A small-scale study on airborne transmission of H9N2 avian influenza virus under field conditions

Introduction: H9N2 avian influenza viruses (AIV) can transmit in chicken flocks through direct contact and aerosols. Nevertheless, data on airborne transmission of AIV is very limited, especially under field conditions. To fill this literature gap, this study was designed to investigate airborne transmission of H9N2 AIV originating from infected chicken flocks under field conditions, with the aim to further characterize the airborne transmission of H9N2 AIV. Methodology: Oropharyngeal swabs were collected from different diseased chickens to confirm H9N2 AIV infection. All glass impingers 30 (AGI-30) were used to collect indoor, upwind and downwind air samples for three chicken houses with H9N2 AIV infected chickens. Swabs and air samples were tested for H9N2 AIV using a real-time reverse transcription polymerase chain reaction (RRT-PCR). H9N2 AIV was isolated in embryonated chicken eggs and hemagglutinin (HA) gene sequence similarity of the isolated AIV was compared. Results: The results showed that indoor air samples were all RRT-PCR positive for H9N2 AIV. Downwind air samples collected between 10 m and 1.5 km away from the chicken houses were also found positive with an average load 2.62-5.21x10(3) RNA copies/m(3). However, upwind air samples were all negative for H9N2 AIV. In addition, H9N2 AIV was isolated from swabs and indoor air samples. Conclusion: In summary, this study provides insights into the airborne transmission of H9N2 AIV under field conditions.