Key result
Repeated mass immunization with herd closure or gilt acclimatization was the most likely strategy to achieve a stabilized status against PRRS virus in simulated swine farms.
Mathematical modeling suggests that repeated mass immunization combined with herd closure or gilt acclimatization is the most effective strategy for controlling PRRS virus outbreaks on swine farms.
May guide PRRS stabilization modeling in swine; leaves open prospective farm validation before adoption.
OBJECTIVE: To use mathematical modeling to assess the effectiveness of control strategies for porcine reproductive and respiratory syndrome (PRRS) virus on a swine farm. SAMPLE: A hypothetical small, medium, or large farrow-to-weaning swine farm in the Midwestern United States. PROCEDURES: Stochastic models were formulated to simulate an outbreak of PRRS on a farm. Control strategies assessed in those models included none (baseline) and various combinations of mass immunization, herd closure, and gilt acclimatization. Nine different models resulting from the combination of low, moderate, or high PRRS virus virulence and small, medium, or large herd size were simulated. A stabilized status, the outcome of interest, was defined as the absence of positive PCR assay results for PRRS virus in 3-week-old piglets. For each scenario, the percentage of simulations with a stabilized status was used as a proxy for the probability of disease control. RESULTS: Increasing PRRS virus virulence and herd size were negatively associated with the probability of achieving a stabilized status. Repeated mass immunization with herd closure or gilt acclimitization was a better alternative than was single mass immunization for disease control within a farm. CONCLUSIONS AND CLINICAL RELEVANCE: Repeated mass immunization with a PRRS modified-live virus vaccine with herd closure or gilt acclimitization was the scenario most likely to achieve a stabilized status. Estimation of the cost of various PRRS control strategies is necessary.
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Jeong et al. (2014) studied Porcine reproductive and respiratory syndrome (PRRS). Combinations of mass immunization, herd closure, and gilt acclimatization vs. None (baseline) was evaluated on Stabilized status (absence of positive PCR assay results for PRRS virus in 3-week-old piglets). Repeated mass immunization with herd closure or gilt acclimatization was the most likely strategy to achieve a stabilized status against PRRS virus in simulated swine farms.
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