Studies on a recent IBD virus field variant isolate [electronic resource]: (3) immunogenicity of this variant strain compared with a classical strain in broiler chickens.

Includes references.

Three inactivated water-in-oil-in-water-emulsion infectious bursal disease virus (IBDV) vaccines were prepared from the Del/E related IBDV variant strain and a classical vvIBDV strain. Each IBDV strain were propagated for 6 serial passages in specific pathogen free (SPF) embryonated chicken eggs (ECE). The harvested IBD viruses were titrated in 10 day old ECE and inactivated using formalin at a final concentration of 0.2 % of the total volume. The fist vaccine contained Del/E related IBDV variant strain, the second vaccine contained vvIBDV strain and the third vaccine contained both variant and vvIBDV strain. The 3 prepared IBDV vaccines are evaluated compared to a commercial inactivated IBDV vaccine, all the 4 vaccines proved to be sterile and safe. The efficacy of each vaccine was assisted by inoculation into a group of 14 day old broiler chicks via subcutaneous rout and challenged (2 weeks later) with DellE related IBDV variant strain and the classical vvIBDV strain. The humeral immune response were determined using indirect ELISA, the geometric mean (GM) ELISA titer of the vaccinated chicken groups are significantly higher than the non vaccinated chickens, with no significant difference between the vaccinated chicken groups despite the variation in the IBDV strains. The protection was evaluated at 5 and 10 days post challenge, based on gross and microscopic lesions, bursal indices, proventricular/body weight ratio and bursl lesions scores. Vaccines made of variant IBDV alone or combined with vvIBDV protected chickens challenged with either the classical vvIBDV or the Del/E related IBDV variant strain while vaccines made of the classical IBDV strain alone protected chickens challenged with the classical vvIBDV strain but not against the DellE related IBDV variant strain.

Summary in Arabic.