Evaluation of Two Inactivated Newcastle Disease Virus Vaccines (Genotype II and VII) Against Challenge of Newcastle Disease Genotype VII Infection in Chicken

摘要

Despite massive Newcastle Disease (ND) vaccination programs in Egypt several ND outbreaks were recorded since mid-2010 causing high mortalities (20-80%). The ND genotype VII Virus (vNDV) was the causative agent highlighting the need for evaluation of the efficacy of currently available and/or newly developed ND vaccines. In this study, the effectiveness of two inactivated NDV vaccines ?a virulent LaSota-like (NDV/CK/Egypt/11478AF/11) (genotype II) and vNDV, (NDV/CK/Egypt/567F/12) (genotype VII) strains were evaluated. The two NDV inactivated vaccines were prepred using 350 HAU/ dose and adjuvnated with Montanide ISA 70?. Post-Vaccination (PV) antibody response was monitored on weekly basis using Hemagglutination Inhibition (HI) test against both vaccinal antigens and the vaccine potency was tested at 4 weeks PV using 106 EID50/bird of vNDV (genotype VII) strain via oculonasal route. The vNDV inactivated vaccine induced significantly higher and earlier antibody titer than the LaSota-like strain inactivated vaccine by 2 weeks PV. The LaSota-like vaccinated birds showed mild clinical signs by 2 Days Post Challenge (DPC) and 20% mortality rate. In contrast, the vNDV vaccinated birds did not show any clinical signs or mortalities. Primarily, the vNDV strain vaccine reduced virus shedding compared to the LaSota-like strain vaccinated birds that showed virus replication with relatively high titers up to 6 DPC. In conclusion, superior protection against vNDV can be achieved using the closest vaccine seed to the circulating field isolates considering the induction of higher and earlier immune response, protection against morbidity and mortality and reduction of the challenge virus shedding.