Progress 02/01/23 to 01/31/24

Outputs
Target Audience:Significant efforts were made to reach out various audiences. Scientists interested in animal diseases, biosecurity and disease prevention. Information was presented at various conference meetings and also through a podcast. Information was also presented to swine producers, veterinarians and industry allied attending the conferences. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The main training activities achieved so far have been directed at advancing professional skills and knowledge of undergraduate andgraduate students, and postdoctoral fellows. These include laboratory activities in mechanical engineering labs that entail data collection, data processing, data analysis and results interpretation. Activities in virology have centered in advancing skills of graduate students in cell culture methods and molecular diagnostic methods. Activities also included training students in animal models using pigs as a model and in particular to conduct experimental infections, sample collection, sample processing, testing and results interpretation. Students have also have the opportunity to improve presentation skills at conference meetings, including communication of science using infographics,posters and giving oral presentations. How have the results been disseminated to communities of interest?Dissemination of knowledge occurred in the scientific community and to lay audiences. A poster of this work was presented in person at the 2023 Allen D. Leman Swine Conference which is a conference that attracts swine industry specialistsand scientists from the US and from more than 20 countries. The work was also dissemination in the form of oral presentations at the 2023 North American International PRRS sysmposium and at the 2024 Conference of Research Workers in Animal Diseases. Dissemination also occurred via a video podcast offered to swine audiences given the applicability of the results and the potential benefits to the swine industry. What do you plan to do during the next reporting period to accomplish the goals?Our next steps will focus on publishing the work conducted to date in refereed journals. We will also focus on completing the education and outreach goals of the study that consist in developing a course on bioaerosols, aerosols science, control technologiesand biosecurity to train the next generation of professionals to understand airborne disease transmission and methods to mitigate it. We will also conduct a workshop at a swine industry conference to advance awareness, technical use and understanding of technologies to prevent the introduction and dissemination of airborne diseases in animals.

Impacts
What was accomplished under these goals? Controling the spread of airborne diseases is critical to ensure food security and sustainability of farming.Because airborne transmitted diseases are difficultto contain, there is a need to develop and validate strategies and technologies directed at capturing and inactivating bioaerosols emitted by animals. By preventing the spread of economically significant diseases in animals, we will contribute to food security and prosperity of rural and farm communities. Swine producers continue to invest in technologies that mitigate the introduction of airborne diseases into farms. Currently air filtration is the only technology being implemented in swine farms to prevent the introduction of airborne diseases. However, air filtration is costly and causes pressure drop in the ventilation systemthat results in increased energy costs and potential air leakage of non-filtered air. Thus, there is a need to develop cost-effective technologies deployable to farms to prevent the introduction and spread of airborne diseases. Electrostatic precipitators (ESPs) are an established technology in non-agricultural settings that offerpotential applications to swine farms. As part of this study, we have developed an ESP that has been optimized in the lab to capture virus-laden particles that resulted in log reductions oftotal and viable viruses. In the past year, we testedthe ESP in an experimental setting with animals to evaluate whether the ESP could mitigate the transmission of two important viruses affecting pigs, PRRSV (porcine reproductive and respiratory syndrome virus) and (IAV) influenza A virus. We used a modular animal isolator system specially designed to house animals under BSL-2 conditions that consisted of three air-tigth self-contained isolators operated under negative ventilation and that were connected with ducts that allowed unidirectional air flow from isolator 1, to isolator 2 and to isolator 3. The isolators did not allow for direct nose-to-nose contact between the pigs in each isolator. The ESP was installed between isolator 2 and 3 and air measurements to detect virus-laden particles took place upstream and downstream of the ESP. Pigs upstream of the ESP were inoculated withPRRSV and IAV in different tests (seeder pigs), while pigs downstream of the ESP were naive to the viruses (sentinels). For each virus, we conducted a positive control test with the ESP OFFand 3 tests with the ESP ON (two with the ESP operating at 12 Kv and one operating at 13 Kv). During each test we collected air samples upstream and downstream of the ESP, and pig samples each day of the study to evaluate whether there was transport of virus-laden particles that resulted in transmission and infection of the viruses to the sentinel pigs. When the ESP system was OFF, we showed transmission ofPRRSV and IAV from the seeder to sentinel pigs within 24-48 h of inoculation of the seeder pigs indicating that our experimental model was effective at transmitting the virus via contaminated air. When the ESP system was ON, transmission was delayed and only observed in the sentinel pigs after being exposed for5 to 6 days to the aerosols originating from the seeder pigs. IAV was detectedupstream and downstream in the air samples when the ESP system was OFF. Detection of airborne IAV when the system was ONwas possible downtream but at a much lower concentration. We estimated a total log reduction of 1.5 to 4.2 airborne IAV RNA copies/m3 by the ESP.In the case of PRRSV, detection of the virus in air samples was only possible during the ESP OFF and at low concentrations including in the experimentally inoculated pigs. We did not detect PRRSV in the air samples collected downstream when the ESP was ON despite the fact that PRRSV could be transmitted to sentinel pigs. In summary, under the conditions of this study, we showed that the ESP was able to significantly reduce the concentration of viruses from the air which resulted in a significant delay in the transmission of the viruses to sentinel pigs.

Publications

• Type: Conference Papers and Presentations Status: Submitted Year Published: 2024 Citation: Wang L, Moran J, Yang M, Olson B, Hogan C, Torremorell M. The effect of an electrostatic precipitator on mitigating aerosol transmission of influenza A virus in pigs. Conference of Research Workers in Animal Diseases, Chicago, January 21-23, 2024
• Type: Conference Papers and Presentations Status: Published Year Published: 2023 Citation: Development and evaluation of an electrostatic precipitator (ESP) prototype to mitigate airborne spread of pathogens under farm conditions, NA PRRS Symposium, 2023 NAPRRS/NC229: International Conference of Swine Viral Diseases, Chicago, November 30 - December 2, 2023.
• Type: Conference Papers and Presentations Status: Published Year Published: 2023 Citation: Wang L, Moran J, Yang M, Olson B, Hogan C, Torremorell M. Evaluation of an electrostatic precipitator on PRRS virus aerosol removal and inactivation (2023). Proc Allen D. Leman Conference, p: 91-92. St. Paul, MN.

Progress 02/01/22 to 01/31/23

Outputs
Target Audience:Scientists interested in animal diseases, biosecurity and disease prevention. Information was presented at a conference meeting. Swine producers, veterinarians and industry attending a technical meeting/workshop. Changes/Problems:A delay of about 6 months occurred for our animal studies due to unexpected leakage observed in the animal isolation chambers. The leakage have been repaired and animal studies should start this spring. What opportunities for training and professional development has the project provided?The main training activities achieved so far have been directed at advancing professional skills and knowledge of undergraduate and graduate students. These include laboratory activities in mechanical engineering labs that entail data collection, data processing, data analysis and results interpretation. Activities in virology laboratories have centered in advancing skills of graduate students in cell culture methods and molecular diagnostic methods. Students have also have the opportunity to improve presentation skills at conference meetings, including communication of science using infographics and posters. How have the results been disseminated to communities of interest?Dissemination of knowledge occurred in the scientific community. A poster of this work was presented in person at the 2023 Conference of Research Workers in Animal Diseases. Dissemination also occurred in a workshop organized by the University of Minnesota Swine Disease Eradicaiton Center that included as participants veterinarians, producers and industry allied. What do you plan to do during the next reporting period to accomplish the goals?Our next steps in ESP evaluation are to test the collection and inactivation of influenza virus (IAV) in aerosols passing through the ESP. In doing so, we will use similar flow rates and the highest ESP operating voltage (14 kV), maximizing collection efficiency and reactive oxygen species generation. We will sample virus-laden aerosols upstream and downstream of the ESP, using titration and RT-qPCR to quantify total removal efficiency (collection+inactivation) and physical removal (nucleic acid only). Ozone concentrations and VOC oxidation will also be monitored under these conditions. We will also plan and execute studies using experimentally infected animals to assess the effectiveness of the ESP technology at preventing the transmission of viral aerosols between infected and non-infected animals.

Impacts
What was accomplished under these goals? Controlling the spread of animal diseases is critical to protect the food supply, the viability of farming and the sustainability of food production systems. Because airborne transmitted diseases are difficult to contain there is a need to develop technologies and approaches directed at capturing virus-laden aerosols before they become emitted from farms. By preventing the spread of economically significant diseases between farms, we will contribute to food security and the prosperity of rural and farm communities. Currently there are very few aerosol technologies applicable to protecting animals in farm settings and the limited ones (i.e air filtration) are costly and maintenance is cumbersome. Thus there is a need to develop new technologies with the prospect to apply them to farm animals in confinement. Electrostatic precipitators (ESPs) are an established technology in non-agricultural settings used towards the collection of ultrafine and submicrometer particles at industrially relevant scales because they can efficiently collect particles without having high flow pressure drops. However, proper ESP design for high collection efficiency is often complicated by the fact that the unipolar charging process, necessary to yield multiply charged particles which are readily collected, is complex, depending upon the ion properties and spatial concentration, as well as the fluid flow and ESP geometry. In the past year, we finalized the design and optimized the operating conditions for a custom-designed parallel plate electrostatic precipitator (ESP) using a single-pass wind tunnel, targeting application in animal studies to examine the ability of ESPs to reduce airborne transmission of viruses. Optimization relied upon two steps: (1) physical characterization of the collection efficiency of the ESP for size selected particles, and (2) characterization of the charge levels on particles passing through the ESP, to confirm particles are ionized to a high degree. In this context,we have identified operating conditions under which the ESP collection efficiency is greater than 90% for KCl spherical particles across a wide size range from 40 nm to 20μm. These operating conditions include a flow through the wind tunnel between 20 to 30 cfm and ESP input voltages from 11 to 14 kV. We have also introduced new experimental protocols to determine the charge distributions of particles after passing through the ESP to demonstrate that particles are highly charged in the device. To this end, we have used aerosol measurement instruments including a differential mobility analyzer (DMA), aerodynamic particle sizer (APS), and a condensation particle counter (CPC). These new experimental protocols include the development of inversion routines to account for the instruments transmission and penetration efficiency which is necessary to yield highly accurate measurements. The results reveal clear Gaussian-like particle charge distribution for fixed particle sizes. Also, a power-law with exponents 1.29 and 1.39 is observed for the average charge level as a function of particle diameter. Similarly, the corresponding variance is also monotonically increasing with the particle diameter. In addition, and to gain better understanding on the particle charging phenomenon, we have introduced a simple 1d numerical model able to predict the experimental trends with reasonable accuracy. This numerical model considered the particle deposition through electrophoresis as well as particle charging through two different mechanisms namely diffusion and field charging. The end result is demonstration that the proposed and developed ESP can now be tested in its ability to collect/remove bioaerosols and prevent airborne infection spread in animal model experiments. In order to test the ability of the ESP to remove bioaerosols, we adapted our experimental setup for sampling porcine reproductive and respiratory syndrome virus (PRRSV) bioaerosols upstream and downstream of the ESP using non-viable Andersen cascade impactors. The experimental setup with PRRSV aerosols included wind tunnel flow conditions of 30 or 50 cfm and ESP input voltage test of 12 kV or 14 kV. Overall we observed average total log reductions ranging of 0.69 RNA copies/mL and 1.07 TCID50/mL (30 cfm, 12kV), 1.25 RNA copies/mL and 1.53 TCID50/mL (30 cfm, 14 kV) and 0.10 RNA copies/mL and 0.88 TCID50/mL (50 cfm, 14 kV). These results demonstrate a reduction in viable PRRSV by the ESP technology using experimentally generated aerosols.

Publications

• Type: Conference Papers and Presentations Status: Published Year Published: 2023 Citation: Torremorell M, Wang L, Yang M, Cofre JM, Olson B, Li L, Hogan C (2023). Evaluation of an electrostatic precipitator on PRRS virus aerosol removal and inactivation. [Poster]. Conference of Research Workers in Animal Diseases, Chicago, January 22-24, 2023.

Progress 02/01/21 to 01/31/22

Outputs
Target Audience:Graduate and undergraduate students participating in lab activites related to conducting the research. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The main training activities achieved so far have been directed at advancing professional skills and knowledge of undergraduate and graduate students. These include laboratory activities in mechanical engineering labs that entail data collection, data processing, data analysis and results interpretation. Activities in virology laboratories have centered in advancing skills of graduate students in cell culture methods and molecular diagnostic methods. How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?Our next steps in ESP operation are to test the simultaneous collection and inactivation of viruses (PRRSV) in aerosols passing through the ESP. In doing so, we will use 1-2 flow rates (likely 1420 L min-1) and the highest ESP operating voltage (14 kV), maximizing collection efficiency and reactive oxygen species generation. We will sample virus-laden aerosols upstream and downstream of the ESP, using titration and RT-qPCR to quantify total removal efficiency (collection+inactivation) and physical removal (nucleic acid only). The difference between these two metrics will yield the virus inactivation efficiency. Ozone concentrations and VOC oxidation will also be monitored under these conditions. We will also start the planning and execution of studies using experimentally infected animals to assess the effectiveness of the ESP technology at preventing the transmission of viral aerosols between infected and non-infected animals.

Impacts
What was accomplished under these goals? Controlling the spread of animal diseases is critical to protect the food supply, the viability of farmers and the sustainability of food production systems. Because airborne transmitted diseases are difficult to contain there is a need to develop technologies and approaches directed at capturing virus laden aerosols before they become emitted from farms. By preventing the spread of economically significant diseases between farms and regions, we will contribute to having a stronger food supply and prosperity of rural and farm communities. In the first year we have successfully designed, built, and tested a parallel plate ESP (electrostatic precipitator) with the option for secondary ionization electrodes. We have experimentally tested the collection efficiency of the ESP for variable applied voltages (10-14 kV, where we obtain a corona discharge) and air flow rates in the 280 L min-1 to 2300 L min-1 range. In general, the ESP has a collection efficiency in excess of 90% for particles larger than 1 micrometer in diameter, and for smaller particles, with a minimum in collection efficiency near 70% in the 100-300 nm size range. Overall, we have a large data of ESP performance for more than 10 flow rate-applied voltage combinations, with particle collection efficiency determined in the 10 nm - 5 micrometer diameter range (a wide size range). We are presently analyzing results to determine if a simple equation (based on the traditional Deutsch-Anderson equation) can be used to predict the collection efficiency for particles across a wide range of ESP operating conditions.

Publications