Study reveals how leprosy disappeared from Europe

How did leprosy disappear from Europe?  Have you asked that question before?  It's much like a question I asked a friend when I first visited the United States.  I remember jokingly asking the friend during an outdoor evening meeting  - What did you do to your mosquitoes?  I discovered I'm not the only one who's asked that question. There are still mosquitoes in parts of the US.  Yes, there are. That I later found out.  Although we are making good progress in depopulating them in Africa, they still exist in my village.  Sometimes they are helpful in reminding us when to wake up should we oversleep.
Leprosy used to be very widespread in Europe.  Today the disease is rarely heard about there.  It's now more of a phenomenon for the developing world.  How did this happen? Rawstory.com reports of a new study in Europe that gives us a clue:

Patient at Masanga Leprosy Hospital in Sierra Leone

"Ancient DNA isolated from the mass grave of a 15th century leper colony has given scientists a clue as to why the one-time scourge of humanity has all but vanished from western Europe.

 The scientists believe that a certain gene that makes people highly resistant to leprosy spread through the population of Europe, gradually conveying a kind of mass immunity

According to NPR’s Shots Health News blog, a paper published Thursday in Science magazine explained that human beings themselves changed to overcome the once-prevalent skin disease.
Leprosy, also known as Hansen’s disease, afflicted as many as 1 in 30 citizens of Western Europe at its height in the 15th century. In Medieval woodcuts and drawings, lepers are represented almost as frequently as Christ and the Virgin Mary. But then, in the era after the Crusades, the disease mysteriously all but vanished from the continent.
Scientists wondered whether the bacteria that causes leprosy, Mycobacteriam leprae, had mutated into some less virulent form, or whether Europeans developed immunity. According to the study published in Science, it wasn’t the bacteria that mutated, it was the people.
Stewart Cole of the Ecole Polytechnique Fédérale de Lausanne, one of the study’s lead authors, told NPR that his team extracted DNA from the mass grave of a Medieval leper colony. DNA of any kind of is extremely difficult to extract from bones, but the team met with success when they were able to remove a small amount of tissue from a 600-year-old rotted tooth.
The material they found was “a mixture of human DNA, microorganisms and contaminating DNA from other bones and surrounding soil,” said Cole, but they were able to fully reconstruct a 600-year-old strain of leprosy and map its genome, only to find that it is essentially identical to living leprosy infecting people in the developing world today.  Cole told NPR, “If the explanation of the drop in leprosy cases isn’t in the pathogen, then it must be in the host, that is, in us.”The scientists believe that a certain gene that makes people highly resistant to leprosy spread through the population of Europe, gradually conveying a kind of mass immunity.Today, leprosy infections are treated with antibiotics and can be handled quickly and effectively if caught early. Stigma associated with the disease often keeps people in the developing world from seeking help for the malady until it has run amok in the system, causing irreversible damage."