الفهرس 
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Abstract
In Egypt recent outbreaks reported in NDV-vaccinated flocks and the isolated strain was characterized as velogenic NDV belong to class II genotype VIId. In this study, three inactivated NDV vaccine formulations have been prepared from LaSota (genotype II), genotype VIId NDV strain and combined lasota and genotype VIId of NDV at proportion of 1:1. In a challenge trial the prepared vaccines were evaluated in SPF chickens after challenge with 106 EID50/0.5ml velogenic genotype VII of NDV (NDV-B7-RLQP-CH-EG-12). Results revealed that the vaccines were able to achieve 100 % protection of vaccinated birds. The HI titers were statistically different in combined vaccinated group (Lasota and VIId NDV) compared to other groups. Employing VN test in the collected sera of vaccinated groups confirmed the HI and protection results. Studying of shedding pattern revealed that combined vaccinated group reduced the virus frequency and titer. Histopathological examination of collected organs after challenge indicated the protective effect in vaccinated groups compared to the severe lesion score shown in positive control group. In conclusion, the success of combined vaccine in inducing protection and reduction of shedding after challenge with recent genotype VIId of NDV.