Did Leprosy Originate in Europe?

A new study suggests the disease was far more diverse in Europe than previously believed

Skeletal remains showing evidence of leprosy from the Odense St. Jørgen cemetery in Denmark, which was established in 1270 and existed until 1560. Dorthe Dangvard Pedersen

Leprosy is one of the oldest and most notorious diseases of human history. Symptoms consistent with the leprosy are described in ancient records from India, China and Greece. Signs of the disease may even be present in a 4,000-year-old skeleton. But much about the affliction remains mysterious to modern-day researchers, who aren’t sure where leprosy came from or how it spread.

Various theories have identified India, Africa or the Middle East as possible origin points. But as Hannah Devlin reports for the Guardian, a new study has put forth compelling evidence to suggest that leprosy may have originated in Europe.

Also known as Hansen’s disease, leprosy is an infectious illness caused by the bacterium Mycobacterium leprae. It causes damage to the nerves, skin, eyes, nose and throat, and for centuries, people who contracted the illness were feared and stigmatized. The worldwide incidence of leprosy has declined in modern times, but the illness still occurs in many countries.

In Europe, leprosy was widespread between the 12th and 14th centuries, with the disease finally peaking in the 16th century. Previous research suggested that only two leprosy strains were present on the continent during this time, but the new study, published in PLOS Pathogens, has revealed that many more strains plagued medieval Europeans.

Researchers from the Max Planck Institute for the Science of Human History, EPFL Lausanne, the University of Zurich and several other institutions analyzed remains from 90 people that have deformations consistent with leprosy. The remains dated from 400 to 1400 A.D. and came from various locations in Europe, including Italy, Hungary, the Czech Republic and the UK, according to Gizmodo’s George Dvorsky.

From these remains, researchers were able to reconstruct 10 medieval M. leprae genomes—which surprised them.

“We found much more genetic diversity in ancient Europe than expected," Johannes Krause, senior author of the study and a director at the Max Planck Institute for the Science of Human History, explains in a statement. “Additionally, we found that all known strains of leprosy are present in Medieval Europe.”

Researchers were also surprised to discover multiple strains of the disease in the same burial sites. Three branches of M. leprae, for instance, were found within the Odense St. Jørgen cemetery in Denmark, highlighting the diversity of leprosy as it spread across Europe during the Middle Ages.

The new study doesn’t prove that leprosy originated in Europe, but it complicates previous ideas about the history of the disease. The diversity of leprosy strains uncovered by the new study suggests that the illness has existed in Europe for at least a few thousand years, and that it “may already have been widespread throughout Asia and Europe in antiquity,” Krause says in the statement. Leprosy may have even “originated in western Eurasia,” he adds.

Among the questions that still linger is how leprosy spread across Europe in centuries past. Researchers can’t be certain, but they did make an intriguing discovery while reconstructing the genome of an individual from Great Chesterford, England, whose remains date between 415 and 545 A.D. The individual represents one of the oldest known leprosy cases in the United Kingdom, and the M. leprae strain extracted from the skeleton is the same one that has been found in modern-day red squirrels.

This discovery supports previous research indicating that the critters may have played a role in transmitting leprosy among medieval Europeans. Last year, a study found a strain of leprosy, closely related to the one harbored by today’s squirrels, in remains from England, Denmark and Sweden. Viking traders of squirrel fur may have brought leprosy to England, the study’s authors consequently theorized.

Moving forward, the researchers behind the new study hope to locate skeletons even older than the one from Great Chesterford. By analyzing more genomes from leprosy patients of centuries past, scientists may be able to shed further light on the mysterious history of this devastating disease.

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