الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Newcastle Disease (ND) has maintained its status as one of the most significant and lethal viral diseases affecting poultry globally. This impact is particularly pronounced in developing countries.
Twenty-three tracheal samples were collected from vaccinated broiler, layer and breeder flocks suffered from respiratory, nervous symptoms and DROP in egg production between October 2019 and December 2020.
Only ten samples (10/23; 43.5%) showed HA activity after propagation into ECE while only six samples were positive for avian avulavirus 1 based on real time RT-PCR.
Nucleotide sequences for both F and HN genes showed high similarity to recently reported Egyptian NDV isolates.
Sequencing for the F protein cleavage site showed the typical sequence of velogenic NDV strains (112R-R/K-Q-K-R↓F117).Deduced amino acid analyses for F and HN proteins genes showed different substitutions in comparison with the commonly used vaccine strains.