Risk analysis of infectious disease in pigs in Gifu prefecture, Japan, through network analysis

Movements of livestock, humans, vehicles and wildlife are recognized as critical contributors to the spread of infectious diseases in livestock and can be modeled as a network to assess and predict disease transmission. This study developed a comprehensive multilayer network incorporating the movements of pigs, humans, vehicles, and, presumably, wild boars to estimate the risks of disease introduction and transmission for each husbandry stakeholder and to identify key clusters and modes of movement involved. A questionnaire-based study was conducted across 22 pig farms in Gifu Prefecture, Japan, collecting data on pig, human, and vehicle movements to establish networks. The wild boar movement network was estimated using data on pig farm locations and wild boar habitats collected from vegetation cover data. Movement-associated effects in each network based on movement frequency were assigned to combinations of the four networks, resulting in a four-layered network. The network exhibited small-world characteristics and was clustered into four groups. Disease containment schemes in livestock are commonly established along administrative boundaries, however these four epidemiological clusters, comprising 31, 28, 24, and 22 nodes, did not align exactly with administrative districts, suggesting the significance of managing livestock infectious diseases beyond governmental borders. In the Partial Least Squares Regression (PLSR) analysis, pig, vehicle, and wild boar movement made comparable positive contributions to PageRank-based node importance within the multilayer network. This study highlights the significance of epidemiological links among husbandry and nonhusbandry stakeholders, emphasizing the need to develop effective risk management tools considering the probable disease transmission pathways.