Poultry trading behaviours in Vietnamese live bird markets as risk factors for avian influenza infection in chickens

Sealy, Joshua E.; Fournie, Guillaume; Trang, Pham Hong; Dang, Nguyen Hoang; Sadeyen, Jean-Remy; Thanh, To Long; van Doorn, H. Rogier; Bryant, Juliet E.; Iqbal, Munir

systems, often without robust biosecurity (Fournié et al., 2016; Webster, 2004) . Live bird markets (LBMs) are a traditional aspect of these systems that facilitate the storage and sale of live poultry including chickens, ducks, quail and pigeons. As a consequence, LBMs play a significant role in the maintenance and spread of AIVs and thus pose a zoonotic risk to poultry workers and consumers, and to temporary workers enlisted during stamping out programmes (Bridges et al., 2002; Mounts et al., 1999) . LBMs have been a primary target for AIV control strategies; during a zoonotic outbreak of H7N9 in China in 2013, closure of LBMs was shown to be remarkably effective in reducing the risk of human infection by up to 99% (Yu et al., 2014) . Control strategies in LBMs have also been shown to significantly reduce AIV detection in chickens: the most effective strategies include monthly rest days that involve routine market closure followed by slaughter of unsold poultry, a ban to the sale of live quail and a ban to overnight storage of live poultry (Kung et al., 2003; Lau et al., 2007; Leung et al., 2012) . However, although rest days are effective at breaking the viral amplification cycle in LBMs, they do not prevent reintroduction of virus. Indeed, rest days/nights are an important component of long-term AIV control but are not sufficient alone to eliminate infection (Kung et al., 2003) . Furthermore, risk factor studies in LBMs have shown that having a greater variety of poultry species, including ducks being sold alongside other species, having poor sanitary conditions, storing poultry in floor pens instead of cages and having ≥1 wholesaler trading in LBMs, all increase the odds of having AIV-infected poultry and/or having AIV-contaminated environments (Kim et al., 2018; Kirunda et al., 2015; Santhia et al., 2009; Sayeed et al., 2017; Wang et al., 2018) .