Monday, 24 June 2013

DNA Helps Get a Leg Up On Medieval Leprosy

Anyone who reads history books or historical fiction, or watches documentaries and movies with a historical theme, would have their own visuals of what leprosy is and what its place was in Medieval Western Europe. Sores and scabs. Parts of the body dropping off. Monks tending them in hospitals. Colonies of forlorn and wretched folk held together by bandages and propped up on crutches. Victims sent to islands where they would live out their days seperate from society. It is a brutal disease most commonly associated with Europe or the Middle East up until the late middle ages, even though there are still 200,000 cases of leprosy diagnosed worldwide every year.

From early Sixteenth century there was an abrupt decline in the disease throughout Western Europe. What was once a common disease that warranted dedicated hospitals and treatment facilities, became a rare disease with fewer and fewer cases presenting.

Nobody really knows why leprosy began to vanish in Western Europe, but of all the potential reasons being promoted amoung specialists it seems that the likely answer is that it was eliminated through a combination of a genetically developed resistance and natural selection.
In a recent study done by Ecole Polytechnique Fédérale de Lausanne in Switzerland, DNA was taken from the bones of five medieval leprosy cases who had died at various times between the Tenth Century and the Fourteenth Century.
Found in museum collections these skeletons had been originally buried in Sweden (Sigtuna), Denmark (Odense and Refshale) and England (Winchester). From this DNA they then tracked down Mycobacterium leprae- the bacterium responsible for leprosy. And, startlingly, it was discovered to closely resemble the modern leprosy pathogen.

A bacteria that can remain intact for centuries in its victims, M leprae was examined and found to have most likely survived due to its thick cell walls dense with fatty acids that can hold strong against attack and through which water does not easily penetrate. It was a tough little pathogen, but indicators in its pseudogenes show it was also not prone to evolving. So while Europeans evolved a gradual resistance, along with the practice of quarantining in the Middle Ages, Western Europe was able to move away from the disease and out breed it.

Evidence from other famous diseases will also be evaluated through the dna found in organic matter dating back hundreds of thousands of years. Through items like medieval teeth, bones, hair samples, faeces and plant material, microbiologists will be able to navigate traces of diseases such as tuberculosis, cholera, plague and even the Potato Blight and other plant diseases that could one day affect world wide supply of important starch rich foods.

The discoveries being made by these microbiologists are only the beginning of a fascinating journey to unlock disease in dna and learn from it. This knowledge can then be used to develop strategies to prevent strains of these diseases from devastating our populations and food sources again.

For more information:
The Research Report which was recently published in Science journal.
Genome Comparison in medieval and modern M. Leprae
An article on the report from the LA Times.
Leprosy, an Ancient Scourge, Largely Unchanged in the Modern Era

- MM

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