Molecular characterization of carrier rabies isolates

Abstract

We compared the genomes of nine dog rabies virus isolates using two molecular methods. The viruses used in the comparison included three Ethiopian rabies strains from carrier dogs, a street strain from a rabid dog from the same geographic area, two saliva isolates made from an experimentally infected carrier dog, the virus isolated from the tonsil of this carrier dog at necropsy, and two laboratory strains. We produced overlapping polymerase chain reaction (PCR) segments spanning 97% of the genome. Restriction analysis of these PCR products with AvaII, Bcll, and BamHI detected 39 variable sites representing 668 nucleotides (nt) or 5.5% of the genome. We also compared the DNA and the deduced peptide sequences of a 200-nt segment of the 3' end of the rabies nucleoprotein gene. Previous work with these Ethiopian carrier viruses and the endemic street strain had failed to show any differences among them. Both restriction mapping and sequence analysis of 200 nt of the nucleoprotein gene allowed us to individually identify these isolates. Phylogenetic analyses of these data sets showed only the two saliva isolates of the experimentally infected carrier dog to be identical. Each of the viruses in this study, including the one isolated from the tonsil of the experimentally infected carrier dog, could be distinguished by these techniques.