Efficacy of Commercial (HVT-ND) Vector Vaccine Against Newcastle Disease Virus Genotype ‎VII.1.1 Challenge in Commercial Broiler Chickens

Genotype VII Newcastle disease viruses (NDV) are still circulating in Egypt despite extensive vaccination programs. In our study, we evaluate the protective efficacy of commercial (HVT- ND) vector vaccine against velogenic NDV Genotype VII.1.1 challenge in broiler chickens. Five vaccination strategies  were established; G1 vaccinated by HVT-ND vaccine, G2 vaccinated by HVT-ND and 2 live ND vaccines, G3 vaccinated by HVT-ND, inactivated ND and 2 live ND vaccines, G4 vaccinated by 2 live ND vaccines, G5 vaccinated by inactivated ND and 2 live ND vaccines and G6 Non-vaccinated challenged. All birds were challenged atthe age of 28 days-old. The protection evaluation based on mortality, clinical symptoms, gross pathological lesions, immune response and the mean lesion scores (MLS) of histopathological lesions in brain and trachea at 14 days post challenge. Our findings showed that mortality rates were 26.6 %, 16.6%, 30% and 3.3%, respectively, in G1, G2, G4 and G5, while the best protection was in G3 that did not show any mortality versus 93.3 % in G6. Moreover the MLS on 7dpc were 1.75, 1.6, 1.18, 1.65 and 1.23, in G1, G2, G3, G4 and G5, respectively, while it reached to 2.5 in G6. Results of virus shedding in all vaccinated groups significantly reduced while (G3) also show the more reduction of virus shedding. It could be concluded that full clinical protection against challenge with genotype VII.1.1. NDV can be achieved by co-administrating of HVT-ND, inactivated ND and live ND vaccines as a vaccination program in endemic regions.