Abstract:

Objective To understand the distribution of avian influenza viruses in the external environment of Anhui Province and the antibody levels of occupational exposure populations for scientific evidence for controlling avian influenza outbreaks. Methods According to the avian influenza-related monitoring plan, we collected environmental pathogen detection of avian influenza and serological surveys on occupationally exposed groups in Anhui Province during 2022 and 2024. All samples from urban and rural live poultry markets, large-scale poultry farms, concentrated areas of poultry free-range farmers, poultry slaughterhouses and processing plants, and wild bird habitats. Real-time fluorescent quantitative PCR was applied to detect the nucleic acid of avian influenza A virus in the samples, and positive specimens were further tested for H5, H7, and H9 subtypes. Antibody monitoring was conducted for the occupational populations exposed to avian influenza Hefei, Ma’anshan, Fuyang, and Chizhou. Descriptive epidemiological methods were used to statistically analyze the monitoring results in the four cities. Results From 2022 to 2024, a total of 3 919 environmental samples for avian influenza were obtained in Anhui Province, with 1 455 samples tested positive for influenza A virus nucleic acid, and a positive rate of 37.13%. The positive samples were mainly of the H9 subtype (1 158 specimens, 79.59%), and there were mixed positive specimens of H5+H9 and H7+H9. The positive rate was relatively high from July to September and from November to January of following year(42.49%，41.03%). Among the monitoring sites, the positive rate was the highest in poultry slaughterhouses and processing plants (52.27%). Of the samples, the positive rate of wastewater from poultry cleaning was the highest (46.36%), and the difference was significant in the positive rates among different sites and specimen types (χ²=283.922, 76.204; both P<0.001). A total of 1 025 aliquots of serum samples were obtained from the occupational exposure populations, in which positive findings were seen in 70 samples, with a positive rate of 6.83%. In the single subtypes, H5N6 positive accounted for the highest proportion (52.86%, 37/70). Among all cities, the highest antibody positive rate was seen in occupational exposure populations in Hefei (10.19%). Among various sites, the concentrated areas of poultry free-range farmers (9.86%), with H5N6 and H10N3 antibody positive samples all from the concentrated areas of poultry free-range farmers. Conclusion There are multiple subtypes of avian influenza viruses in the external environment of Anhui Province, with the H9 subtype being the main one. H5N6 subtype is more seen in the occupationally exposed populations with positive serum antibodies. It is recommended to focus on strengthening the supervision of high-risk sites like urban and rural live poultry markets, conducting avian influenza prevention and control publicity for poultry free-range farmers, and continuously implementing avian influenza monitoring to reduce the risk of human infection with highly pathogenic strains like H5N6.

Key words: Avian influenza virus, External environment, Occupational exposure population, Anhui Province