Medieval skeletons give clues to leprosy origins
As part of their study, scientists extracted DNA from skeletons that were 1,000 years old
The genetic code of leprosy-causing bacteria from 1,000-year-old skeletons has been laid bare.
Similarities between these old strains of the bug and those prevalent today have given scientists unique insights into the spread of the disease.
It has revealed, for example, the key role played by the medieval Crusades in moving the pathogen across the globe.
The researchers tell Science magazine they hope their study will lead them to the ancient origins of the leprosy.
In medieval times, a sufferer of leprosy was likely to be an outcast, secluded from society in quarantined colonies. Then as now, there was a social stigma with having the disease, but it can be cured if caught early. If left untreated, it can leave sufferers deformed and crippled.
The scientists in this new study compared the genetics of the disease-causing bacteriumMycobacterium leprae found in five medieval skeletons from Europe with 11 modern strains.
The DNA comparison showed that one type of leprosy found in Europe 1,000 years ago is the same as one present in the Middle East now.
This strengthened the view that the disease spread during the Crusades, said Johannes Krause, from the University of Tübingen, Germany, one of the authors of the work. This was a period when Christian armies fought for control of what they called the Holy Land.
It remains unclear which direction the disease spread, but "lines of evidence suggest an Asian origin of the disease", as the earliest evidence of leprosy comes from a 4,000-year old skeleton found in India.
"This skeleton can only tell us it was present in Asia around 4,000 years ago, but we do not know where the origin of the disease is," Prof Krause told BBC News.
Another of the medieval strains is similar to one found in the Americas today. This suggests the disease was not something the first American settlers carried with them when they originally migrated from Asia, but is a more recent development that was probably introduced when Europeans colonised the continent, added Prof Krause.
"One really surprising finding was that the DNA was so well preserved, better than any ancient DNA I have ever studied," he said.
"This opens up the possibility to study the evolution of the disease in much older remains, to understand how it evolved and adapted to
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