheep that died of sheeppox in France between the seventeenth and nineteenth centuries found that some of those animals had been skinned anyway [1, 12]. Being infected did not always stop people using the hide.

The researchers mention only one possible exception: signs of pox-like marks on the parchment of the Codex Amiatinus, an eighth-century bible made from goat and sheep skins [1]. They call these "indications," and we should too.

What the York Gospels virus tells us about its family tree

One of the York Gospels pages, a calfskin leaf the team labels YG16, gave enough DNA to rebuild about ten times coverage of the virus's genome [1]. That was enough to place it on the sheeppox family tree. The medieval genomes from the manuscripts group together in or near a branch that sits beside modern sheeppox. The authors describe this branch as presumably extinct [1]. In other words, the sheeppox that circulated in medieval Europe seems to belong to a lineage that is no longer around. The modern strains descend from a related branch.

The study found something else that matters for later chapters. The sheeppox genome has been very stable for thousands of years. A set of genes that are switched off in modern sheeppox were already switched off in the oldest Bronze Age genome [1]. As lead author Louis L'Hôte put it, "unlike the smallpox virus, the sheeppox virus genome was very stable over the last few millennia" [2]. The team suggests that the virus's key adaptations to sheep probably happened before about 4,000 years ago [1]. Chapter 6 looks at what that might, and might not, mean for the future.

From a cathedral to a cattle market

Why should a farmer in Kenya, Pakistan, Greece, Mongolia or Wales care about a gospel book in York?

First, because it shows how ordinary this disease once was in Europe. The authors conclude that the large number of medieval sheeppox genomes suggests infection of sheep "was a frequent challenge to European societies of this time" [1]. The people who made these books lived alongside the disease, much as many farmers around the world do today.

Second, because the clues in the parchment point to the same weak spots that farmers face now. The virus survives for months in scabs and wool [5]. It spreads through close contact and through contaminated objects, such as equipment, vehicle wheels and boots [5]. The FAO field manual on sheeppox and goatpox says that in most cases the virus reaches a farm through newly purchased animals [5]. Britain shows how this happens. According to records cited by the researchers, sheeppox was treated as a new and foreign disease when it was brought back into the country with infected sheep in 1847, after centuries without it [1]. The UK government says the disease has not been present in Great Britain since the 1800s [13].

Third, because the disease is still here. Sheeppox and goatpox are widespread across Africa (except southern Africa), the Near East and Asia, with outbreaks reported in Spain, Bulgaria, Greece and Romania in recent years [5]. In Greece, according to the Greek veterinary authorities' report to a WOAH Europe expert meeting, there were 2,194 outbreaks and 492,882 sheep and goats culled between August 2024 and late June 2026 [10]. In northeast Nigeria, a study of small farmers hit by sheeppox, goatpox and lumpy skin disease found that sick sheep and goats sold for well over half less than healthy ones. Most farmers had not been able to replace the animals they lost, mainly because they lacked money or feared the disease would come back [9]. The farmers in that study most often bought replacement animals at livestock markets, the same places where sick animals were sold. That makes markets likely hubs for spreading the disease [9].

The York Gospels cannot tell us how to vaccinate a flock. What they can show, with unusual force, is that this disease has followed farmers for thousands of years, and that it travels with animals, skins and the people who move them. The rest of this book follows that trail, from the steppe to the scriptorium to today's farms, and ends with steps any farmer can take, even on a tight budget.

On your farm: three ideas to carry forward

These are covered in detail in Chapters 9 and 10. They are based on FAO and WOAH guidance and are not a substitute for advice from your own vet or veterinary service.

• Treat every new animal as a possible carrier. FAO advises that when the disease is circulating nearby, farmers should avoid bringing in new animals. If they must, they should buy only from trusted sources, check the animals for signs of disease, and keep them apart from the herd for 21 days. Ideally, new animals should be vaccinated 21 days before they arrive [5]. In Ireland, the agriculture department suggests keeping newly bought animals apart for at least four weeks [14].
• Watch the shared places. Markets, communal grazing, watering points and overnight pens bring animals into close contact [5, 9]. Where you can, keep your animals apart from other herds at water and on grazing. FAO notes that in some villages this is not practical and that animal welfare, including access to feed, must come first [5].
• Report early. Sheeppox and goatpox are notifiable diseases under WOAH [1, 5]. In the UK, the law requires anyone who suspects them to report it immediately [13]. Neither sheeppox nor goatpox infects people [5, 6].

References for this chapter

1. [1] L'Hôte L., Sacristán L., Ferguson R., ... Story J., Collins M., Teasdale M.D., Binois-Roman A., Calvignac-Spencer S., Daly K.G. (2026). Three thousand five hundred years of sheeppox virus evolution inferred from archaeological and codicological genomes. Science Advances 12(36), eaeh3571. https://doi.org/10.1126/sciadv.aeh3571 (Open access, CC BY 4.0. Preprint: bioRxiv 10.64898/2026.02.23.707469.)
2. [2] University College Dublin (2 September 2026). Hidden DNA in medieval gospels reveal history of deadly livestock virus. News release, EurekAlert! https://www.eurekalert.org/news-releases/1142448
3. [3] Teasdale M.D., Fiddyment S., Vnouček J., Mattiangeli V., Speller C., Binois A., Carver M., Dand C., Newfield T.P., Webb C.C., Bradley D.G., Collins M.J. (2017). The York Gospels: a 1000-year biological palimpsest. Royal Society Open Science 4, 170988. https://doi.org/10.1098/rsos.170988
4. [4] University of York (2017). Revealing the hidden biographies of the York Gospel. News release. https://www.york.ac.uk/news-and-events/news/2017/research/revealing-york-gospel/
5. [5] Tuppurainen E. & Beltrán-Alcrudo D. (2026). Sheep pox and goat pox – A field manual for veterinarians. FAO Animal Production and Health Manual No. 33. Rome: FAO. https://doi.org/10.4060/cd7794en
6. [6] World Organisation for Animal Health (WOAH). Sheep pox and goat pox (disease page). https://www.woah.org/en/disease/sheep-pox-and-goat-pox/
7. [7] World Organisation for Animal Health (WOAH). Lumpy skin disease (disease page, last updated 9 July 2026). https://www.woah.org/en/disease/lumpy-skin-disease/
8. [8] WOAH. Terrestrial Animal Health Code, Chapter 14.9: Infection with sheep pox and goat pox. https://www.woah.org/fileadmin/Home/eng/Health_standards/tahc/2024/en_chapitre_sheep_pox_goat_pox.htm
9. [9] Limon G., Gamawa A.A., Ahmed A.I., Lyons N.A., Beard P.M. (2020). Epidemiological characteristics and economic impact of lumpy skin disease, sheeppox and goatpox among subsistence farmers in Northeast Nigeria. Frontiers in Veterinary Science 7, 8. https://doi.org/10.3389/fvets.2020.00008
10. [10] Hellenic Republic veterinary authorities (29 June 2026). Overview of the SGP epidemiological situation in Greece. Presentation to the 2nd Standing Group of Experts (SGE) on PPR and SGP in Europe, WOAH Regional Representation for Europe. https://rr-europe.woah.org/app/uploads/2026/08/SGE_SGP_GREECE.pdf
11. [11] EFSA (2026). Sheep and goat pox: vaccines and vaccination scenarios to control the epidemics in Greece and Bulgaria in 2025. EFSA Journal 24, e9928. https://doi.org/10.2903/j.efsa.2026.9928
12. [12] Binois-Roman A., L'Hôte L., Ferguson R., Daly K.G. (2026). Evidence of sheeppox in seventeenth- to nineteenth-century France: a multi-disciplinary investigation of a sheep mass mortality assemblage. Royal Society Open Science 13, 252320. https://doi.org/10.1098/rsos.252320
13. [13] Defra & APHA (updated 28 September 2023). Sheep pox and goat pox: how to spot and report these diseases. GOV.UK. https://www.gov.uk/guidance/sheep-and-goat-pox
14. [14] Department of Agriculture, Food and the Marine, Ireland. Sheep Pox and Goat Pox. https://www.gov.ie/en/department-of-agriculture-food-and-the-marine/publications/sheep-pox-and-goat-pox/