The Journal of Young Investigators: An Undergraduate, Peer-Reviewed Science Journal

09 February 2005 - The ravages of tuberculosis (TB) in Medieval Europe may have eliminated leprosy, according to a University College London (UCL) study published in the latest issue of Royal Society Proceedings B. The once-feared effects of leprosy have mostly given way to TB, which has infected a third of the world’s population.

“Records from the 19th and early 20th century confirm our suggestion that patients infected with both leprosy and tuberculosis will die of the tuberculosis,” says co-lead author Helen Donoghue from the UCL’s Centre for Infectious Diseases and International Health. “It [TB] spreads more quickly and will kill you more quickly, especially if your natural immunity is low—as it would be if you had a chronic progressive disease like leprosy.”

Archaeologists and paleopathologists have long known that leprosy declined in Europe as tuberculosis appeared to increase. Scientists previously speculated that the biologically similar diseases may have conferred cross-immunity, meaning that TB survivors could have been immune to leprosy.

But Donoghue and her colleagues think that their findings point toward TB as a quick killer, rather than protector from leprosy. Examining bone material from human remains at sites in Israel, Egypt and Europe, they found DNA traces of both TB and leprosy infection in 42 percent of the samples.

“I believe it is the first time anyone has checked for coinfection looking at archaeological material,” said Donoghue. She explained that co-infection of TB and leprosy has often been overlooked by researchers

The next step for the team would be to find better-preserved DNA of the diseases in more archaeological samples.

“We hope to look for molecular fingerprints of the TB and leprosy bacteria and to compare these with the strains that are present in the world today,” Donoghue says.

“By understanding what happened in the past, we hope to be in a better position to understand the relationship between these bacteria and ourselves, and the factors that are important in susceptibility and resistance.”

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