Abstract
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. 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. 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 2.62-5.21×103 RNA copies/m3. However, upwind air samples were all negative for H9N2 AIV. In addition, H9N2 AIV was isolated from swabs and indoor air samples. In summary, this study provides insights into the airborne transmission of H9N2 AIV under field conditions.
Highlights
H9N2 avian influenza viruses (AIV) can transmit in chicken flocks through direct contact and aerosols
H9N2 AIV belongs to the low pathogenic avian influenza (LPAI) virus, it increases morbidity and mortality rates when poultry are co-infected with other pathogens, such as Escherichia coli and Staphylococcus aureus [4,5]
In chicken farm A, 10 H9N2 AIV isolates were obtained from 7 swab samples (7/10, 70.0%) and 3 inside air samples (3/6, 50.0%)
Summary
H9N2 avian influenza viruses (AIV) can transmit in chicken flocks through direct contact and aerosols. Data on airborne transmission of AIV is very limited, especially under field conditions. 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. Results: The results showed that indoor air samples were all RRT-PCR positive for H9N2 AIV. H9N2 AIV was isolated from swabs and indoor air samples. In China, since H9N2 AIV was first isolated from diseased chickens in Guangdong Province in 1994, the virus has become the most prevalent type nationwide [6,7,8,9,10,11]. The wide prevalence of H9N2 AIV in poultry flocks, together with their ability to infect mammals, has raised concerns about their potential role in a possible influenza pandemic [14]. An in-depth understanding of the transmission characteristics of H9N2 AIV is of utmost importance
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