Social network analysis of the movement of poultry to and from live bird markets in Bali and Lombok Indonesia

Highly pathogenic avian influenza H5N1 has resulted in large losses to the Indonesian poultry sector. Evidence suggests that live bird markets (LBMs) play an important role in epidemiology of the disease. Knowledge of the frequency and type of contact between the various poultry market players should allow animal health authorities to develop a better understanding of factors influencing virus transmission between Indonesian villages. A questionnaire-based cross sectional survey was conducted in 17 LBMs on the neighboring Indonesian islands of Bali and Lombok to investigate the movement patterns of poultry to and from markets. Using social network analyses, a network of contacts was created of each island from a total 413 live poultry traders and 134 customers. Individual nodes with high degrees and/or betweenness were indentified in each network. The Lombok network as more dense and connected than the Bali network indicating that disease transmission would be more efficient in the Lombok network. Our findings indicate that whilst live poultry are typically transported over relatively short distances of approximately 10 km, it is uncommon for traders and customers to travel in excess of 100 km to buy and sell poultry, which may facilitate the spread of disease over a large geographical area. This study highlights the different roles markets in poultry movement networks and their potential for disease dissemination. The identification of highly influential market nodes allows authorities to target HPAI surveillance activities to locations where disease is more likely to be present, which is crucial in low-resource setting. Keywords: H5N1, highly pathogenic avian influenza, Indonesia, live bird markets, social network analysis