Genetic analysis of H9N2 avian influenza viruses circulated in broiler flocks: a case study in Iraq in 2014-2015.

H9N2 avian influenza viruses (AIVs) have been recorded in Eurasian for several years. Since 2004-2005, the disease has become endemic in Iraq, causing serious economic losses in the poultry industry. The hemagglutinin (HA) and neuraminidase (NA), two out of eight protein-coding genes, play an important role during the early stage of infection and hinder virus assembling. Little is known about the genetic information of the H9N2 viruses currently circulating in Iraq; thus, gene sequences of six AIVS of the H9N2 subtype have been detected and analyzed in the period of 2014-2015 from different outbreaks of broiler flocks in five provinces situated in the middle and southern parts of Iraq. Genetic comparison of the partial sequences of HA gene indicated that all Iraqi viruses are related to each other and could be divided into two subgroups. Viruses of the first and the second subgroups demonstrated a high similar identity with Pakistani and Iranian viruses, respectively. The nucleotide sequences of the NA protein of the all studied Iraqi viruses were very similar (95.2-100% identity), and shared high nucleotide sequence identity with Iranian, Pakistani, and Lebanese strains. All six recent viruses possessed histidine, alanine, and leucine at positions 183, 190, and 226, respectively, which are the key residues in receptor-binding sites. The Iraqi viruses were closely related to viruses of G1-like lineage isolated from poultry flocks of Iran and Pakistan, suggesting that possible epidemiological links could be derived from a common origin. Further investigations are required and should include the viral isolation and full-length molecular characterization of H9N2 AIVs in this area.