This study was conducted to estimate the prevalence of IBD in broiler farms from different localities in
different Governorates; AlQalubia, AlGharbia, AlMenofia and ALBehera and also to make further
characterization of the obtained strains through nucleotide sequencing then evaluate the pathogenicity
of the strain in SPF ECE and commercial broiler chicks. Fifteen out of total 32 (46.87%) bursal samples
showed 620 bp amplicon size of HVR of VP2 when tested with RT-PCR. The nucleotide sequencing
classified 2 strains as vvIBDV and one was similar to classical attenuated vaccines. The vvIBDV strain
resulted in 100 % mortality of inoculated embryos with moderate to severe congestion of the body,
cranial hemorrhage, congested and greenish liver with necrotic foci. The CAMs showed thickening with
petechial hemorrhage. The experimental infection with (IBDV_ EGY 2018/N23) isolate was assessed
in vaccinated groups with hot, intermediate and hot + intermediate vaccines and unvaccinated 25 days
old Cobb broiler chicks; the c+ve group showed a significant difference in RWBF and cumulative bursal
lesion in comparison with c–ve group. It recorded higher MSI than c–ve. All vaccinated groups showed
significant increase in Abs titer when compared with non-vaccinated one and the hot vac. group
recorded the highest titer. They also showed non-significant difference in RWBF and cumulative bursal
lesion score in comparison to c-ve one at 10 dPI and lower MSI than c+ve but the hot + intermediate
vac. group recorded the lowest lesion score and MSI. This study concluded the reemergence and
circulation of vvIBDV in spite of the intensive vaccination strategies.