Sixteen-year longitudinal study assessing the effects of air filtration on the occurrence of porcine reproductive and respiratory syndrome in breeding herds

Infectious diseases in livestock pose ongoing risks to food security, animal and public health, with swine pathogens capable of spreading over long distances through aerosols. Air filtration has become a key biosecurity intervention to mitigate the risk of airborne transmission, particularly for porcine reproductive and respiratory syndrome (PRRS), a major disease that burdens the swine industry. While the effectiveness of air filtration is well documented, limited research has evaluated its long-term impact while accounting for ventilation pressure and regional pig density. This study estimated the effect of air filtration approach (year-round vs partial-year) and pressure type (positive vs negative) on the occurrence of PRRS in U.S. sow herds. This study analyzed 16 years (2009–2024) of longitudinal data from 25 production systems in 12 states, representing about 1.6 million sows, including 245 non-filtered and 178 filtered farms. Generalized additive models with a negative binomial distribution were used to assess the effects of air filtration status on the total number of PRRS outbreaks per farm, incorporating Gaussian process smooths for spatial autocorrelation. Compared to non-filtered farms, those with year-round and partial-year air filtration showed significantly lower PRRS incidence rates, with 0.494 times (P < 0.001) and 0.502 times (P = 0.006) the incidence rate of non-filtered farms, respectively. Farms with negative-pressure filtration had 0.492 times (P < 0.001) the incidence rate, while positive-pressure farms showed 0.416 times (P < 0.001) the incidence rate of non-filtered farms. A temporal sub-analysis revealed that the protective effect of air filtration increased over time. This study offers valuable evidence on the effects of different air filtration approaches on PRRS occurrence while accounting for regional disease burden and ventilation pressure. Altogether, the findings provide solid long-term, field-based evidence to inform air filtration decisions and guide tailored biosecurity planning across diverse production systems.