Molecular characterisation of Bacillus anthracis involved in outbreaks in the Zambezi basin

Abstract

Outbreaks of anthrax in livestock and wildlife have become a seasonal occurrence in Zambia. Consequently, the disease caused by Bacillus anthracis, has also been shown to be a classical zoonoses as almost with every outbreak, there is human involvement, where they get infected through contact and ingestion of contaminated meat/products. Accordingly, the disease has a direct effect on the livelihoods of the people living in the known endemic areas through which the socio-anthropogenic as well as socioeconomic determinants of the disease are observed. This scenario has been observed to occur almost annually in two ecosystems along the Zambezi basin, that is the Upper and Lower Zambezi basins. Thus, the aim of this study was to characterize and determine the genetic diversity of B. anthracis causing these mortalities in animals and humans in the two different sites of the Zambezi basin through molecular characterization. The first samples were collected from four (4) districts, located in the Upper Zambezi Basin, of Western Province of Zambia where livestock, particularly cattle, and human beings were infected following outbreaks in 2000, 2013 through to 2016. The second collection was from outbreaks in the Lower Zambezi basin during 2012, where predominantly wildlife was infected with concurrent outbreaks in human populations. Using the agarose gel methodology, multiple-locus variable-number of tandem repeat analysis (MLVA) based on 11 markers indicated 3 genotypes amongst 28 B. anthracis strains from Zambia in this study with one dominant genotype i.e. the Ancient A (Aβ) sublineage of the A -clade (consisting of 85.7% (24/28)). This indicate clonality of B. anthracis strains in this study from Zambia circulating in livestock, wildlife, humans and surrounding environments in the two regions.