Avian influenza virus (AIV) is prevalent in almost all countries with intensive poultry flocks. This disease mostly causes respiratory and gastrointestinal signs, but sometimes more complicated cases seen in commercial chickens. The aim of this study was to characterize the clinical aspects of A/chicken/Iran/m.1/2010 (H9N2) of AIV in infected SPF chickens. Forty two one-day-old SPF chicks were divided randomly into two groups (21chicks each group). At the age of 12 days old the chicks in group1 were inoculated intra-ocularly with 106EID50 of the H9N2 AIV, and the group2 was as control group. Chickens in each groups was evaluated from 2 to 14 days post inoculation. The results of this study indicated that the H9N2 subtype of AIV cannot cause mortality, and only slight clinical signs such depression, pneumonia were seen in infected chickens. These results demonstrated that H9N2 subtype was a low pathogenic and probably concurrent infectious in field situation causes severe clinical signs and high mortalities.
