Ancient Skeletons Chronicle the Spread of Leprosy

When the young man known only as GC96 first arrived on British shores, it probably wasn't his strange accent that stuck out like a sore thumb, but rather, his scaly, putrefied skin and withered fingers and toes.

If, that is, GC96 was already showing symptoms of his leprosy. If not, the disease might have crept silently into England some 1,500 years ago.

That's a possibility raised by a study published today in PLOS One, which discovered DNA traces of Mycobacterium leprae, the bacteria that causes leprosy, on the skeletal remains of a 20-something-year-old man excavated from an Anglo Saxon burial in Essex, England. GC96, who probably hailed from southern Scandinavia, may have been Britain's patient zero for a disease that would plague the country for more than a thousand years to come.

What's more, the tools that led to these discoveries may help researchers visualize the spread of leprosy, and other ancient diseases, across continents and oceans.

"This is exciting both for archaeologists and for microbiologists," lead study author Sarah Inskip of Leiden University said in a statement. "It helps us understand the spread of disease in the past, and also the evolution of different strains of disease, which might help us fight them in the future."

Described in historical texts since ancient times, leprosy is a nasty disease that rots the skin, sometimes causing fingers and toes to shrivel and deform as cartilage is resorbed into the body. Leprosy was a pernicious epidemic in Europe by the late Middle Ages, but scientists still have much to learn about when, where, and how the disease originally spread throughout the continent.

The introduction of molecular tools into archaeology is shedding new light on that question. As researchers begin pairing DNA analyses, biomarkers and other chemical evidence, we're beginning to build a detailed picture of who the infected individuals were and what sorts of strains they carried, connecting the dots across space and time.

Case in point: The present study, in which archaeologists examined the remains of a young man buried in southeastern England during the 5th or 6th century. Patient GC96's skeleton showed changes consistent with leprosy, including a narrowing of the toe bones and withering of the joints. By extracting ancient DNA and lipid biomarkers from his bones, the researchers were able to confirm the diagnosis and conduct a detailed genetic study of the bacteria that caused the disease.

Molecular testing showed that this particular leprosy bug belonged to the 3I lineage, the same strain found later throughout continental Europe and, eventually, the Americas. Combining oxygen isotope values from the man's teeth, which loosely reflect the chemistry of the water he drank, and strontium isotopes in his tooth enamel, which can be linked to the geology of a person's homeland, the archaeologists concluded that the man probably came from outside Britain, perhaps from southwest Norway.

"Considering the early medieval population movements in north Western Europe at this time, this research potentially supports the notion of a Scandinavian origin for the 3I strain which emerged in Britain," the researchers write. "[This] adds considerable detail to the evolution of M. leprae and helps us begin to piece together the possible rise in prevalence of leprosy in the context of population movements in the Anglo-Saxon period."

There are a handful of cases worldwide that predate this young man, including several from second century BC Egypt, first century AD Israel, and 1st through 4th century AD Uzbekistan.

"We plan to carry out similar studies on skeletons from different locations to build up a more complete picture of the origins and early spread of this disease," Inskip said.

It's fascinating to think that through snippets of ancient DNA, and the atoms that tie people to the rocks and water of their country, the unwritten history of something as intangible as disease might be revealed.