A study funded by the Swine Health Information Center Wean-to-Harvest Biosecurity Research Program, in partnership with the Foundation for Food & Agriculture Research and Pork Checkoff, investigated the effectiveness of rapidly deployable, exhaust fan coverings to reduce the risk of airborne particles causing transmission of swine pathogens, such as porcine reproductive and respiratory syndrome virus, influenza A virus porcine epidemic diarrhea virus. Led by Erin Kettelkamp of the Swine Vet Center, this study sought to determine the most effective material to utilize for covering fans on swine barns to enhance biosecurity and reduce the spread of diseases from farm to farm. Results of the study showed that a nylon tear-resistant fan sock was the most effective material for exhaust fan coverings at reducing large airborne particle emission from the fan surface.

Read the study’s industry summary here.

SHIC, along with FFAR, a non-profit organization established in the 2014 Farm Bill, and Pork Checkoff, partnered to develop the Wean-to-Harvest Biosecurity Program to investigate research priorities in three areas – bioexclusion (keeping disease off the farm), biocontainment (after a break, keeping disease on the farm to lessen risk to neighbors), and transportation biosecurity (live haul, culls, markets, deadstock and feed haul along with innovative ways to stop pathogens from moving from markets and concentration points back to the farm). The goal of the program is to leverage funds to develop new tools and technologies that can enhance biosecurity in the wean-to-harvest phases of swine production.

To conduct this study, fan covers were tested at a single 2,400 head commercial, tunnel-ventilated, wean-to-finish site fully stocked with mid-finishing pigs. A single air space with one 24-inch pit fan, one 36-inch wall fan, and one 50-inch wall fan was enrolled. Three fan cover materials of varying permeability were evaluated, including PolyKlean synthetic air filter media (Blue Poly) that covered the fan cone, a nylon tear-resistant fan sock (Fan Sock) staked to the ground to redirect airflow, and a polyethylene privacy screen material (Black Screen) that covered the fan cone. Fan covers were compared to a fan with no cover (negative control) and materials were selected based on those that were readily available and could be rapidly deployed in an outbreak.

Airborne particle counts were collected using a handheld optical particle counter measuring particles from 0.3 to 5.0 µm. Fan coverings were assessed for their effectiveness to reduce the number of particles when compared to the negative control. Five air particle measurements were collected 1 meter from the interior of the fan shutters and 1, 2 and 3 meters from the exterior of the fan. Three consecutive air particle measurements were performed per distance and location to calculate an average particle count, with three replicates completed for each treatment and fan. Minimum ventilation pit fans and stage two pit fans ran continuously at 100% power during sample collection. Each enrolled fan ran individually at 100% power while treatments were applied. Weather conditions were recorded at all sample locations using a portable weather station.

Under the conditions of this study, the nylon tear-resistant Fan Sock had the greatest impact on reducing air particles at 1 meter outside of the fans compared to the other fan cover treatments, especially for particles measuring 5.0 µm. Conversely, the PolyKlean synthetic air filter media was the least effective at reducing airborne particle emissions from fans. However, as the distance from the fan increased, differences in airborne particle quantities were not observed across the treatments, resulting in no overall differences.

These findings suggest that implementing exhaust fan coverings would be most beneficial at reducing larger air particles up to short distances (up to 1 meter) from fans. In previous studies, virus detection and infectivity tend to correlate with larger air particle sizes. For example, PRRSV and IAV have been isolated from particles greater than 2.1 µm. In the current study, fan coverings were most effective at reducing the amount of air particles ranging from 0.7 – 5.0 µm.

Based on the relationship between air particle size and the spread of airborne swine pathogens, additional research is warranted to understand the role of fan coverings on biocontainment. The fan sock provided better airflow than the other materials evaluated and is already commonly used in the swine industry, making it a more practical option for rapid deployment during disease outbreaks to improve regional biocontainment.

Overall, exhaust fan covers can provide a rapidly employable tool for swine producers to enhance wean-to-finish site biosecurity and protect swine health. Further investigation to validate these findings and explore additional biocontainment measures is warranted.