Abstract
Most preventative and countermeasure tactics aimed at controlling between-premises disease spread in livestock systems rely on identifying and restricting animal movement. Therefore, it is essential to uncover between-premise movement dynamics, including nationwide network profiles and distances to which animals are transported, to develop network-based control strategies. Currently, within-state animal movements in the U.S. are not regulated, making it difficult to acquire accurate data necessary to describe animal movement patters at large-scale. Here, we present an approach which combines network and spatial analysis using large-scale data of six swine production companies is the US. We analyzed three years of between-premises pig movements, which include 197,022 unique animal shipments, 3,973 premises, and 391,625,374 pigs transported across 22 U.S. states. We calculated premises-to-premises movement distances and identified the main transportation routes used by each company by considering origin and destination geolocations. Furthermore, we constructed an unweighted directed temporal farm contact network at 180-day intervals to calculate farm degree loyalty. With this information, we developed an out-going farm, temporal contact chains model to obtain infection chain distributions. Model outputs were used to identify hubs in the network which can aid in developing targeted control actions via node removal over the network, and compare multiple scenarios (e.g., 5%, 10%, 15%, 20%, 25% of the farms are removed). Node removal is carried out by considering the network metrics degree, betweenness, and cluster coefficient. Our results showed that the median distance between pig premises movements was 74.37 km, with a median of 52.71 km and 328.76 km for interstate movements. On average, 2,842 premises were connected via 6,705 edges. The premises-level network exhibited a loyalty, with a median of 0.65 (IQR: 0.45 – 0.77). When targeting 25% of the premises based on degree and betweenness, we reduced the spread to 1.23% and 1.7% of infected premises, respectively. While a complete shipment movement record for the entire U.S. does not exist, our results demonstrated the value of multi-state movement data to enhance the development of outbreak mitigation tactics.