Molecular characterisation and host specificity of canine distemper virus in selected wild carnivores of South Africa

Abstract

Canine distemper virus (CDV) has emerged as a significant disease of wildlife, is highly contagious and readily transmitted between susceptible hosts. Initially described as an infectious disease of domestic dogs, it is now recognised as a global multi-host pathogen, infecting and causing mass mortalities in a wide range of carnivore species. The last decade has seen the negative effect of numerous CDV outbreaks in various wildlife populations. Prevention of CDV infection requires a clear understanding of the potential as well as the dynamic pathways CDV uses to gain entry to its host cells and its ability to initiate viral shedding and disease transmission. Additionally, vaccination failure in CDV-infected wildlife is not uncommon, with several cases of disease outbreaks reported in vaccinated individuals. More studies on the genetic characteristics of CDV is thus required to evaluate the effectiveness of current CDV vaccines and to determine if there is a need to develop new vaccines against emergence of novel CDV strains. The first chapter is a review on recent research conducted on CDV infection in wildlife, including the latest findings on the causes of host specificity and cellular receptors involved in distemper pathogenesis. This is followed by a chapter on the whole genome sequence analyses of three CDV vaccines (Nobivac, Onderstepoort and Bucharest) and wild-type strains, isolated from African wild dog (Lycaon pictus) and spotted hyena (Crocuta crocuta). Each gene region was assessed through phylogenetic analyses and was evaluated for their usefulness in distinguishing strain diversity. Results showed that these two wild-type strains belong to the South African lineage, and all three vaccine strains to America I. Little is known about the CDV strains circulating in South Africa and these results constitute the first genomic sequences reported from isolates in South Africa.