Genetic analysis of avian paramyxovirus type I strains isolated from backyard poultry in Iran.

Newcastle disease (ND) is one of the most serious diseases amongst many species of birds and causes huge economic losses in the poultry sector. Backyard poultry are the main source of food in rural areas of many developing countries and play a crucial role in the epidemiology of ND. The sequence of the F protein cleavage site is the major virulence determinant of Newcastle disease virus (NDV). The aim of this study was to understand the molecular characterization of F proteins of Iranian backyard poultry in NDVs. The complete open reading frame sequences of the F gene of six isolates were amplified and sequenced. All characterized NDVs had high similarities to Chinese isolates. The phylogenetic analysis revealed that the studied strains fell into genotype VII and grouped in a specific subgenotype. All tested NDVs have a cleavage site of 112RRQKR↓F117, representing that all of them belonged to velogenic strains. Rearing methods of backyard poultry increase the chance of contact between a variety of poultry and wild birds; subsequently, new strains evolve and are transmitted between them. Therefore, continuous monitoring of NDVs in backyard poultry would help us to obtain more information about the evolution of NDVs and improve new control strategies in backyard poultry. [ABSTRACT FROM AUTHOR]