Bacillus anthracis diversity in Kruger National Park

The Kruger National Park (KNP), South Africa, has a recorded history of per iodic anthrax epidemics causing widespread disease among wild animals. Baci llus anthracis is the causative agent of anthrax, a disease primarily affec ting ungulate herbivores, Worldwide there is little diversity among B. anth racis isolates, but examination of variable-number tandem repeat (VNTR) loc i has identified six major clones, with the most dissimilar types split int o the A and B branches, Both the A and B types are found in southern Africa , giving this region the greatest genetic diversity of B. anthracis worldwi de, Consequently, southern Africa has been hypothesized to be the geographi c origin of B. anthracis. In this study, we identify the genotypic types of 98 KNP B, anthracis isolates using multiple-locus VNTR analysis. Two major types are evident, the A branch and the B branch. The spatial and temporal distribution of the different genotypes indicates that anthrax epidemic fo ci are independent, though correlated through environmental cues, Kruger B isolates were found on significantly higher-calcium and higher-pa soils tha n were Kruger type A. This relationship between genotype and soil chemistry may be due to adaptive differences among divergent anthrax strains. While this association may be simply fortuitous, adaptation of A types to diverse environmental conditions is consistent with their greater geographic dispe rsal and genetic dissimilarity.