Despite routine vaccination programs against Newcastle disease (ND), sporadic cases have occasionally occurred that remain a constant threat to commercial poultry. Egypt is endemic for Newcastle disease virus (NDV) with continuous long-lasting outbreaks causing significant losses in the poultry industry since 1948. This study was designed to identify various NDVs associated with outbreaks occurred in different localities in Egypt (El-Behera and Beni-Swief governorates) from March 2014 to November 2014among chicken flocks by RT-PCRand estimate its virulence in chickens byintra-cerebral pathogenicity index (ICPI). Thirty seven samples were collected from chickens either alive or dead showing characteristic clinical findings and post-mortem lesions of NDV. Virus propagation in embryonated chicken eggs was confirmed by hemagglutination (HA) test and identified by hemagglutination inhibition (HI) test using NDV specific antiserum. The results indicated that 16 (43.2 %) out of 37 samples were NDV positive. This results confirmed by RT-PCR which revealed that 16 out of 37 samples were NDV positive;13 samples were virulentNo. (3, 6, 7, 8, 9, 10, 11, 12, 15, 16, 23, 31, 34 & 37) and 2 were avirulentNo.(5, 32). By partial sequencing of the F protein cleavage site for the selected tenfield isolates from the sixteen positive isolates(No. 3, 6, 7, 8, 9, 10, 11, 12, 15 and 31)revealed thatthese isolates were velogenic type resembling the genotype 7 strain (NDV strain Chicken/China/SDWF07/2011).The ICPItest also revealed that theselectedten field isolates(No. 3, 6, 7, 8, 9, 10, 11, 12, 15 and 31) have a range from 1.55-1.79 index which congruent to velogenic type. These results confirmed that the circulating NDV strains are virulent for chickens.
