الفهرس 
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Abstract
Abstract
Infectious bursal disease control has focused mainly on the vaccination program, which provides protection against mortality and immunesuppression. Comparing the protective efficacy of herpes virus of turkey-infectious bursal disease(HVT-IBD) vector vaccine in-ovo using commercial in-ovo machine (Ovo-Jector) and post-hatch vaccination against Egyptian very virulent infectious bursal disease (vvIBDV) isolate ”Lay./Men.Egypt/017” (GenBank accession no. MN 823616) was evaluated in broiler chicks. The protection assessments were evaluated after experimental infection, on days 21or28, based on clinical signs, mortality rates, bursa/body weight ratio (B/BWR), gross lesions, the mean severity index (MSI) of histopathologic lesion scores and serological response to IBDV vaccination at 7-days post-challenge(DPC). As results, the two vaccination regimes protected 100% and100% vs90% and 100% of chickens against mortality.
when challenged on the 21th and the 28th days of age, in-ovo vs. post-hatch vaccination compared with 90% and 80% in non-vaccinated challenged chickens, respectively. In addition, the B/BWR of in-ovo and post-hatch vaccination regimes was 1.17;0.93 and 0.98;0.90 vs 0.65and0.50 in non-vaccinated challenged chickens on days 21 or 28, respectively. A significant difference of the MSI was shown, 1.0;1.5 and1.8; 2.5when challenged on the 21th and the 28th days of age, in-ovo and post-hatch vaccination vs 3.0 and 3.5 in non-vaccinated challenged chickens, respectively. Our results revealed that the in-ovo vaccination of HVT-IBD vector vaccine is providing early onset of protection against the Egyptian vvIBDV in broilers and could safely replace the current post-hatch vaccination practices.