Risk-based surveillance for avian influenza control along poultry market chains in South China: The value of social network analysis

Abstract

Over the past two decades, the poultry sector in China went through a phase of tremendous growth as well as rapid intensification and concentration. Highly pathogenic avian influenza virus (HPAIV) subtype H5N1 was first detected in 1996 in Guangdong province, South China and started spreading throughout Asia in early 2004. Since then, control of the disease in China has relied heavily on wide-scale preventive vaccination combined with movement control, quarantine and stamping out. This strategy has been successful in drastically reducing the number of outbreaks during the past 5years. However, HPAIV H5N1 is still circulating and is regularly isolated in traditional live bird markets (LBMs) where viral infection can persist, which represent a public health hazard for people visiting them. The use of social network analysis in combination with epidemiological surveillance in South China has identified areas where the success of current strategies for HPAI control in the poultry production sector may benefit from better knowledge of poultry trading patterns and the LBM network configuration as well as their capacity for maintaining HPAIV H5N1 infection. We produced a set of LBM network maps and estimated the associated risk of HPAIV H5N1 within LBMs and along poultry market chains, providing new insights into how live poultry trade and infection are intertwined. More specifically, our study provides evidence that several biosecurity factors such as daily cage cleaning, daily cage disinfection or manure processing contribute to a reduction in HPAIV H5N1 presence in LBMs. Of significant importance is that the results of our study also show the association between social network indicators and the presence of HPAIV H5N1 in specific network configurations such as the one represented by the counties of origin of the birds traded in LBMs. This new information could be used to develop more targeted and effective control interventions.

The role of live poultry movement and live bird market biosecurity in the epidemiology of influenza A (H7N9): A cross-sectional observational study in four eastern China provinces

“…The questionnaires had been used in previous studies by our team. 17,18 About 90% of live poultry are thought to come through wholesale markets on the way to retail markets. Some wholesale markets also sell live poultry directly to the consumer have been defined as mixed markets.…”

“…18 We summarised network connectivity using the number of links (indicating the frequency of movement), movement length (representing the catchment area of LBMs), degree centrality, k-core and the components of the network. The degree represents the absolute number of unique links of a given node; for example a degree of two means that the node (poultry market or source) is connected with two other unique markets or sources.…”

Interventions for avian influenza A (H5N1) risk management in live bird market networks

“…Previous studies in southeast Asia explored the flow of poultry through the Cambodian market chain (27), including the links between some LBMs and the supplying flocks in Vietnam (16) and China (28). However, the topology of the LBM contact network formed by the movements of poultry traders has not been assessed.…”

Risk analysis of H5N1 highly pathogenic avian influenza in poultry at the Poyang Lake area, China

“…A cross-sectional survey conducted in Cambodia found that all of the live poultry trade network establishes direct contact via live poultry traders in Thailand and Vietnam, and Phnom Penh is the hub of the live poultry trade (Van Kerkhove et al 2009). Another study found that taking measures in several hubs of a region by the way of disinfecting transport vehicles, equipment used for poultry, and the market environment everyday can greatly disconnect the virus' transmission network and effectively prevent the spread of the virus (Lockhart et al 2010;Martin et al 2011). Therefore, to understand the flow of live poultry better, investigations of the poultry trade network need to be carried out further in the Poyang lake area to explore its potential role in the process of introduction and transmission of HPAIV H5N1.…”

“…However, both environmental and anthropogenic factors were found to influence the risk of HPAIV H5N1 outbreaks in poultry at the village level (Fang et al 2008;. Both the density of roads and distance to the nearest roads have been shown to impact the possibility of HPAIV H5N1 occurrence, as roads act as major connections for trade and movement of infected poultry or products (Martin et al 2011;WHO 2011;Yupiana et al 2010). An analysis of demographic and environmental risk factors conducted in Indonesia proved that the most effective prevention measure is to interrupt contact between humans and poultry by restricting the breeding of live poultry in backyards and the live poultry trade (Yupiana et al 2010).…”