One of the deadliest infectious human disease tuberculosis(TB) , origin have been tracked back to hunter-gatherer groups in Africa 70,000 years ago, says an international team of scientists.
The study goes in contradiction of common beliefs that’s Tb originated in animals only 10,000 years ago and spread to humans. TB causes more than 1-2 million deaths every year mainly in developing countries, even today. The origin of the disease in space and time has now identified by Sebastien Gagneux from the Swiss Tropical and Public Health Institute (Swiss TPH).
They defined the genetic lineage of the deadly buds, by using whole –genome sequencing of 259 Mycobacterium tuberculosis strains. The work, published in Nature Genetics, summaries that TB mycobacteria originated in Africa at least 70.000 years ago.
The evolutionary path of human and TB bacteria shows stunning close relationship, says Sebastien Gagneux. They compared the genetic evolutionary tree of mycobacteria and humans, the phylogenetic trees of human and the TB showed close similarities. This close bounding between the two lasting tens of thousands of years. TB migrated out of Africa and expanded all over the world during the Neolithic Demographic Transition (NDT).
“We see that the range of tuberculosis bacteria has increased strikingly when human populations expanded. After a certain time Tb is able to reactivate itself. “Says biologist Sebastien Gagneux.
Another feature of Tb is that people can suffer with it for several years without showing any symptoms. It remains a global threat, triggering 1.4 million deaths in 2011, according to WHO
“If there are few infected people, it, makes no harm to kill them, as you would risk killing itself too. TB’s drive increased virulence after the increased human population and NDT.”
“Next step to defeat this global threat in this research would be to use genetic information to understand the mechanism of TB, said Dr Inaka Comas, lead author to the research.
In many countries, multidrug resistance against first treatments is a rising risk. For that reason, the study of the evolutionary patterns of TB bacteria may help future patterns of the disease.
Thousands of TB genomes are now being sequenced in big databases so that in the next 5 years we’ll know more about the development and movement of TB.