Ecological suitability modeling for anthrax in the Kruger National Park, South Africa

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. anthracis occurrence.S2 Fig. Twelve environmental variables used in the final Maxent model.http://www.plosone.orgam2018Production Animal StudiesVeterinary Tropical Disease

Ecological suitability modeling for anthrax in the Kruger National Park, South Africa.

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

Threshold point values (>0.8) for the twelve environmental variables and the three most suitable areas identified by the model in Kruger National Park for <i>Bacillus anthracis</i> occurrence (see Fig 1).

<p>Threshold point values (>0.8) for the twelve environmental variables and the three most suitable areas identified by the model in Kruger National Park for <i>Bacillus anthracis</i> occurrence (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0191704#pone.0191704.g001" target="_blank">Fig 1</a>).</p

Accuracy metrics for the predicted distribution for Maxtent model using 12 variables.

<p>Accuracy metrics for the predicted distribution for Maxtent model using 12 variables.</p

Threshold point values (>0.8) for the twelve environmental variables and the three most suitable areas identified by the model in Kruger National Park for <i>Bacillus anthracis</i> occurrence (see Fig 1).

<p>Threshold point values (>0.8) for the twelve environmental variables and the three most suitable areas identified by the model in Kruger National Park for <i>Bacillus anthracis</i> occurrence (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0191704#pone.0191704.g001" target="_blank">Fig 1</a>).</p

Environmental variables used for the final Maxent model.

<p>Environmental variables used for the final Maxent model.</p