An international research team reconstructed entire genome sequences of the leprosy pathogen, Mycobacterium leprae, from five medieval skeletons unearthed in Denmark, Sweden, and the U.K. These skeletons date back to between the 10th and 14th centuries.
The researchers then compared their findings to 11 leprosy strains found in biopsy samples from modern-day patients suffering from the disease.
Surprisingly, the researchers found that the ancient leprosy DNA was well preserved - even more so than the human DNA of the skeletons, possibly due to the thick and waxy cell wall of the leprosy bacteria.
"Since the M. leprae DNA degrades slower than human - and probably other vertebrate -DNA, it should be possible to extract and sequence M. leprae DNA from environments and time periods in which we would not usually find DNA preserved, like the tropics or early, prehistoric time periods," study co-author Johannes Krause, professor of archaeological science at the University of Tübingen in Germany, said in a written statement. "So potentially we could study samples from the time of the disease's origin."
But for now, the researchers found that leprosy really hasn’t changed much genetically. Based on the study, only about 800 mutations have occurred among the 16 ancient and modern genomes analyzed.
Some of the medieval European strains are similar to modern-day strains in the U.S. - so for the Americas, leprosy origins may trace back to Europe. Leprosy was prevalent in Europe until the late Middle Ages, and now the disease infects about 200,000 people each year.