Infection Rates and Characterisation of Rickettsia africae (Rickettsiaceae) Detected in Amblyomma Species from Southern Africa

Tick-borne rickettsioses are considered among the oldest known vector-borne zoonotic diseases. Among the rickettsiae, <i>Rickettsia africae</i> is the most reported and important in Africa, as it is the aetiological agent of African tick bite fever (ATBF). Studies describing the prevalence of <i>R</i>. <i>africae</i> in southern Africa are fragmented, as they are limited to small geographical areas and focused on <i>Amblyomma hebraeum</i> and <i>Amblyomma variegatum</i> as vectors. <i>Amblyomma</i> spp. ticks were collected in Angola, Mozambique, South Africa, Zambia and Zimbabwe during the sampling period from March 2020 to September 2022. <i>Rickettsia africae</i> was detected using the <i>ompA</i> gene, while characterisation was conducted using <i>omp</i>, <i>ompA</i>, <i>ompB</i> and <i>gltA</i> genes. In total, 7734 <i>Amblyomma</i> spp. ticks were collected and were morphologically and molecularly identified as <i>Amblyomma eburneum</i>, <i>A</i>. <i>hebraeum</i>, <i>Amblyomma pomposum</i> and <i>A</i>. <i>variegatum</i>. Low levels of variability were observed in the phylogenetic analysis of the <i>R. africae</i> concatenated genes. The prevalence of <i>R</i>. <i>africae</i> ranged from 11.7% in South Africa to 35.7% in Zambia. This is one of the largest studies on <i>R</i>. <i>africae</i> prevalence in southern Africa and highlights the need for the inclusion of ATBF as a differential diagnosis when inhabitants and travellers present with flu-like symptoms in the documented countries.