Characterization of the avian influenza viruses distribution in the environment of live poultry market in China, 2019-2023.

Abstract

Background: The prevalence and transmission of avian influenza viruses (AIVs) in the live poultry market (LPM) is a serious public health concern. This study was to investigate the prevalence of different subtypes of avian influenza viruses in environment of LPM, and to analyze the differences and seasonality of the nucleic acid positive rate (NAPR) of A type, H5, H7, and H9 subtypes in feces, sewage, drinking water, breeding cages, and chopping boards.

Methods: Feces, breeding cages swabs, drinking water, sewage and chopping boards swabs were collected from live poultry market during 2019-2023 from southern and northern China. Real-time PCR was used to screen for virus subtypes. Viruses were isolated, and deep sequencing was performed to obtain whole-genome sequences. Chi-square test was used for statistical analysis of categorical variable, GraphPad Prism software were used to construct graphs.

Results: A total of 64,599 environmental samples were collected from live poultry markets in the southern China and northern China between 2019 and 2023. The average NAPR of the A type was significantly higher in the samples collected from the southern China than in those collected from the northern China (P < 0.05). The NAPR of H5, H7, and H9 subtypes carried by the five types of environmental samples in the southern China were significantly different (P < 0.05), and a higher NAPR was detected in chopping boards (10.84%), breeding cages (0.28%), and drinking water (40.97%) respectively. The average NAPR of the H9 and H5 subtypes displayed seasonality, reaching a peak in January and February in the southern China, while the peak of the H9 subtype was from October to February in the northern China. A total of 19 subtypes were identified. The H5 subtype significantly decreased, the H7 subtype was almost undetectable, and other subtypes, such as the H3 subtype, increased.

Conclusions: The highly pathogenic H5 subtype has significantly decreased in the live poultry market in China since 2022. However, the proportion of some subtypes, such as the H3 subtype, with low pathogenicity to poultry, has increased, while the H9 subtype remains at a high level. It must be noted that these low pathogenic avian influenza viruses often have no obvious symptoms, can circulate asymptomatically in infected poultry, and are highly pathogenic to humans. Our findings provide insights into the control and prevention of avian influenza viruses and the risk of pandemics associated with avian influenza viruses in the live poultry market.