Leprosy originated in Africa or Near East - study

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Leprosy, a disease widely believed to have been spread out of India, in fact appears to have originated in Africa or the Near East, scientists said on Thursday.

“The disease seems to have originated in Eastern Africa or the Near East and spread with successive human migrations,” researchers reported in Friday’s issue of the journal Science.

This is not what historians had believed.

”Leprosy is believed to have originated in the Indian subcontinent and to have been introduced into Europe by Greek soldiers returning from the Indian campaign of Alexander the Great. From Greece, the disease is thought to have spread around the Mediterranean basin, with the Romans introducing leprosy into the Western part of Europe,” the researchers wrote.

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Leprosy is an infectious disease that has been known since biblical times. It is characterized by disfiguring skin lesions, peripheral nerve damage, and progressive debilitation.

Causes, incidence, and risk factors

Leprosy is caused by the organism Mycobacteriumleprae. It is a difficult disease to transmit and has a long incubation period, which makes it difficult to determine where or when the disease was contracted. Children are more susceptible than adults to contracting the disease.

Leprosy has two common forms, tuberculoid and lepromatous, and these have been further subdivided. Both forms produce lesions on the skin, but the lepromatous form is most severe, producing large disfiguring nodules.

All forms of the disease eventually cause peripheral neurological damage (nerve damage in the extremities) manifested by sensory loss in the skin and muscle weakness. People with long-term leprosy may lose the use of their hands or feet due to repeated injury resulting from lack of sensation.

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In fact, the new study suggests that until Europeans explored and conquered much of the world, the disease that carries perhaps more stigma than any other was fairly contained, they said.

A careful genetic analysis of the bacteria that causes the disease, which attacks the nerves and skin, suggests that colonial-era explorers and slave traders spread leprosy across the rest of Africa and into the Americas in relatively recent times.

“Europeans or North Africans introduced leprosy into West Africa and the Americas within the past 500 years,” the researchers wrote.

ARMADILLOS HELP STUDY

It has been difficult to study Mycobacterium leprae because the bacillus does not grow well in lab dishes. It grows and spreads slowly in humans, too, and significant studies were only possible after it was found that armadillos are easily infected and can be used to grow large amounts of the bacteria.

The researchers, including teams in France, the United States, Brazil, Venezuela and Madagascar, compared the genetic codes of seven strains of Mycobacterium leprae taken from patients around the world.

They found very few genetic differences - a surprising finding in such an old and widespread organism.

But tracing these rare variations in the genetic code called single nucleotide polymorphisms or SNPs helped link bacteria found in one part of the world to bacteria common in another part.

“The strain of M. leprae responsible for disease in most of the Americas is closest to the European/North African variety,” they wrote.

Now more commonly known as Hansen’s disease, leprosy, whose existence can be traced in ancient texts as far back as about 600 BC in Egypt, no longer condemns patients to live in colonies.

More than 760,000 new cases were diagnosed in 2002, according to the World Health Organization, and Brazil, Madagascar, Mozambique, Tanzania, and Nepal had 90 percent of all cases.

Leprosy causes skin lesions and thickening, and patients can lose extremities because of nerve damage. Fingers and toes can become numb as the bacteria attack the nerves.

As with another bacillus - Tuberculosis - Hansen’s disease must be treated with antibiotics for months to be eradicated. 

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