Infectious bursal disease virus (IBDV) remerged frequently in Qualubyia was the cause of serious economic losses. Twenty field samples were collected from broiler chick farms in different localities of the governorate in January 2015, subjected for isolation on specific pathogen free-embryonated chicken eggs (SPF-ECE), detection using AGID and RT-PCR. Ten samples showed positive results with egg isolation, AGID and RT-PCR. Sequence analysis and characterization of the variable region of VP2 gene purified
from the PCR product showed many amino acid substitutions that may affect IBDV antigenicity and virulence. Comparative phylogenetic analysis based on the sequence of the hypervariable region of VP2 gene clustered the isolated IBDV at a distance from the other reference IBDV from Egypt, Europe and other
vaccinal strains. It was concluded that substitution mutations observed with the hypervariable region of VP2 gene of the isolated IBDV could affect the virus antigenicity and further studies on the efficacy of vaccines used locally against this variant IBDV strain have to be investigated |
