E-Insight

June 2005

CVMBS Researchers Trace Roots of Leprosy Across the Centuries

Colorado State University researchers, along with scientists from around the globe, have traced the origins of the ancient disease leprosy to East Africa. In a study released in Science magazine in May (see citation below), the experts present DNA evidence of where the disease began and how it spread across the globe thousands of years ago, debunking long-held beliefs about the migration of the disease directly from East Africa to West Africa.

The international group identified rare genetic variations among strains of the bacterium that cause the disease. Using DNA, the study presents new evidence that leprosy likely originated in East Africa and spread to Asia and Europe before being imported into West Africa by explorers. It was then transmitted to North America, South America and the Caribbean islands through slave trade and colonialism.

Scientists at the College’s Mycobacteria Research Laboratories who participated in the study include Dr. Patrick J. Brennan, principal investigator at the laboratory who has been researching tuberculosis and leprosy for more than 30 years, and Dr. John Spencer, a senior scientist with the laboratory. The origins study was led by Dr. Stewart T. Cole of the Institut Pasteur in Paris.

"The identification of these 'fingerprints' for the leprosy pathogen represents a very important new tool for medical experts," said Dr. Jeffrey Wilusz, head of the Department of Microbiology, Immunology and Pathology. "This information can be used to help scientists eventually eliminate this disease, which continues today to infect a significant number of people in countries around the globe."

The study's DNA information traces migration of the disease through simple mutations, called single nucleotide polymorphisms, or SNPs. Despite its status as an ancient disease, Mycobacterium leprae, the bacterium that causes leprosy, is known to have mutated these particular SNPs only four times. By studying populations across the globe and identifying which of the four established strains of the bacteria causes the disease in separate populations, the researchers were able to identify a timeline and geographical map of how the disease spread.

"We can track human migration patterns based on the dominant type of leprosy in specific regions," said Dr. Spencer. "This historical record of bacteria provides us with significant information about how the disease spread through migration, since leprosy only affects humans."

Colorado State's Mycobacteria Research Laboratories is at the global forefront in developing rapid diagnostic tests and skin tests for leprosy that can be used to diagnose the disease before individuals show symptoms. Leprosy remains a significant public health problem. The latest information from the World Health Organization shows that 620,672 new cases were diagnosed in 2002.

On the origin of leprosy. Science. 2005 May 13;308(5724):1040-2. Monot M, Honore N, Garnier T, Araoz R, Coppee JY, Lacroix C, Sow S, Spencer JS, Truman RW, Williams DL, Gelber R, Virmond M, Flageul B, Cho SN, Ji B, Paniz-Mondolfi A, Convit J, Young S, Fine PE, Rasolofo V, Brennan PJ, Cole ST.