Molecular epidemiology of rabies in northern South Africa and southern Zimbabwe demonstrates an epidemiological complexity that involves domestic dogs and jackals (Canis mesomelas)

Abstract

Canine rabies was noted in South Africa from 1950 and the domestic dog has from that time been recognized as the primary host species and the main vector transmitting the rabies virus (RABV) to humans. Canis mesomelas , has been recognized as the rabies host species in northern South Africa since 1954, following the initial outbreaks in domestic dogs. The emergence of rabies in jackals has debilitated the elimination of rabies and has also raised concerns about the effectiveness of the rabies control approaches that target only domestic dogs for rabies vaccination. This study was aimed at determining the transmission dynamics of the RABV between domestic dogs and C. mesomelas in the northern region of South Africa including Limpopo, Mpumalanga and North West provinces. In addition, the study was aimed at establishing phylogenetic relationships of rabies viruses recovered from these two host species from northern South Africa and southern Zimbabwe. The central question addressed in this investigation was whether C. mesomelas is an emerging maintenance host species of rabies in South Africa. A panel of 135 rabies viruses recovered from the two host species from 1980 to 2006 were characterised by nucleotide sequencing of the cytoplasmic domain of the glycoprotein gene and the non-coding G-L intergenic region. Through phylogenetic analysis of the nucleotide sequence data of the viruses included in this investigation, seven viral lineages were identified in northern South Africa. Among the lineages identified, a distinct lineage composed of exclusively C. mesomelas RABV isolates was discovered in the bushveld ranches in western Limpopo, demonstrating that this jackal species is capable of sustaining rabies cycles independent of domestic dogs. Three viral lineages were composed of a mixture of RABV isolates from both the species, highlighting the ease of exchange of RABV between the two canid species. As part of this study, a new dog rabies lineage that emerged in 2005 and was associated with an outbreak in north eastern Limpopo, was also discovered. The last two lineages were composed of rabies viruses primarily from domestic dogs in the Mpumalanga province. The recent dog lineage in north eastern Limpopo was shown to be genetically related to canid rabies viruses from southern Zimbabwe, indicating that this lineage could have been introduced from Zimbabwe. The re-emergence of dog rabies in Limpopo highlighted the importance of continuous and sustained animal vaccination programs. Furthermore it has re-emphasized the importance of multinational collaboration and control of animal movement across national borders to control the dissemination of rabies. The fact that C. mesomelas are capable of sustaining rabies infection cycles independent of domestic dogs indicates that despite the fact that parenteral immunization of domestic dogs can eliminate rabies in dogs, C. mesomelas are likely to re-infect domestic dogs as the underlying enzootic exists in this wild canid species and this poses a serious threat to public health. Hence it is proposed that wildlife rabies control strategies that are in synergy with the existing domestic animal vaccination for effective control of rabies in South Africa should be considered.