The spores of the soil-borne bacterium, Bacillus anthracis, which causes anthrax are highly
resistant to adverse environmental conditions. Under ideal conditions, anthrax spores can
survive for many years in the soil. Anthrax is known to be endemic in the northern part of
Kruger National Park (KNP) in South Africa (SA), with occasional epidemics spreading
southward. The aim of this study was to identify and map areas that are ecologically suitable
for the harboring of B. anthracis spores within the KNP. Anthrax surveillance data and
selected environmental variables were used as inputs to the maximum entropy (Maxent)
species distribution modeling method. Anthrax positive carcasses from 1988±2011 in KNP
(n = 597) and a total of 40 environmental variables were used to predict and evaluate their
relative contribution to suitability for anthrax occurrence in KNP. The environmental variables
that contributed the most to the occurrence of anthrax were soil type, normalized difference
vegetation index (NDVI) and precipitation. Apart from the endemic Pafuri region,
several other areas within KNP were classified as ecologically suitable. The outputs of this
study could guide future surveillance efforts to focus on predicted suitable areas for anthrax,
since the KNP currently uses passive surveillance to detect anthrax outbreaks.
S1 Table. Worldclim variables used in Maxent model.
S2 Table. Overview of environmental data used in Maxent indicating the variables, type of
data and source.
S1 Fig. Spatially unique cases of Bacillus anthracis and the predicted suitability for B.
S2 Fig. Twelve environmental variables used in the final Maxent model.