Human not animals were source of Tuberculosis (TB): Study

The animals, as commonly believed, are not the original source of deadly bacteria of Tuberculosis, commonly known as TB, say scientists.

The study by an International team of scientists suggests that Tuberculosis (TB) did not originate in animals some 10,000 years ago, spreading to humans, as commonly believed. But the origin of tuberculosis has been traced back to African hunter-gatherers living 70,000 years ago, scientists claim.

Till today, Tuberculosis remains one of deadliest communicable diseases in humans that can kill 50 percent of individuals when left untreated, researchers said.

“Even today, TB causes 1-2 million deaths every year mainly in developing countries,” the scientists claimed.

Study

Using whole-genome sequencing of 259 Mycobacterium tuberculosis strains collected from different parts of the world, the researchers led by Sebastien Gagneux from the Swiss Tropical and Public Health Institute (Swiss TPH) determined the genetic pedigree of the deadly bugs.

The researchers compared the genetic evolutionary trees of mycobacteria and humans side-by-side. And surprisingly, the phylogenetic trees of humans and the TB bacteria showed a very close match.

This genome comparison indicates that TB mycobacteria originated at least 70,000 years ago in Africa.

“The evolutionary path of humans and the TB bacteria shows striking similarities,” said Gagneux.

Humans and TB bacteria not only have emerged in the same region of the world, but have also migrated out of Africa together and expanded across the globe, researchers said. The migratory behaviour of humans according to the adaptable situation has created favourable conditions for an increasingly deadly disease to evolve, the researchers suggested.

“We see that the diversity of tuberculosis bacteria has increased markedly when human populations expanded,” said Gagneux.

The results indicate further that TB is unlikely to have jumped from domesticated animals to humans, as seen for other infectious diseases.

The study was published in the journal Nature Genetics.