Abstract
In the present study, fifty broiler chickens flocks suspected to be infected with Newcastle disease virus (NDv) in 5 Egyptian provinces Gharbia (7/50), El Behera(21/50), Kafr EL sheikh (8/50) and Matrouh(7/50) and Alexendaria(7/50) during the period (from september 2015 to February 2017) were investigated for clinical and postmortem examination as well as virus isolation and molecular identification. The results of virus isolation on embryonated chicken SPF eggs (ECE) revealed that 16/50 samples were haemagglutinatig agents by slide haemagglutination test.These haemagglutinating agents were confirmed as NDv by real time PCR .The deduced amino acid sequences of the fusion protein of selected 8 positive isolates revealed that (7/8) isolates possessed the motif 112RRQKRI117at the cleavage site,indicating that these isolates are velogenic ,whereas the other (1/8) isolates carries the motif 112GRQGRL117indicating that is lentogenic . Phylogenetic analysis demonstrated that the 7 strains belong to the NDv genotype VIId, and the other strain was of genotype II.These isolates were detected even in vaccinated flocks that indicate the possible causes of those outbreaks may be not only useless of vaccines ,but also immunesuppression,use of heterogenous vaccines ,improper application of biosecurity ,moreover,may be arole in spreading of velogenic strain of NDv in Egypt .
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