An African origin for Mycobacterium bovis

Area of Science:

• Veterinary Microbiology
• Evolutionary Biology
• Epidemiology

Background:

• Mycobacterium bovis and Mycobacterium caprae are key agents of tuberculosis in livestock and humans.
• Limited understanding of their global population structure, phylogeography, and evolutionary history exists.
• Whole-genome sequencing (WGS) of Mycobacterium tuberculosis complex (MTBC) has advanced understanding of human-adapted lineages.

Purpose of the Study:

• To elucidate the global population structure, phylogeography, and evolutionary history of M. bovis and M. caprae.
• To infer genetic relationships and geographic origins of M. bovis genotypes worldwide.
• To identify potential drivers of M. bovis dispersal.

Main Methods:

• Compiled a global collection of 3364 whole-genome sequences from M. bovis and M. caprae isolates.
• Sequences originated from 35 countries worldwide.
• Inferred phylogenetic relationships, geographic origins, and estimated ages of the pathogens.

Main Results:

• Resolved phylogenetic relationships among four previously defined and eight newly described M. bovis clonal complexes.
• Phylogeographic analysis suggests M. bovis originated in East Africa.
• Identified M. bovis groups that remained in Africa and others that dispersed globally, driven by cattle movements.

Conclusions:

• Provided a better understanding of the global population structure and evolutionary history of M. bovis.
• Findings can inform the development of molecular markers for epidemiological investigations.
• Facilitates targeted control strategies in settings where WGS is not feasible.