The Molecular detection and pathotypic characterization of Genotype VII.2 of Newcastle Disease Virus Isolated from Imported Cockatiels in Iran

Abstract

Genotype VII of Newcastle disease virus (NDV), the most prevalent genotype of avian paramyxovirus I (APMV-1) in Asia, is rapidly spreading worldwide. The emergence of new sub-genotype VII.2 in different countries raises questions about the evolutionary patterns of these isolates. Despite the devastating effects of NDV on endangered parrot species and the major role of the psittacines in the cross-species transmission of the virus, there have not been any phylogenetic studies on the NDVs circulation in these populations in Iran. In this regard, a brain sample obtained from three dead cockatiels of a suspected NDV flock with an 80% mortality rate was implemented for further molecular, pathogenicity, and phylogenetic analysis of the fusion gene and deduced amino acid sequences. Pathogenicity indices and Cleavage site investigation revealed the high virulence (¹¹²RRQKRF¹¹⁷) of the virus. Phylogenetic studies clustered our isolate (SR0077) among VII.2 sequences from Pakistan, Indonesia, China, Jordan, and Malaysia. Moreover, the nucleotide distances between the studied isolate and VII.2 strains reported from Pakistan were less than 0.01. However, non-VII.2 isolates previously reported from Iran were phylogenetically distinct from our isolate. Taken together, these findings, along with some identical substitutions at functional domains of the F protein, highlight the risk of introducing VII.2 strains to other countries and the possible incidence of new panzootics.  Finally, based on history and molecular analyses, it seems that bird trade from Pakistan is the main cause of the development of new VII.2 NDV strains in Iran.