VP2 based genotyping of canine parvo virus
Abstract
The objective of the current study was to screen the faecal samples from suspected dogs for canine parvo virus infection and also to monitor the predominant genotype circulating in Haryana and nearby areas. Screening was performed based on the partial VP2 gene. Genotyping was based on genotype specific primers to differentiate CPV2a from CPV2b. PCR and RFLP was performed to differentiate vaccine strain from field strain. Primer walk technique was done based on overlapping sequence primers to generate complete coding sequence of canine parvo virus. Sequencing was performed for cloned isolates. Multiple sequence alignment and Phylogenetic tree construction also done.
Total of 140 samples collected, 72 were found to be positive on the basis of VP2 gene based conventional PCR. Genotyping was done using genotype specific primers. Out of 72 screened positive, 62 were found to be CPV2b, whereas the rest 10 found to be CPV2a. Hence the predominant field strain circulating in Hisar, Haryana and nearby areas was concluded as CPV2b. A single case of vaccinated dog was shown positive by VP2 gene based screening. Since the vaccine strain (CPV 2) and field strain (CPV 2a/2b) are different, the cross protection may be negligible. Further PCR and RFLP were done to differentiate vaccine strain (CPV2) from field strain (CPV2a/2b) by RsaI enzyme and the resultant pattern of digested fragment confirmed the significant difference between vaccine and field strain. Along with immunological and vaccine challenge studies, the lack of vaccine potential may be confirmed. The above study gives an insight for reconsidering the vaccine formulation with the incorporation of currently circulating predominant strain, so that better protection can be achieved. The multiple alignment and Phylogenetic tree construction of Hisar CPV isolate was done against CPV isolates from various geographical locations based on VP2 gene. The Phylogenetic tree results showed that the Hisar CPV isolate was closely related with that of china, Taiwan and Uruguay and formed a separate Claude. Hence the Hisar CPV strain might have been evolved from eastern Asian countries.