Avian influenza virus in various environments and risk factors for the contamination of live poultry markets during winter and spring season in Zhejiang province

Abstract

To evaluate the prevalence of avian influenza virus in various environment and the influence factors for subtype H7 prevalence in live poultry markets. We collected environmental samples from various environments across 11 cities of Zhejiang province between October 2014 and March 2015. Cage surface swabs, chopping board surface swabs, feces, water for cleaning, drinking water and swabs of other surfaces were collected. A total of 6 457 samples were collected, including 4 487 samples from poultry markets, 820 samples from poultry farms, 715 samples from backyard poultry pens, 118 samples from poultry processing factories, 118 samples from wild bird habitats and 86 samples from other sites. The chi-squared test was used to compare virus prevalence among sample types, sites types, and poultry markets types. Binary logistic regression was used to analyze factors on H7 subtype prevalence in poultry markets. Of 6 457 samples, 32.54% (2 101) samples were positive for avian influenza, with 3.67% (237) positive for H5 subtype, 12.02%(776) positive for H7 subtype, 11.77%(760) positive for H9 subtype. Of 237 live poultry markets, 33.8% (80) were positive for H7 subtype. The prevalence of influenza A in poultry processing factories was the highest at 43.72% (101/231) (χ(2)=737.80, P<0.001). Poultry markets were contaminated most seriously by subtype H5/H7/H9 with the prevalence of 27.55% (1 236/4 487) (χ(2)=436.37, P<0.001). Compared with markets with 1 type of poultry, OR was 4.58 (95%CI: 1.63-12.87) for markets with ≥2 types of poultry. Live poultry markets and poultry processing factories were contaminated most seriously by avian influenza. The types of poultry might be the factor which influenced the subtype H7 prevalence in poultry markets.