The Protective Efficacy of Recombinant Herpesvirus of Turkey (rHVT-ND-IBD) Vaccine against Velogenic Newcastle Disease Virus Genotype VII.1.1.

Abstract

Newcastle disease virus (NDV) outbreaks have been reported worldwide invaccinated and non-vaccinated chicken farms, causing severe economic losses despiteextensive vaccination. This study assessed the effectiveness of recombinant herpes virus ofturkey (rHVT-ND-IBD) expressing the F protein of genotype VII with conventionalgenotype II vaccines against velogenic NDV genotype VII.1. 1. in broilers. Live ND vaccinewith inactivated vaccine (G1), live ND vaccine with rHVT-ND-IBD vector vaccine andinactivated vaccine (G2), live ND vaccine with rHVT-ND-IBD vector vaccine (G3) and LiveND vaccine alone (G4) were the four immunization programs that were employed. Alongwith the control non-vaccinated group (G5). Birds were challenged at day 28. Clinicalprotection, seroconversion, histological alterations, and viral shedding following challengewere used to evaluate protection. The results showed mild clinical signs in G2 and G3 thanin other groups, In addition, the mortality rates were 15%, 0%, 0% and 42.5% in G1, G2, G3and G4, respectively, vs 85% in G5. Moreover, the tracheal virus shedding in G2 and G3 wassignificantly (p ≤ 0.01) reduced when compared with G1, G4 and G5. The mean lesion score(MLS) was significantly (p ≤ 0.01) decreased in G2 and G3 compared to other groups. Theconclusion was that broilers immunized with rHVT-IBD-ND and NDV genotype IIvaccinations exhibited full clinical protection against NDV genotype VII.1.1. After that, it isadvised to give broilers rHVT-IBD-ND together with NDV genotype II vaccines to achievethe best possible clinical protection against genotype VII.1.1, particularly in endemicnations.