Moemen A. Mohamed

Genetic Characterization of Infectious Bursal Disease Viruses Associated with Gumboro Outbreaks in Commercial Broilers from Asyut Province, Egypt

Ten infectious bursal disease virus (IBDV) field strains were isolated from 15 broiler flocks located in various parts of Asyut, Egypt. Seven strains were subjected to comparative sequencing and phylogenetic analyses to help provide optimal control program for protection against IBDV infection. Sequence analysis of a 530 bp hypervariable region in the VP2 gene revealed that the rate of identity and homology was around 95.6~99.1%. Sequence characterization revealed the 7 strains identified as vvIBDV with the four amino acids residues typical of vvIBDV (242I, 256I, 294I, 299S). The BURSA-VAC vaccine was the nearest vaccine in sequence similarity to the local examined IBDV strains followed by CEVACIBDL then Bursine plus and Nobilis Gumboro indicating its probable success in the face of incoming outbreaks when using these vaccines. Phylogenetic analysis revealed that the presence of three clusters for the examined strains and are grouped with reference very virulent IBDVs of European and Asian origin (Japanese and Hong Kong) strains suggesting the different ancestors of our isolates. The antigenic index showed a number of changes on the major and minor hydrophilic antigenic peaks of the virus surface structures indicating a new genetic evolution of the surface structure epitopes that may lead to vaccination failure and reemergence of the disease.

Infectious bursal disease vaccine ameliorates velogenic Newcastle disease virus infection in immunopotentiated chickens

In the present study, the potential immunoprotective role of infectious bursal disease (IBD) vaccine on immunopotentiated chickens challenged with velogenic viscerotropic Newcastle disease virus (vvNDV) genotype VIId was investigated. The chickens were divided into five groups vaccinated with NDV vaccine, but group (G1) was kept as control unvaccinated birds. The G2 and G4 were immunopotentiated using mannan oligosaccharides (MOS) while G3 and G5 received MOS and IBD vaccine. The G1, G2, and G3 were infected with vvNDV while G4 and G5 served as uninfected birds. The humoral response to NDV vaccine was measured by hemagglutination inhibition test while cellular response was estimated by chicken interleukin-2 ELISA, total and differential leucocytic count, bursa body weight index, and histopathological examination of the bursae. The results revealed that the immunopotentiated groups possessed a good cellular and humoral response to vvNDV although the severity of histopathological lesions was variable. The G3 had the best cellular and humoral response, and IBD vaccine enhanced the immune response against the infection with vvNDV. Histopathologically, the typical bursal lesions of NDV were observed in G1 such as lymphocytic depletion, acute inflammatory reaction, and degenerative changes of the bursal follicles. In contrast, such histopathological changes in the immunopotentiated groups were less evident both in severity and prevalence, while the immune reactive lymphoid hyperplasia was a prominent finding in G4 and G5. In conclusion, the immunopotentiation of the chickens as well as NDV and IBD vaccination improved the bird immunity and diminished the immunosuppressive effect of the vvNDV.