Abstract
Mycobacterium bovis is the pathogenic agent responsible for bovine tuberculosis (bTB), a zoonotic disease affecting mostly cattle, but also transmittable to humans and wildlife. Genetic studies on M. bovis allow to detect possible routes of bTB transmission and the identification of genetic reservoirs that may provide an essential framework for public health action.We used a database with 1235 M. bovis genotypes collected from different regions in Africa with 45 new Mozambican samples. Our analyses, based on phylogeographic and population genetics’ approaches, allowed to identify two clear trends. First, the genetic diversity of M. bovis is geographically clustered across the continent, with the only incidences of long-distance sharing of genotypes, between South Africa and Algeria, likely due to recent European introductions. Second, there is a broad gradient of diversity from Northern to Southern Africa with a diversity focus on the proximity to the Near East, where M. bovis likely emerged with animal domestication in the last 10,000 years.Diversity indices are higher in Eastern Africa, followed successively by Northern, Central, Southern and Western Africa, roughly correlating with the regional archaeological records of introduction of animal domesticates. Given this scenario M. bovis in Africa was probably established millennia ago following a concomitant spread with cattle, sheep and goat. Such scenario could translate into long-term locally adapted lineages across Africa.This work describes a novel scenario for the spread of M. bovis in Africa using the available genetic data, opening the field to further studies using higher resolution genomic data.
Highlights
Mycobacterium bovis is the major causal agent of bovine tuberculosis in cattle, the world’s most neglected zoonotic disease that needs urgent attention, especially in developing countries [1, 2]
We describe the genetic diversity distribution in Africa of the pathogen Mycobacterium bovis, the responsible for bovine tuberculosis, mostly present in cattle and transmittable to other animals including humans
This diversity is geographically clustered within the African continent meaning that the genetic diversity was established through independent evolution within different areas
Summary
Mycobacterium bovis is the major causal agent of bovine tuberculosis (bTB) in cattle, the world’s most neglected zoonotic disease that needs urgent attention, especially in developing countries [1, 2]. The largest disease burden probably occurs in poor, marginalized, rural communities living in close proximity to animals, and with reduced access to safe food and health care. In 2017, Olea-Popelka and co-authors raised awareness for the worldwide importance of bTB, in the African continent, where insufficient surveillance, testing and traditional ways of rearing and consuming cattle may be responsible for under-notification of this zoonotic disease [6]. An important percentage of cases diagnosed as TB and attributed to Mycobacterium tuberculosis infection may be bTB. The movement of animals has most probably been the main reason for the spread of M. bovis both within the same country as well as cross-borders [4, 8, 9]
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