ORIGINAL ARTICLE Social Network Analysis for Assessment of Avian Influenza Spread and Trading Patterns of Backyard Chickens in Nakhon Pathom, Suphan Buri and Ratchaburi, Thailand C. Poolkhet 1,2 , P. Chairatanayuth 3 , S. Thongratsakul 2 , N. Yatbantoong 2 , S. Kasemsuwan 2 , D. Damchoey 4 and T. Rukkwamsuk 2 1 Tropical Agriculture Program, Graduated School, Kasetsart University, Bangkok, Thailand 2 Faculty of Veterinary Medicine, Kasetsart University, Nakhon Pathom, Thailand 3 Faculty of Agriculture, Kasetsart University, Bangkok, Thailand 4 King Mongkut’s Institute of Technology Ladkrabang at Chumpon, Chumpon, Thailand Impacts • Important nodes in the spread of avian influenza are farmers who raise chickens for consumption only, farmers who raise chickens for consump- tion and fighting cocks, neighbours with backyard poultry, and the owners and observers of fighting cocks at arenas and training fields. • The key players must be controlled to achieve the goal of disease control. • The backyard chicken network has low density and a low clustering coefficient, which means that the network has a random pattern. Introduction The highly pathogenic avian influenza (HPAI) subtype H5N1 in poultry is a zoonotic disease in human beings. The virus can infect a wide variety of avian species and mammals, affecting both the poultry industry and human health. In the past, outbreaks of avian influenza occurred throughout the world. During 2011, the disease spread to Keywords: Social network analysis; avian influenza; backyard chicken; Thailand Correspondence: C. Poolkhet. Department of Veterinary Public Health, Faculty of Veterinary Medicine, Kasetsart University, 1 Moo 6, Malaiman Road, Kamphaeng Saen, Nakhon Pathom 73140, Thailand. Tel.: +66 865 580 441; Fax: +66 343 514 05; E-mail: fvetctp@ku.ac.th Received for publication March 22, 2012 doi: 10.1111/zph.12022 Summary The aim of this study is to explain the social networks of the backyard chicken in Ratchaburi, Suphan Buri and Nakhon Pathom Provinces. In this study, we designed the nodes as groups of persons or places involved in activities relating to backyard chickens. The ties are all activities related to the nodes. The study applied a partial network approach to assess the spreading pattern of avian influenza. From 557 questionnaires collected from the nodes, the researchers found that the degree (the numbers of ties that a node has) and closeness (the distance from one node to the others) centralities of Nakhon Pathom were sig- nificantly higher than those of the others (P < 0.001). The results show that compared with the remaining areas, this area is more quickly connected to many links. If the avian influenza virus subtype H5N1 was released into the network, the disease would spread throughout this province more rapidly than in Ratchaburi and Suphan Buri. The betweenness centrality in each of these provinces showed no differences (P > 0.05). In this study, the nodes that play an important role in all networks are farmers who raise consumable chicken, farmers who raise both consumable chicken and fighting cocks, farmers’ house- holds that connect with dominant nodes, and the owners and observers of fighting cocks at arenas and training fields. In this study, we did not find cut points or blocks in the network. Moreover, we detected a random network in all provinces. Thus, connectivity between the nodes covers long or short dis- tances, with less predictable behaviour. Finally, this study suggests that activities between the important nodes must receive special attention for disease control during future disease outbreaks. Zoonoses and Public Health 448 ª 2012 Blackwell Verlag GmbH Zoonoses and Public Health, 2013, 60, 448–455