Novel approaches to investigation and control of important viral diseases in swine populations

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Investigation of transmission of infectious agents and their successful control are important goals in the health management of swine populations. Infectious agents such as porcine reproductive and respiratory syndrome virus (PRRSV) continue to be the most important cause of mortality and production loss in swine. Although PRRSV and other pathogens circulate endemically, investigating their spread is not straightforward because many variants of the PRRSV exist and the virus continuous to evolve. Thus, epidemic spread of a newly emerging PRRSV could occur even if populations were previously exposed to another variant. Previous work indicates high level of connectivity among individual sites; either through animal movement or specialized service providers. Nonetheless, application of novel approaches such as estimation of the most likely transmission chain based on nucleotide sequence (NSeq) data could be used to assist in outbreak investigations. NSeq data should be augmented by epidemiological data such as animal movement, or other contacts among herds. The interconnectedness of herds also has consequences on the design of control strategies, both at the level of a production system and within a region. This is because interventions applied in one production phase could have implications on infection in other phases of production. Direct evidence for efficacy of such interventions applied at the level of entire production systems with multiple sites is scarce. Thus, additional approaches need to be considered to help understand dynamics of pathogens under field conditions, to investigate critical points that should be targeted for successful intervention, to conduct simulations based on relevant production systems and questions, and to evaluate results of simulations against the observed data. The overarching goal of this proposal is to integrate existing swine health data with observational and simulation studies for the purposes of efficient disease investigations, real-time surveillance of trends in disease frequency, and design of control strategies for important viral infections in swine populations. Specific objectives of this program are to: (i) determine mechanisms of spread of PRRSV among swine herds using molecular and classical epidemiological methods, (ii) establish mechanisms of ongoing processing, analysis, visualization, and interpretation of swine health data from multiple sources, (iii) further develop herd- and regional-level control models for viral infections, and (iv) characterize flow of information regarding disease control options among swine practitioners in Canada. Infectious agents that will be addressed in this proposal include PRRSV, influenza A virus, and newly emerged PEDV. Sources of data will be existing disease control programs; the data analysis will be conducted using statistical and mathematical models and network analysis.