Origin and spread of Mycobacterium tuberculosis
The causative agents of tuberculosis, grouped in the Mycobacterium tuberculosis complex (MTBC), have infected one-third of the present human population and a wide range of other mammals. However, questions, such as why, where and when the disease began and expanded, have largely remained unanswered. A new study provides genetic evidence indicating that the common ancestor of the tuberculosis complex emerged some 40,000 years ago in East Africa, the region from where modern human populations disseminated around the same period. This initial step was followed 10,000 to 20,000 years later by the radiation of two major lineages, one of which spread from human to animals. In more recent years (approximately 180 years ago), coinciding with the human population explosion and the industrial revolution, the human-associated pathogen lineages have strongly expanded. These results thus reveal the strikingly parallel demographic evolution between humans and one of their primary pathogens.
Using mycobacterial tandem repeat sequences as genetic markers, the authors show that the MTBC consists of two independent clades, one composed exclusively of M. tuberculosis lineages from humans and the other composed of both animal and human isolates. The latter also likely derived from a human pathogenic lineage, supporting the hypothesis of an original human host. These findings unveil the dynamic dimension of the association between human host and pathogen populations.
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Tags: Biology, Emerging disease, Health, Medicine, Microbiology, Science, Tuberculosis
