Mongoose rabies in southern Africa: a re-evaluation based on molecular epidemiology

Relative to the developed world, rabies has been poorly studied in the vast African continent. The southern African countries of Zimbabwe and South Africa, however, are known to sustain a great diversity of lyssaviruses, with large biological variations amongst genotype 1 (rabies viruses) at present more apparent here than elsewhere on the continent. One recognized biotype of rabies virus in the subcontinent appears to be specifically adapted to a variety of mongooses, belonging to the Viverrinae subfamily (family Herpestidae) and are commonly referred to as viverrid viruses, although the term mongoose rabies would be more correct, considering the taxonomic status of the host species involved. It was our objective to study the genetic relationships of 77 rabies virus isolates of this mongoose biotype, isolated in South Africa and Zimbabwe, towards elucidation of the molecular epidemiology of this interesting group of African viruses. In our study of a 592 nucleotide sequence encompassing the cytoplasmic domain of the glycoprotein and the G-L intergenic region of the viral genomes, we provide the first comprehensive data on the molecular epidemiology of these viruses and indicate a history of extended evolutionary adaptation in this geographical domain. The molecular epidemiological observations reported here are highly unlikely to be limited to the small geographical areas of South Africa and Zimbabwe and illustrate the need for lyssavirus surveillance in the rest of sub-Saharan Africa and throughout the entire continent.

Characterization of pigmented methylotrophic bacteria which nodulate Lotononis bainesii

Root nodule isolates from a shrubby legume, Lotononis bainesii, were characterized by 16S rRNA gene sequencing and morphologically by substrate utilization patterns. The symbiotic genome of these isolates was analysed by partial sequencing of the nifH gene. Based on the results of numerical taxonomy, the isolates formed a closely related cluster, showing no correspondence to any of the known rhizobial clusters. Analysis of nearly full-length 16S rDNA sequences demonstrated that these isolates were related to Methylobacterium nodulans (SY et al., 2001). In the absence of nifH sequence data for the genus Methylobacterium, the nifH phylogeny showed these isolates to be related to Azospirillum brasilense. The facultative methylotrophic nature of these isolates was also demonstrated by their ability to grow in the presence of methanol as a sole carbon source.

A nucleotide-specific polymerase chain reaction assay to differentiate rabies virus biotypes in South Africa

Antigenic and nucleotide sequence analyses have shown that two distinct biotypes of rabies virus are circulating in South Africa. One of these typically infects members of the family Canidae, while the other comprises a heterogeneous group of apparently indigenous viruses, infecting members of the Viverridae family. In recent times, it has become evident that a considerable amount of cross-infection may occur and the manifestation of viverrid rabies in non-viverrid animals in particular appears to have become more commonplace. Consequently, the need to rapidly distinguish between rabies virus biotypes has become increasingly important in efforts to monitor the epidemiology of rabies in the southern African region. In this study, a nested polymerase chain reaction (PCR) assay was developed to distinguish between these two groups of rabies viruses. Consensus oligonucleotides were used to amplify the cytoplasmic domain of the rabies virus glycoprotein and the adjacent intergenic region. The resultant amplicon was subsequently used as template in second round heminested PCR in the presence of type-specific primers, thereby successfully generating amplicons of characteristic size for each biotype.