Efficacy of the Genotype-Matched and Non-Matched Vaccines Against Newcastle Disease ‎Virus Genotype VII.1.1. Challenge in Broiler Chickens

Abstract

Despite extensive vaccinations attempts, genotype VII Newcastle disease viruses (NDV) continue to circulate at the Middle East and Asia causing significant economic losses. In this investigation, we assessed the effectiveness of three inactivated NDV vaccines; genotype II NDV, recombinant genotype VII NDV-matched and laboratory prepared autogenous velogenic NDV genotype VII against challenge by genotype VII velogenic NDV. The following vaccinations were given: group 1(G1) received an inactivated genotype II vaccine, group 2 (G2) received an inactivated recombinant genotype VII NDV-matched vaccine, and group3 (G3) received a velogenic inactivated autogenous NDV genotype VII vaccine. While the live genotype II (Lasota) vaccine was administered to all groups. At the age of 28 days, birds in all vaccination groups were challenged with NDV genotype VII, and protection against infection was assessed based on the mortality number, clinical symptoms, Post mortem lesions, virus shedding, and histological changes. The results of clinical protection were78%, 87% and 96% in vaccinated groups G1, G2 and G3 respectively, against 7 % in the control non-vaccinated challenged group. Virus shedding in all vaccinated groups significantly reduced when compared to the nonvaccinated group (G4). The mean lesion score on 4 and 7 days post challenge were significantly reduced in G3 and G2 compared to G1.In conclusion, more protection against challenge was offered by a velogenic inactivated autogenous NDV genotype VII vaccine that was closely related to genotype VII.1.1 strain than by other vaccines. So we recommended the use of genotype matched vaccine to control NDV in endemic countries.