Strain differentiation of canine distemper virus by reverse transcriptase polymerase chain reaction and restriction fragment length polymorphism analysis

To detect CDV RNA in clinical samples and differentiate prevailing CDV virulent strains affecting susceptible animals from attenuated vaccine strains, we performed RT-PCR, RFLP, and sequencing. CDV specific primers were generated from the middle part of nucleocapsid gene. The expected size of PCR products, 519 bp, was observed in tissues of Jindo dog, poodle dog, badger, fourteen of nineteen blood samples as well as 5 vaccine strains including domestic and imported products. The PCR products obtained from tissues and PBMCs of infected animals were digested to 317- and 202-bp fragments by Bam HI, but the products obtained from four of five vaccine strains and Lederle strain were not digesed by Bam HI. Only one vaccine strain of which the PCR products were digested by Bam HI was confirmed as imported vaccine, modified Synider Hill strain. Based on seqencing data obtained from the 519-bp products, it was confirmed that Bam HI restriction site tends to be conserved in field isolates compared to the commercially available attenuated vaccine strains. Partial nucleotide sequences of CDV NP gene obtained from tissues of Jindo dog, poodle and badger shared 100% homology each other, whereas the nucleotide sequences showed 96.3, 96.5, 93.6 and 93.4% homology with Yanaka (virulent), Han95 (virulent), Lederle (attenuated) and Onderstepoort (attenuated) strain, respectively.