Background and Aims: Newcastle disease (ND) is one of the most serious diseases among many species of birds and causes devastating effects on the poultry industry. This disease is endemic in Iran and ND outbreaks occur unexpectedly and with high mortality and severe clinical signs. The sequence of the F protein cleavage site is that the major virulence determinant of Newcastle disease virus (NDV). This study aimed to understand the molecular characterization of three NDVs isolates from commercial broilers from Qazvin province during 2019-2020. Thus, we can design appropriate control programs by obtaining useful data.
Materials and Methods: The partial open reading frame sequences of the F gene and haemagglutinin-neuraminidase (HN) genes of three isolates were amplified and sequenced. All sequences were edited using BioEdit Package and phylogenic trees were created based on the partial F gene sequences of isolates attained in this study and other NDV sequences available in GenBank with MEGA 7 software.
Results: The phylogenetic analysis displayed that the viruses belonged to genotype VII and further clustered into sub-genotype VII.1.1. Analysis of the F protein showed polybasic amino acid motif and a phenylalanine at position 117 at the cleavage site.
Conclusions: The similarity of these strains could indicate the entry of migratory birds from neighboring countries into Iran. Also, the role of backyard poultry is very important in the epidemiology of ND.  This study proclaims the urgency of effective control strategies.