Rabies viruses are known to be able to infect a broad range of warm-blooded animals. In
South Africa the disease is maintained in different animal species including dogs, jackals, bateared
foxes and a variety of members of the viverridae family. These include the different
mongoose species (principally the yellow mongoose), genets, suricates and a variety of small
carmvores. The antigenic variation within the nucleoprotein gene has previously been
investigated in efforts to characterise various isolates of rabies viruses in southern Africa. It
was noted that two antigenically distinct groups are cocirculating in the country. In this study, the investigation into the epidemiology of rabies in South Africa was extended by molecular
genetic analysis of a large number of isolates from wildlife and domestic animal hosts.
Geographically and temporally distinct rabies viruses were previously studied by comparative
nucleotide sequence analysis of DNA fragments encompassing the cytoplasmic domain of the
glycoprotein and the G-L intergenic region. Based on this analysis two main rabies virus
groups were identified. Members of the first group infect canid host species and are closely
related to the European rabies strains, while the viruses belonging to the second group
circulate within different viverrid species. Although isolates of mainly mongoose origin were
initially analysed, considerable heterogeneity within this group was evident. The current study
was consequently undertaken to include rabies virus isolates from other viverrid host species.
Following the same approach as the previous investigators (Nel et al., 1993 & von Teichman
et al., 1995) four genetically distinct clusters were indicated within the viverrid lineage. These
clusters corresponded closely to the geographic origin of the virus isolates independent of
specific viverrid host. The results suggest genetic divergence and independent evolution of the
viverrid viruses within geographically isolated regions. Spillover or cross-infection, where a
viverrid virus is recovered from a canid host and vice versa, could not be attributed to a new
rabies virus and were most likely initiated by interspecies transmission events. These results
suggest little modification of the virus following infection of an atypical host.
A phylogeny of the rabies virus variants in southern Africa was established based on sequence
variation within the abovementioned genome regions. Although such an approach is most
informative when compared to other methods, it is time-consuming and laborious. The use of
strain-specific oligonucleotides was therefore investigated for rapid strain differentiation. Two
oligonucleotides were designed based on the nucleotide sequences of the cytoplasmic domain
of the glycoprotein and the G-L intergenic region. These oligonucleotides together with a
common downstream primer were used to amplify DNA fragments of characteristic size,
allowing for discrimination between the two rabies biotypes.
Afrikaans: Dit is bekend dat die hondsdolheidsvirus verskeie warmbloedige diere kan infekteer. In suider
Afrika word die siekte onderhou in gasheer spesies soos honde, jakkalse, bakoorvosse en lede
van die Viverridae familie. Dit sluit verskeie meerkat spesies (hoofsaaklik die
witkwasmuishond), kleinkolmuskejaatkat, stokstertmeerkat en 'n verskeidenheid klein
karnivoorspesies in. Die antigeniese variasie binne die nukleoprotei"en geen is voorheen
aangewend in 'n poging om hondsdolheidsvirus-isolate in suidelike Afrika te karakteriseer.
Uit hierdie ondersoek het dit geblyk dat daar twee antigenies-onderskeibare virusgroepe in die
land sirkuleer. In hierdie studie word die ondersoek na die epidemiologie van hondsdolheid in Suid-Afrika uitgebrei deur middel van genetiese analise van 'n groot aantal isolate afkomstig
vanaf wilde- sowel as huishoudelike diere.
Die genetiese variasie van geografies- en temporaal-verwyderde isolate is vantevore deur
middel van vergelykende nukleotiedvolgorde-analise ondersoek. Hierdie vergelykings het die
nuletensuurvolgordes van die sitoplasmiese gebied van die glikoprote1en en die G-L
intergeniese gebied ingesluit. Hierdie analise het twee hoofgroepe hondsdolheidsvirusse
aangedui. Lede van die eerste groep infekteer canid gasheer spesies en is nou verwant aan die
Europese hondsdolheidsvirusse, terwyl die tweede groep binne verskillende viverrid spesies
sirkuleer. Alhoewel daar aanvanklik virus isolate vanuit hoofsaaklik die witkwasmuishond
ondersoek is, was daar heelwat heterogenisiteit binne die viverrid virusse gevind. Gevolglik is
hierdie studie onderneem om hondsdolheidsvirusse vanaf antler viverrid gashere in te sluit.
Deur gebruik te maak van dieselfde benadering as vorige navorsers (Nel et al., 1993; von
Teichman et al., 1995) is vier geneties onderskeibare groepe binne die viverrid stamboom
aangetoon. Hierdie groepe het nou ooreengestem met die geografiese oorsprong van die virus
isolate, onafhanklik van 'n spesifieke gasheer. Hierdie resultate dui daarop dat onafhanklike
ewolusie van die viverrid virusse binne ge1soleerde lokaliteite plaasvind. Kruis-infeksie, waar
viverrid virusse canid gashere en omgekeerd infekteer, kon nie toegeskryf word aan 'n nuwe
hondsdolheidsvirus me. Hierdie verskynsel word vermoedelik deur interspesie oordraag
gebeure ge'inisieer.
'n Filogenetiese verwantskap van hondsdolheidsvirusse in suider Afrika is bepaal op grond van
van die nuleotiedvolgorde variasie in bogenoemde genomiese gebiede. In vergeleke met
antler metodes, is hierdie benadering baie informatief, maar dit kan tydrowend en moeisaam
wees. Die gebruik van ras-spesifieke voorvoerders is daarom ondersoek as 'n alternatiewe
metode vir differensiasie. Twee voorvoerders is ontwerp gebaseer op die volgordes van die
sitoplasmiese gebied van die glikoprote1en en die G-L intergeniese gebied. Deur hierdie
voorvoerders tesame met 'n gemeenskaplike stroom-af voorvoerder te gebruik word DNA
fragmente van karakteristieke groottes geamplifiseer. Hierdie benadering voorsien dus 'n
makliker manier vir onderskeiding tussen die twee virus groepe.
