الفهرس 
Studies on genotype VII of newcastle disease virus infection in chickens
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Abstract
Seventy nine chicken flocks were investigated for the presence of NDV using RT-PCR F- protein gene assay using degenerate primers specific for velogenic strains of NDV, 23 flocks tested positive for vNDV. Four representative isolates were sent for partial sequencing of the F- protein gene. Results revealed that all isolates have multiple basic A.A at the F- protein cleavage site possessing the velogenic motif (¹¹².RRQKR*F.¹¹⁷). Phylogenetic analysis of the F- protein 375 b.p. hyper variable region (nt 47-422), revealed that all isolates are belonging to genotype VIId with (98%-99%) amino acid identity matrix with the Israelian 2 (Turkey-Israel-111-2011) and chinese 2 (chicken-china-SDYT03-2011) strain, genotype vIId. Single pure NDV isolated strain was selected (NDV/chicken/EG-QU/NRC/2015, acc. No. MF418018) after testing negative for AI (H5, H9), IB virus. Titration of the selected strain reveals MDT of (36 hr.) and 10 EID50/ 0.1 ml. In vivo vaccination protection study was done using 7.7 different vaccination programs for protection against challenge with the locally isolated (NDV/chicken/EG-QU/NRC/2015, acc. No. MF418018).Commercial broiler chicks were divided in to 7 different vaccination groups including positive non-vaccinated control group. Results revealed that group vaccinated with La sota with inactivated NDV vaccine showed 100% protection rate against mortality and emergency vaccination after challenge using La sota vaccine gave the best result