Patterns of contact within the New Zealand poultry industry.

Members of the Poultry Industry Association and the Egg Producers Federation of New Zealand (n=420) were sent a questionnaire asking them to describe the type and frequency of on- and off-enterprise movements relating to feed, live birds and hatching eggs, table eggs and poultry product, and manure and waste litter. Social network analyses were used to describe patterns of contact among poultry enterprises and their associates for these four movement types. The response rate to the survey was 58% (244 out of 420). Network structures for enterprise-to-enterprise movements of feed, live birds and hatching eggs, and table egg and poultry product were characterised by 'hub and spoke' type structures with small-world characteristics. Small worlds were created by network hubs (e.g. feed suppliers and hatcheries) providing goods and services to larger numbers of client farms. In addition to hubs acting as the predominant source of material moving onto farms we identified enterprises acting as bridges between identified small worlds. The presence of these bridges is a concern, since their presence has the potential to facilitate the spread of hazards (e.g. feed contaminants, infectious agents carried within feed) more readily throughout the population. An ability to predict enterprises with these network characteristics on the basis of factors such as shed capacity, enterprise type, geographic location would be useful for developing risk-based approaches to disease prevention, surveillance, detection, response and control activities.