The effect of climate change on the distribution of Amblyomma hebraeum and heartwater in South Africa

Abstract

Historically Amblyomma hebraeum has been found in the north-eastern part of South Africa and along the coastal belt stretching to the Eastern Cape area. A change already noted in the past 20 years has been the increase in distribution area in the Eastern Cape, which now includes a larger inland area. It has been postulated that climate change has brought about a change in the distribution of A. hebraeum and subsequently, its potential tick-borne pathogens (TBP), Ehrlichia ruminantium and Rickettsia africae, in South Africa and that the effects of climate change may lead to further distribution changes in future. Habitat suitability modelling using Maxent software demonstrated that the distribution of A. hebraeum has altered compared to previous predictions done 15 years ago and that by the year 2065, most of the central and eastern parts of South Africa are predicted to have a high habitat suitability index for its presence. This indicates that the potential presence of diseases caused by E. ruminantium and R. africae would have to be considered in these previously unaffected areas when animals or humans show signs of illness. This expanded distribution of A. hebraeum and its TBP could have a substantial health and economic impact in South Africa.