Analysis of the haemagglutinin gene of current wild-type canine distemper virus isolates from Germany

Abstract The haemagglutinin (H) gene sequences from three wild-type canine distemper viruses (CDV) isolated during 1994–1995 were sequenced to determine whether contemporary strains had undergone significant genetic changes relative to the currently used vaccine strains. The new isolates were closely related to each other (>99%) and displayed about 90–91% sequence homology to the Onderstepoort and Convac vaccine strains. There were one to four additional potential glycosylation sites compared to the vaccine strains which were also present in a German dog CDV isolate dating from 1990. However, only a very slight reduction in neutralizing titre against the new isolates was found when compared with the Onderstepoort and Rockborn vaccine strains. Cysteine and proline residues were well conserved indicating a conserved three dimensional structure for the protein. By phylogenetic analysis the recent isolates showed a narrow clustering close to the previous canine isolates indicating a linear pattern of evolutionary changes. A comparison with published CDV H gene sequences suggested the presence of different lineages of CDV on a global scale and possible cocirculation of more than one genotype of CDV.