الفهرس 
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Abstract
Newcastle disease (ND) is a highly contagious viral disease in domestic poultry, aviary and wild birds. Despite intensive vaccination programs, the virus remains a constant threat to the commercial poultry farms in Egypt as several outbreaks have occurred in Egypt since early 2011, in vaccinated and non-vaccinated poultry farms (Mohamed, 2012; Radwan et al., 2013; Hussien et al., 2014; Mostafa et al., 2014; Awad et al., 2015; Ewies et al., 2017 and saad et al., 2017) while the repeated outbreaks of virulent NDV among vaccinated chickens indicate the need to revise the NDV vaccination strategy.
we aimed through this work to evaluated the efficiency of vaccination with inactivated oil emulsion recombinant ND La Sota (Genotype VII ) or inactivated oil emulsion ND vaccine (Genotype II ) with or without live bivalent IB + ND vaccine and protectivity against challenge with velogenic Newcastle disease virus of genotype VII ”chicken/USC/Egypt/2014”.
200 broiler chicks were obtained from a commercial hatchery and divided into 5 groups in isolated and disinfected rooms. Four groups of 30 broiler chickens were vaccinated with different vaccination regimes of ND as chicks of group 1 were vaccinated with inactivated oil emulsion recombinant ND La Sota (Genotype VII ) at 7day and Live bivalent IB + ND vaccine at 7&15 days. Chicks of group 2 were vaccinated with inactivated oil emulsion ND vaccine (Genotype II) at 7day and Live bivalent IB + ND vaccine at 7&15 days. Chicks of group 3 were vaccinated only with inactivated oil emulsion recombinant ND La Sota (Genotype VII ). Chicks of group 4 were vaccinated only with inactivated oil emulsion ND (Genotype II) while broiler chickens of group 5 were kept as non vaccinated control group.
Blood samples from all birds were collected weekly at 1, 2, 3, 4 and 5 weeks of age in order to monitor the serological response using HI test. The obtained results revealed that the serological response of broiler chickens vaccinated with live ND vaccine and inactivated ND vaccine were higher – and thus provide more protection - than the serological response of broiler chickens vaccinated with inactivated ND vaccine only especially at 3,4 and 5 weeks of age.
Broiler chicks were challenged at 28th day of age with Velogenic Newcastle disease virus (Genotype VII) ”chicken/USC/Egypt/2014” and Results revealed that the non vaccinated group is badly affected ( showed severe nervous and/or respiratory signs) as well as sudden death where mortality rate 86.6%. On the other hand, broiler chickens vaccinated with both live and inactivated ND vaccines were protected against the challenge with velogenic virus where mortality was 0% while broiler chickens vaccinated only with inactivated oil emulsion recombinant ND La Sota (Genotype VII ) and broiler chickens vaccinated with inactivated oil emulsion ND vaccine (Genotype II ) showed moderate to severe respiratory and/or nervous signs where mortality was 40% and 46.6% respectively. These results agreed with all studies that confirm the integrative relationship between live and inactivated Newcastle disease vaccine in protection against ND.