Spatial risk assessment of the zoonotic influenza A (H7N9) along the live meat chicken market chain in Southeast China

Abstract

Introduction:A new reassortant avian influenza A (H7N9) virus of low pathogenicity to poultry emerged in eastern provinces of China in early 2013. There have been five epidemic waves causing more than 1600 human infections in 29 provinces and municipalities in mainland China till May 2018.Exposure to H7N9 infected live meat chickens at live bird markets (LBMs) within the affected provinces was suggested to be the main risk factor for human infection. Previous studies demonstrated the role of poor biosecurity measures at poultry farms and LBMs and the role of live poultry trade in the dissemination of avian influenza (AI) virus. However, the continued and increasing number of reported human H7N9 cases throughout China indicated that vulnerabilities linked to the live meat chicken market chain remain, that need to be elucidated in order to better design surveillance programmes and health promotion interventions to prevent poultry and human exposure along the live meat chicken market chain. Aims:The overall aim of the research in this thesis is to define the risks of sustained transmission of H7N9 virus along the live meat chicken market chain in eastern China. To meet the aim, studies were sequentially designed with the following specific objectives: 1) identify the effect of market-level risk factors on avian influenza infections in poultry and humans and generate evidence that will inform avian influenza prevention and control programs at LBMs; 2) to understand the role of live poultry movement and live bird market biosecurity in the epidemiology of H7N9 during the emergency; 3) to understand the level of knowledge, attitudes and practices (KAP) on avian influenza of different actors along the live meat chicken market chain and the risk factors associated with their KAP levels; 4) to develop a spatial risk assessment model of the live chicken market chain within the H7N9 high risk area, to provide essential evidence and recommendations for risk-based AI surveillance programs and appropriate enhancements to current prevention and control policies for H7N9 in the study area. Methods:To address each of the specific objectives four studies have been designed. Firstly, we performed a systematic literature review and estimated the pooled odds ratios of biosecurity indicators relating to human and poultry AI infections at market level using a quality effects meta-analysis model. Secondly, we identified the biosecurity risk factors associated with the H7N9 presence in the surveyed LBMs in the affected provinces during the H7N9 emergency response. We also used social network analysis and spatial analysis to quantify the connectivity of counties in Eastern china via live poultry movements and identify highly connected areas associated with human cases. Then, to quantify differences in KAP of AI among different actors (chicken farmers, live chicken vendors and consumers at LBMs) along the live chicken market chain operating within the areas in the Eastern provinces (i.e.ii Shanghai, Jiangsu, and Anhui) identified in the pre...