Today, we are sharing a recent publication from the Torremorell lab exploring a new technology aiming at preventing the transmission of airborne viruses. The full publication is available in open access on the Veterinary Research journal.

Methods

• Electrostatic precipitators (ESP) are air cleaning devices removing particles from the air and depositing them on collection surfaces.
• 4 pigs were inoculated with either PRRSV or influenza A virus (IAV) and placed into two isolators linked through an air duct.
• The air then went through an ESP prior to reaching 2 naive pigs placed in a third isolator. (see figure below)

• The study lasted until the sentinel pigs were confirmed positive or the study went on for 10 days, whichever came first.
• Nasal swabs were collected each day and tested for PRRSV or IAV by Rt-PCR, blood samples were collected at day 3, 6 and 10 and tested for PRRSV.
• Air samples and environmental samples were collected daily and tested for PRRSV and IAV as well.
• Studies were repeated 5 times for each virus: twice with the ESP turned off, twice with the ESP at a lower setting and once with the ESP set at a higher setting.

Results

• Nasal swabs from the sentinel pigs were tested positive sooner when the ESP was turned off (day 2 versus day 5-7 for IAV; day 2 versus day 7-10 for PRRSV)
• On average, a 1.51 to 3.48 log reduction of IAV RNA concentration in the air was observed whereas PRRSV could not be detected in the air both upstream and downstream of the EPS, except towards the end of the positive control experiment (no ESP).

Abstract

Airborne viruses spread rapidly in animal premises, which makes them difficult to contain. Electrostatic precipitators (ESP) are air cleaning devices that charge airborne particles and electrophoretically deposit them on collection surfaces, thereby removing them from an airstream. We evaluated the effect of a single-stage wire-plate ESP on mitigating airborne transmission of influenza A virus (IAV) and porcine reproductive and respiratory syndrome virus (PRRSV), using experimentally infected pigs. Inoculated pigs were placed in isolators upstream of the ESP, and sentinel pigs were placed downstream in an isolator. The airflow moved unidirectionally from inoculated pigs to sentinel pigs. Nasal swabs of pigs, air samples and surface wipes from all the isolators were collected daily and tested by RT-qPCR. Without the ESP powered, sentinel pigs tested positive within 1 day of exposure to IAV aerosols and 2 days to PRRSV aerosols. Airborne IAV RNA was detected upstream and downstream of the ESP in particles ranging from 0.22 μm to > 8 μm. In contrast, with the ESP powered, sentinel pigs tested positive after 5–6 days of exposure to IAV aerosols, and 7–8 days to PRRSV aerosols. Limited levels of IAV RNA were detected in air samples in the downstream isolator before sentinel pigs tested positive. The RNA-based virus removal efficiency of the ESP ranged from 96.91 to 99.97%, with higher removal observed in particles > 6.5 μm. Under the conditions of this study, the ESP efficiently removed IAV aerosol particles and delayed the onset of IAV and PRRSV infections in the sentinel pigs. Our study shows the potential of the ESPs to help prevent the spread of airborne viruses in agricultural animal farming facilities.