The goals of this study were to demonstrate the true risk posed by the entry of PRRS virus-contaminated aerosols through unfiltered points (e.g. idle fans), to determine the minimum air speed necessary for introduction of PRRSV-contaminated aerosols, and to validate available interventions that have been designed to prevent this risk. The study was conducted using an empty facility, where one of two fans was intentionally stopped and the other continued to operate. A common plastic shutter was challenged at various fan stages using 10 replicates of different PRRSV concentrations. The available intervention methods tested included the standard plastic shutter, a plastic shutter plus a canvas cover, a nylon windsock, an aluminum shutter plus a windsock and, a double shutter system (aluminum and plastic shutters). Results from this study indicate that retrograde air movement is a risk for PRRSV introduction in filtered farms. The results suggest that a real risk of PRRSV exists at a minimum retrograde air speed of 0.76 m/s. Results show that not all interventions designed to reduce this risk are effective, suggesting that plastic shutters and canvas covers do not offer complete protection against the entry of PRRS aerosols.
Principal Investigator: Scott A. Dee, University of Minnesota
Source: Pork Checkoff Research Review, July – August, 2012