1Department of Veterinary Research and Biotechnology, Razi Vaccine and Serum Research Institute, Mashhad, Iran
2Department of Research and Diagnosis of Avian Diseases, Razi Vaccine and Serum Research Institute, Karadj, Iran
Sixteen avian influenza (AI) H9N2 viruses were isolated from disease outbreaks in different parts of Iran during (1998–2001). These AI isolates were used for pathogenicity, haemagglutinin (HA) gene variation and phylogenetic analysis. Results in both pathogenicity tests and HA gene cleavage site sequence detection represented a non-highly pathogenic feature for all Iranian AI isolates studied. The cleavage site motif (R-SS-R) of all AI isolates however, indicated that they had capability of becoming highly pathogenic viruses following 2 nucleotide substitutions at this region. Based on 450 nucleotides region obtained for local isolates and those for referenced viruses available in Gene Bank database used in phylogenetic analysis, all viruses placed on 3 distinct groups, 2 for Iranian and 1 for reference viruses. Among the reference AI viruses, isolates from Pakistan, Saudi Arabia and 1 from Germany showed less differences with Iranian AI isolates. Results also revealed that the circulating viruses in neighbouring provinces have been remained with less mutation for about 2 years.