MOLECULAR CHARACTERIZATION OF INFECTIOUS BURSAL DISEASE VIRUSES FROM THE RECENT OUTBREAKS IN POULTRY IN HARYANA, INDIA

The present study was conducted to characterize the infectious bursal disease virus (IBDV) by reverse transcription- polymerase chain reaction (RT-PCR). Detection of IBDV by RT- PCR was carried out in bursal samples from 30 commercial broiler chicken flocks and four vaccine strains by amplifying the hypervariable region of VP2 gene. The IBDV was detected in bursal samples from 28 out of 30 flocks and in all the four vaccine strains. Phylogenetic analysis based on the nucleotide sequencing of VP2 gene of 10 IBDVs revealed that nine were of very virulent nature due to the presence of 795G, 827T, 833C, 857C, 897A, 905T, 908T and 1011A specific to vvIBDV strains. The amino acids isoleucine at positions 242, 256 and 294, glutamine at position 253 and serine at position 299 were also observed in these nine IBDVs. Amino acid changes from isoleucine to threonine at position 272 in one IBDV (HR/9097/07), asparagine to aspartic acid at position 279 in four IBDVs (HR/8664/07, HR/10277/08, HR/10612/08 and HR/8044/07), glutamic acid to alanine at position 300 in two IBDVs (HR/8664/07 and HR/ 10277/08) and valine to serine at position 357 in one IBDV (HR/8044/07) were also observed. The remaining one strain had valine, leucine and asparagine at positions 242, 294 and 299, respectively; all of which are features of a classical strain. Nucleotide and deduced amino acid sequencing revealed the presence of vvIBDV strains in commercial broiler flocks and also suggested the continued genetic drift.