Exposure of wildlife to anthrax in Kruger and Etosha National Parks and the effect of haemoparasite coinfections

Abstract

Anthrax has a global distribution and it is enzootic in Kruger National Park (KNP) in South Africa and Etosha National Park (ENP) in Namibia. These parks share some similarities such as hosts species and both have endemic and non-endemic areas, but host species differ in their susceptibility between the parks. We measured the presence of anti-PA antibodies in zebra and kudu from both parks using ELISA and also their ability to neutralize anthrax lethal toxin vis-à-vis haemoparasite coinfections detected with reverse line blot probes of Theileria, Babesia, Anaplasma and Ehrlichia. It was found that kudus in KNP had higher titres and proportion (95%) of positive animals than ENP (40%). ENP zebras had higher titres and proportions of positive animals (83%) than those of KNP (63%). Animals in anthrax endemic areas in KNP had higher titres than those in non-endemic areas, but this was not so in ENP. ENP kudus and KNP zebras showed better and higher proportion of neutralization. Animals positive to haemoparasites (Theileria, Babesia, Ehrlichia and Anaplasma) showed a significant difference between the kudu in KNP (100%) compared to 70% in ENP, while all ENP zebra (100%) tested positive compared to 84.6% KNP zebra. An increase in toxin neutralization was significantly associated with less likelihood of infection with haemoparasites in zebras. In summary, this study shows that rarity is largely a function of resistance toward anthrax, which could have emanated from both the dose of infection and the interval between exposures and the interplays of other infections in the host.