Efficacy of The Turkey Herpes virus-IBDV Vector Vaccine Against Recent Egyptian Very Virulent IBDV in Commercial Layers

Abstract

The infectious bursal disease virus (IBDv) is widespread in poultry flocks all around the world. During the period between 2016- 2017, 22 IBD outbreaks were investigated in El-Minoufiya Governorate in different chicken sectors (11 broilers, 7 commercial layer pullets and 4 native baladi varieties). The disease occurred at 23-42 days of age. The mortality ranged between 3-9 % in commercial broilers farms, 5.8-12% in native breed varieties and 5-10 % in commercial layer replacement pullets. Two hundred one-day-old commercial male layer chicks was used for assessment of protection obtained after vaccination with HVT-IBDV vector vaccine Vaxxitek against challenged with vvIBDV local field isolate Lay./Men.Egypt/17 at 46th-day of age. Maternal derived antibodies (MDA) was followed up by ELISA to determine MA waning and the suitable age of chicks for IBDV vaccination and/or challenge. Chicks divided into 4 groups of (50 birds/ of each), G1 (vaccinated with HVT-IBD vector vaccine at 1 day old of age and non-challeneged) and G2 (vaccinated with HVT-IBDV at one-day of age and challenged with vvIBDV local field isolate Lay./Men.Egypt/017 at 46-day of age), G3 (non- vac-cinated and non-challenged) and G4 (non-vaccinated and challenged chickens). Our results revealed that the mortality percentage of commercial male layer chickens chal-lenged with recent vvIBDV local field isolate lay./Men.Egypt/017 was (0%) in G2, while in G4 was (90%), at 7-days post challenge. The highest bursa body ratio observed was (5.32 and 5.31) in non- vaccinated and non-challenged birds (G3) and birds vac-cinated with the VAXXITEK HVT-IBDv vaccine (G1). Conclusion, the recombinant VAXXITEK HVT-IBDv vaccine has provided protection for commercial male layer chicks against challenge with recent vvIBDv isolate. Vaccination with vector vaccine in en-demic areas with vvIBDV, protect against mortality, partially against bursal atrophy and decreases immunosuppressive effect of vvIBDV.