Background: In Egypt, outbreaks of Newcastle disease (ND) have been occurring in vaccinated chickens with great economic losses.
Objective: This work aimed for diagnosis and characterization of Newcastle Disease Virus (NDV) from infected broiler chickens in Egypt.
Methods: Suspected virus isolates on embryonated chicken eggs was detected by Hemagglutination (HA) test and identified using hemagglutination inhibition (HI) test. F protein encoding gene of NDV was amplified using Reverse Transcription-Polymerase Chain Reaction (RT-PCR) then subjected for nucleotide and amino acid sequence detection.
Results: NDV Giza 2014 isolate and NDV Qualubiya 2014 were characterized as velogenic and lentogenic strains, respectively using Mean Death Time (MDT), Intracerebral Pathogenicity Index (ICPI) and studying amino acid motif of the F protein cleavage site. Phylogeny put NDV Giza 2014 in a separate branch independent from other Egyptian isolates, however it is more related to Lasota (genotype II) and Clone 30 vaccinal strains, while NDV Qualubiya 2014 was grouped more related to Ulster strain (genotype I) and Australian isolates originating from the same ancestral node however it is distantly related to other Egyptian strains 2005 and 2006 grouped together with a common ancestral node but on a separate branch. These results proved diversity between the isolated velogenic NDV Giza 2014 strain and other vaccinal and circulating NDV strains.
Conclusion: It is concluded that further studies on the antigenic characters of that variant isolate is required to study antigenic variation between NDV strains circulating in Egypt.