Effectiveness of Market-Level Biosecurity at Reducing Exposure of Poultry and Humans to Avian Influenza: A Systematic Review and Meta-Analysis

The potential for these viruses to develop into a global influenza pandemic has prompted affected countries and the international community to mobilize funds for disease control. Live bird markets (LBMs) have been identified as potential hubs where AI viruses are maintained and transmitted for extended periods. Studies have documented that LBMs can serve as sources of human AI infections, with exposure to H7N9-infected poultry at these markets implicated as the main risk factor for human infection. In the context of animal health, biosecurity is the application of management practices that aim to reduce the risk of disease agent introduction and spread within and between animal populations. At LBMs, biosecurity practices can include introducing rest days, limiting the number of poultry species sold, using cleanable cages, and deploying adequate cleaning and disinfection procedures. A recent systematic review and meta-analysis evaluated risk factors for clinical outcomes in H5N1 patients, while another study quantified the role of farm-level biosecurity indicators in AI infection in poultry. However, the relative efficacy of different LBM biosecurity practices at reducing AI transmission to both humans and poultry in the LBM setting remains unclear. This study aimed to systematically review and meta-analyze the overall effect of different biosecurity indicators on AI infection from various studies to understand how each risk factor influences AI infection at market level and generate evidence to inform AI prevention and control programs at LBMs. A systematic literature search was conducted using PubMed, ISI Web of Science, Science Direct, CNKI, and WANFANG database, with no starting time limits, up to June 10, 2018. The search strategy used 4 PICO components, and epidemiological studies were included if they evaluated biosecurity risk factors for AI infection in LBMs in poultry, the environment, or human populations. A total of 34 biosecurity risk factors were explored in this study, including market characteristics, market biosecurity management, seasonality, temperature, sociodemographic characteristics, and activities involving exposure to poultry. Biosecurity measures effective at reducing AI market contamination and poultry infection at LBMs include smaller market size, selling single poultry species and separating different species, performing cleaning and disinfection, market closures, ban on overnight storage, and sourcing poultry from local areas. The meta-analysis indicates that higher risk of exposure to AI infection occurs in workers at retail LBMs, female workers, and those who contact ducks, conduct cleaning, slaughtering, defeathering, or evisceration. The most effective strategies to reduce AI market contamination identified in this study should target larger LBMs located at non-central city areas and selling and slaughtering multiple species of live poultry. Live bird market workers directly involved in cleaning and poultry processing tasks should participate in occupational health and safety programs. This information will allow national AI control program managers to make informed decisions on targeted risk-reduction strategies at LBMs and protect poultry, poultry workers, and consumers visiting these markets.