Surveillance for avian influenza virus in external environment of live poultry markets in Shapingba district of Chongqing, 2017−2021

  Objective  To analyze the contamination of avian influenza virus in the external environment of live poultry markets in Shapingba district of Chongqing from 2017 to 2021.

  Methods  A total of 1200 environmental samples of 6 kinds, including stool samples (anal swabs) , cage surface swabs, chopping board surface swabs, knife surface swabs, container and washing water samples, were randomly collected from 21 live poultry markets in Shapingba for the detection of influenza A virus by real-time polymerase chain reaction (RT-PCR). Positive samples were further tested for H5, H7, H9 and N9 subtypes by sequencing. Statistical analysis was conducted by using SAS 8.2.

  Results  The overall positive rate of influenza A virus was 68.50%, and the positive rates of subtype H5, H7, H9, N9 and unspecific subtype were 26.33%, 0.17%, 45.50%, 0.00% and 17.17%, respectively, the differences were significant (χ²=315.563, P<0.001). The co-detection rates of H5+H9, H7+H9 and H5+H9+N9 were19.83%, 0.67% and 0.67% respectively. The differences in annual positive rate of influenza A virus were significant (χ²=296.199, P<0.001). The differences in seasonal positive rate of influenza A virus were significant (χ²=35.350, P<0.001). The positive rate of influenza A virus was highest in the first quarter (79.17%), followed by the second quarter (76.76%). There were no significant differences in the positive rate of nucleic acid of influenza A virus among the samples collected from different markets (χ²=11.062, P=0.087). Among the different types of samples, the positive rate in swabs of chopping board surfaces was72.00%, and the positive rate in swabs of knife surfaces was 71.00%. There were no significant differences in the positive rate of influenza A virus nucleic acid among the 6 types of samples (χ²=6.813, P=0.235).

  Conclusion  Avian influenza virus contamination was common in the external environment of live poultry markets in Shapingba, especially in the first and second quarters of the year, the predominant subtype was H9. Co-infection of subtypes accounted for a certain proportion. Close attention should be paid to the emergence of novel reassortants and variants of avian influenza virus, such as H9N9 and H5H9, etc. It is necessary to strengthen the supervision and management of live poultry markets and conduct regular disinfection in the markets.