Occurrence of Ehrlichia ruminantium and Rickettsia africae in Amblyomma variegatum ticks in selected regions of Zambia

Abstract

This study was conducted in Zambia and the main objective was to determine the prevalence of Ehrlichia ruminantium and Rickettsia africae in adult Amblyomma variegatum ticks in selected regions of Zambia. A total of 567 adult A. variegatum ticks were collected from three regions of Zambia (eastern, central and western), following an east-west transect across the country. Ticks were most abundant in the western region, less abundant in the eastern region, and the lowest abundance was found in the central region. Ticks were identified morphologically using a stereoscopic microscope. In all three regions, only A. variegatum was found. The ticks’ infection rates of E. ruminantium and R. africae were determined using polymerase chain reaction (PCR) targeting pCS20 fragment for E. ruminantium, and ompA gene for R. africae. Overall prevalence of E. ruminantium was determined to be 18.52% (9.4% western, 35.4% eastern, and 18.8% central regions). The overall prevalence of R. africae was found to be 36.07% (23.3% western, 56.1% eastern and 41.7% central regions). The presence of the vector and its associated disease pathogens is indicative of the occurrence of heartwater and African tick bite fever (ATBF) in Zambia, with the prevalence of both pathogens probably being underestimated before, and not accurately associated with disease and/or mortality in livestock and humans, respectively. In light of the results obtained in the present study, it would be advisable for measures to be put in place by veterinary and medical authorities in order to appropriately address these important issues. Given the veterinary importance of heartwater and the medical pertinence of ATBF, this seems to be a perfect example, where a One Health framework approach may produce synergic beneficial results.