Date Full Report Received10/02/2017
Date Abstract Report Received
Funded ByNational Pork Board
Two of the primary goals in the National Pork Board (NPB) strategic plan call for the development and deployment of mitigation strategies capable of eliminating the top domestic swine diseases, including decreasing the annual economic impact of porcine reproductive and respiratory syndrome (PRRS) by 20%. Particulate filters installed on hog barn ventilation air intakes increase operating costs through the need for periodic filter replacement, and can be rendered ineffective by any leaks that appear in what must otherwise be an airtight building structure. Other reported challenges of air filters include reduced cooling capacity and shorter than expected filter life/more frequently than expected filter replacement. In its 2016 request for proposals, NPB sought practical systems for inactivating PRRSV in commercial farm settings.
Plasmas represent an ionized state of matter in which atoms and molecules lose or acquire excess charge as they collide with free electrons, all of which results in a highly chemically reactive environment. While conventional combustion flames represent thermal plasmas, non-thermal plasmas are induced by electromagnetic and other means and lack the high temperatures of thermal plasmas. This project tests the effectiveness of a prototype non-thermal plasma (NTP) reactor to inactivate airborne PRRSv. PRRSv was suspended in the air at the entrance to a small wind tunnel using a mister supplied with a liquid solution containing active PRRSv. The PRRSv aerosols were then exposed to a region of non-thermal plasma within a prototype NTP reactor installed in the wind tunnel test section. Lab analyses of the PRRSv collected from the airstream upstream and downstream of the NTP reactor by identical liquid impingers provided pre- and post-treatment TCID50, a measure of the abundance of an infectious viable agent. The reduction in TCID50 following NTP treatment, after adjusting for the loss of PRRSv between the two collection points, represents the inactivation efficiency achieved by the NTP reactor for a given set of experimental conditions. The results showed that PRRSv was inactivated to a similar degree as a different virus, MS2 phage, at the same conditions, e.g., 1.3-log (> 90%) inactivation of PRRSv achieved at an applied voltage of 20 kV and an air flow rate of 12 cfm. Differential pressure across the reactor was minimal compared to that imposed by HEPA filters. A high porosity consumer-grade ozone filter positioned downstream of the reactor effectively reduced residual ozone concentrations down to levels commensurate with the ambient laboratory environment. The results demonstrate the potential of NTPs, once properly optimized, for the prevention of airborne PRRSv transmission into hog barns with ventilation air. An optimized NTP airstream sterilization system would: 1) reduce or eliminate the need to retrofit facilities to establish an air-tight building envelope, 2) eliminate the expense and waste of replacing and disposing of used air filters, 3) offer protection from airborne viruses irrespective of viral mutations, 4) offer protection that is on-demand or tunable as meteorological or climatic conditions warrant.