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Curr Biol. 2015 Dec 21;25(24):3260-6. doi: 10.1016/j.cub.2015.10.061. Epub 2015 Dec 10.

Population Genomics of Mycobacterium tuberculosis in Ethiopia Contradicts the Virgin Soil Hypothesis for Human Tuberculosis in Sub-Saharan Africa.

Author information

1
Genomics and Health Unit, FISABIO Public Health, Valencia 46020, Spain; CIBER (Centros de Investigación Biomédica en Red) in Epidemiology and Public Health, Instituto de Salud Carlos III, Madrid 28029, Spain. Electronic address: inaki.comas@uv.es.
2
Armauer Hansen Research Institute, PO Box 1005, Addis Ababa, Ethiopia.
3
Armauer Hansen Research Institute, PO Box 1005, Addis Ababa, Ethiopia; Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel 4002, and University of Basel, Basel 4003, Switzerland.
4
Aklilu Lemma Institute of Pathobiology, Addis Ababa University, PO Box 1176, Addis Ababa, Ethiopia.
5
Bovine TB Research Group, Animal and Plant Health Agency, Surrey KT15 3NB, UK.
6
Center for Molecular Bacteriology and Infection, Department of Medicine, Flowers Building, South Kensington, Imperial College London, London SW7 2AZ, UK.
7
Genomics and Health Unit, FISABIO Public Health, Valencia 46020, Spain.
8
Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel 4002, and University of Basel, Basel 4003, Switzerland.
9
The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London NW7 1AA, UK.
10
Bovine TB Research Group, Animal and Plant Health Agency, Surrey KT15 3NB, UK. Electronic address: stefan.berg@apha.gsi.gov.uk.

Abstract

Colonial medical reports claimed that tuberculosis (TB) was largely unknown in Africa prior to European contact, providing a "virgin soil" for spread of TB in highly susceptible populations previously unexposed to the disease [1, 2]. This is in direct contrast to recent phylogenetic models which support an African origin for TB [3-6]. To address this apparent contradiction, we performed a broad genomic sampling of Mycobacterium tuberculosis in Ethiopia. All members of the M. tuberculosis complex (MTBC) arose from clonal expansion of a single common ancestor [7] with a proposed origin in East Africa [3, 4, 8]. Consistent with this proposal, MTBC lineage 7 is almost exclusively found in that region [9-11]. Although a detailed medical history of Ethiopia supports the view that TB was rare until the 20(th) century [12], over the last century Ethiopia has become a high-burden TB country [13]. Our results provide further support for an African origin for TB, with some genotypes already present on the continent well before European contact. Phylogenetic analyses reveal a pattern of serial introductions of multiple genotypes into Ethiopia in association with human migration and trade. In place of a "virgin soil" fostering the spread of TB in a previously naive population, we propose that increased TB mortality in Africa was driven by the introduction of European strains of M. tuberculosis alongside expansion of selected indigenous strains having biological characteristics that carry a fitness benefit in the urbanized settings of post-colonial Africa.

PMID:
26687624
PMCID:
PMC4691238
DOI:
10.1016/j.cub.2015.10.061
[Indexed for MEDLINE]
Free PMC Article

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