Epidemiological baseline of Brucella spp. in South African wildlife

Brucellosis is a globally significant zoonotic disease, yet its ecology in wildlife remains poorly understood. In this study, we investigated the circulation of Brucella spp. in a wide range of wild mammals from multiple protected areas in South Africa. Organ and serum samples from 722 animals representing 23 species were analyzed employing a conservative diagnostic strategy, combining serology (rose bengal test confirmed by indirect ELISA) and four PCR-based assays in series, to maximize specificity and interpretative solidity. Molecular detection revealed Brucella spp. DNA in several atypical host species, including plains zebra, hippopotamus, African elephant, giraffe, warthog, cheetah, and African wild dog, expanding the known host range. In Greater Kruger National Park, African buffalo exhibited high seroprevalence (24/106; 23%, CI: 15-32%) and even higher molecular prevalence (29/57; 51%, CI: 37-64%), supporting their role as a primary wildlife reservoir for B. abortus in the region. One B. abortus isolate cultured from the spleen of a zebra and characterized by multiloci variable number of tandem repeat analysis (MLVA) showed genetic relatedness to South African buffalo and South American cattle strains. Co-infections with B. abortus and B. melitensis were identified in 17 animals across seven species. Notably, B. melitensis was detected in species (elephant, hippopotamus, zebra) not typically associated with small ruminants, suggesting complex interspecies transmission dynamics. Our findings underscore the limitations of serological testing and highligts the value of molecular diagnostics in understanding the epidemiology of Brucella spp. in South Africa. The detection of B. abortus and/or B. melitensis DNA in a range of wildlife species, including carnivores and megaherbivores, emphasises the need for integrated One Health surveillance approaches to enhance understanding of the disease's life cycle and transmission dynamics.