Cloning and sequence analysis of haemagglutinin gene of canine distemper virus in Guangdong area

Objective  To perform etiological investigation of canine distemper virus (CDV) infection in dogs from Guangzhou and Dongguan, moniter the genetic evolution of canine CDV, and provide a data basis for the prevention and control of canine distemper (CD).

Method  Seventeen CDV positive samples were identified from dogs with CD symptoms. The haemagglutinin ( H ) genes of these wild strains were obtained by RT-PCR, and the H gene sequences were compared and analyzed through bioinformatics approach.

Result  The similarities of nucleotide and amino acid sequences of H genes from 17 CDV strains were 97.4% to 100.0% and 97.5% to 100.0%, respectively. Compared with vaccine strains such as Onderstepoort, Lederle and Convac, the similarities of nucleotide and amino acid sequences of H genes from these CDV strains were 90.3% to 91.5% and 89.4% to 90.8%, respectively. Phylogenetic tree analysis showed that 17 CDV wild strains belonged to Asia I subtype and were distant from the vaccine strains. The identified wild strains had evolved to containing nine potential N-glycosylation sites.

Conclusion  Asia I CDV is still an epidemic subtype in this region and this subtype is stable, but it has formed a certain evolutionary distance and a large number of mutations compared with vaccine strains. Therefore, it is of great significance to continue to monitor the evolution of CDV in dog populations.