A new study based on skeletal remains suggests that leprosy began to spread from Europe to other parts of the world. Interestingly, the study also finds that the disease may have jumped over the species barrier from humans to squirrels.
Hansen's Disease: Leprosy
Leprosy is a contagious disease that affects the nerves, skin, eyes, and mucous membranes. It was once feared as a highly contagious and dreaded disease for millennia. Fortunately, however, it can be treated and cured.
The words "Hansen" was named after Norwegian physician Gerhard Armauer Hansen, who is remembered for his identification of the bacterium Mycobacterium leprae in the late 1800s. The bacterium is known to be the primary cause of the disease.
It is not known how precisely leprosy is transmitted between people. According to the Centers for Disease Control and Prevention, the disease is rare in the United States, but as many as 2 million people worldwide are permanently disabled as a result of it, with around 200,000 being infected every year. It is mostly widespread in African and Asian countries, including Democratic Republic of Congo, Mozambique, India, and Bangladesh.
Previous studies suggested that leprosy originated either in Eastern Africa or the Near East and was transmitted to other parts of the world through successive human migrations. Others believe that it began to spread from India with skeletal evidence of the disease dating to 2000 B.C.
New Study Based On Skeletal Remains
In the new study published on May 10 in the journal PLOS Pathogens, scientists analyzed the remains of 90 individuals that date back to around 400 A.D. and 1400 A.D. in Europe. These individuals were thought to have been infected by leprosy because of the malformations of their skeletons.
Based on this analysis, researchers discovered that there was a much higher diversity of leprosy strains in medieval Europe than previously thought. This led the scientists to speculate that the disease may have begun to spread from Europe.
"Additionally, we found that all known strains of leprosy are present in Medieval Europe, suggesting that leprosy may already have been widespread throughout Asia and Europe in antiquity or that it might have originated western Eurasia." said Johannes Krause, director of the Max Planck Institute for the Science of Human History and senior author of the study.
Oldest Strain From Ancient England
In addition, the scientists also managed to reconstruct one Mycobacterium leprae genome, which they found dates back to around 415 A.D. and 545 A.D. This genome is the oldest and comes from Great Chesterford in England.
Jumping The Species Barrier
Surprisingly, the scientists also discovered that the oldest strain is the same one found in modern-day red squirrels. This led them to believe that both humans and squirrels may have played a role in the transmission of leprosy in Europe.
The study, which is the largest to date, involved scientists from the Max Planck Institute for the Science of Human History, the University of Tübingen, EPFL Lausanne, and the University of Zurich. As of now, the scientists plan to analyze older skeletal remains in an effort to verify recorded cases of leprosy that date back to thousands of years.