Mapping the Potential Geographic Distribution of the Heartwater Disease Vector Tick Amblyomma hebraeum Under Climate Change

Abstract

Amblyomma hebraeum is a tick species of veterinary importance because it is a major vector of Ehrlichia ruminantium, the causative agent of heartwater disease. This species infests livestock in southern African regions and is a three-host species of veterinary importance. Maximum entropy algorithm (MaxEnt) modeling was used to predict the potential distribution of A. hebraeum. The MaxEnt model performed better than random with an average test area under the curve (AUC) value of 0.94, and model predictions were significantly better than random, giving AUC ratios above the null expectations in the partial receiver operating characteristic (pROC) analyses (p < 0.001). A set of five variables was selected for the species from 19 bioclimatic variables based on correlation analysis. The study showed that the current distribution of A. hebraeum is estimated to occur across coastal regions of the Eastern Cape and KwaZulu-Natal provinces in South Africa, Swaziland, southern Mozambique, eastern Zimbabwe, and eastern Botswana. Temperature seasonality (Bio 4) had the highest effect on the distribution of this species. The environmentally suitable habitat for A. hebraeum increased with decreasing temperature seasonality (Bio 4). Transferring the models to future conditions showed a decrease in suitable habitats for this species under changing climate. These results have public health implications and can be used for making control planning decisions in areas suitable for this vector across its geographical distribution.