Advanced Control Technologies to Biocontain Aerosol Transmitted Swine Diseases

ADVANCED CONTROL TECHNOLOGIES TO BIOCONTAIN AEROSOL TRANSMITTED SWINE DISEASES

Sponsoring Institution

National Institute of Food and Agriculture

Project Status

COMPLETE

Funding Source

AFRI COMPETITIVE GRANT

Reporting Frequency

Annual

Accession No.

1025157

Grant No.

2021-68014-33655

Cumulative Award Amt.

$1,000,000.00

Proposal No.

2020-06478

Multistate No.

(N/A)

Project Start Date

Feb 1, 2021

Project End Date

Jan 31, 2025

Grant Year

2021

Program Code

[A1181]- Tactical Sciences for Agricultural Biosecurity

Recipient Organization
UNIV OF MINNESOTA
(N/A)
ST PAUL,MN 55108

Performing Department
Veterinary Population Medicine

Non Technical Summary
Airborne animal diseases are difficult to contain in today's agricultural settings. To improve biocontainment strategies and mitigate aerosol transmission of important swine pathogens, we propose a multitiered approach to investigate and optimize a novel electrostatic precipitator (ESP) design towards biocontaining aerosol transmitted swine diseases. We hypothesize that a custom designed ESP technology, both with standard wire discharge electrodes to ionize particles and drive collection, as well as secondary electrodes operated to produce reactive oxygen species, will enable new biocontainment measures to protect swine barns from airborne virus transport by their utilization on the air intake, and then transmission from barns by their utilization on the exhaust air. We will perform engineering evaluations of the physical performance, and directly examine ESP effects on airborne porcine reproductive and respiratory syndrome (PRRS) virus and influenza A virus (IAV), which are two of the most important viruses affecting pigs in the U.S. Animal studies will be used to assess the impact of the ESP technology on virus airborne transmission between infected and sentinel animals. We will integrate these aims with educational and extension efforts, including the development of courses in airborne disease transmission, biosecurity and technologies, and presentation of workshops to advance awareness, technical understanding, and use of technologies to prevent the introduction and dissemination of airborne diseases in animal populations amongst producers, policymakers, and other stakeholders. Our proposal will enable rapid response to diseases that pose large-scale biosecurity threats in animal production, including existing and imminent threats by mitigating disease spread regionally.

Animal Health Component

60%

Research Effort Categories

Basic

Applied

60%

Developmental

40%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
402	5310	2020	50%
311	4030	2020	50%

Knowledge Area
311 - Animal Diseases; 402 - Engineering Systems and Equipment;

Subject Of Investigation
5310 - Machinery and equipment; 4030 - Viruses;

Field Of Science
2020 - Engineering;

Keywords

electrostatic precipitation

swine

Goals / Objectives
The overall goal of this proposal is to improve biocontainment strategies directed at mitigating airborne transmitted diseases in food animals in order to protect the national food supply. To do so we propose to develop a novel electrostatic precipitator (ESP) for application as a biosecurity technology against aerosol transmitted infections. More specifically, we propose a multitiered approach to investigate and optimize a novel ESP design towards biocontaining aerosol transmitted swine diseases, including engineering evaluation of physical performance, direct examination of ESP effects on airborne porcine reproductive and respiratory virus (PRRSV) and influenza A virus (IAV), and animal studies of airborne disease transmission mitigation via ESP-biocontainment of infected animals. We will integrate these specific aims with educational and extension efforts, including the development of University courses in airborne disease transmission and biosecurity, and the presentation of workshops at events for the swine industry.The specific objectives are to:(1) Optimize the physical collection efficiency of a secondary ionization electrode ESP system. We will perform engineering studies to optimize the physical collection efficiency of a novel secondary ionization electrode ESP system.(2) Demonstrate a reduction in viable PRRSV and influenza virus (IAV) by the ESP technology using experimentally generated aerosols. We will examine the physical collection efficiency of the ESP for PRRSV and IAV laden particles (determined via PCR) as well as the inactivation efficiency of viable viruses (determined via cell culture).(3) Evaluate airborne transmission of PRRSV and IAV in ESP treated aerosols in pigs experimentally infected and housed under controlled conditions. Using isolation chambers with experimentally infected pigs, we will examine airborne disease transmission between animals in neighboring chambers in the absence of the ESP, and with the ESP operated including secondary electrodes. Such studies offer the unique opportunity to examine airborne virus transmission and how it can be mitigated via state-of-the-art aerosol control technology.(4) Develop a biosecurity aerosol course for undergraduate and graduate students, engineers and veterinarians. We will develop a two-week course focusing on aerosol science, control technology, and biosecurity to train a new generation of professionals towards understanding airborne disease transmission and methods to mitigate it.(5) Conduct workshops at swine industry conferences. To advance awareness, technical understanding, and use of technologies to prevent the introduction and dissemination of airborne diseases in animal populations amongst producers, policymakers, and other stakeholders.

Project Methods
Objective # 1: Optimize the physical collection efficiency of a secondary ionization electrode ESP system. Our first objective is to design and optimize the performance of the ESP. Design will be carried out using a combination of SolidWorks and openFoam software. Following the design of 3 prototype models, using oleic acid droplets (from a nebulizer) and Arizona road dust (from a fluidized bed) as the test particles, the collection efficiency of 3 prototypes at 2800 L min-1 flow rate will be determined using differential mobility analysis with condensation particle counting as well as with aerodynamic particle spectrometry. Prototypes will differ in wire spacing and wire diameter, as well as with tuned operating voltages. Measurements will be carried out in a custom wind tunnel. The ion generation rate will be determined from measurements of the current to the porous plate for both the DC primary and AC secondary electrodes. Ozone production rates will additionally be monitored for all operating conditions. In both collection efficiency and ozone measurements, we will vary the temperature and relative humidity in the system. Toluene oxidation will further be monitored by introducing controlled concentrations of toluene vapor and using a photoionization detector to determine upstream and downstream toluene concentrations. Oxidation of VOCs, occurring due to ozone and hydroxyl radicals, is indicative of the potential for virus inactivation in the ESP, and by comparing toluene oxidation rates to inactivation (subsequently described), we will assess whether the efficacy of virus inactivation can be estimated from simpler, VOC oxidation tests.Objective # 2. Demonstrate a reduction in viable PRRSV and IAV by the ESP technology using experimentally generated aerosols In order to demonstrate reduction in viable virus concentration at the ESP outlet we will aerosolize a solution of PRRSV and influenza, again using our custom wind tunnel designed for control technology evaluation. Inactivation and physical collection, known from the objective #1 engineering studies, will be distinguished from one another by utilizing both quantitative PCR and virus titer measurements.The viruses will be propagated in cell culture media and quantified. A high concentration solution of the viruses will be aerosolized upstream from the ESP. Air samples to quantify the viruses will be collected upstream and dowstream from the ESP with two distinct air collection devices. In addition, the sizes and concentrations of all particles in the chamber will be measured during tests with an optical particle counter. Tests will be run in triplicate for each of the conditions tested, which will include ESP voltages off, ESP DC electrode voltage only, and ESP DC electrode voltage and AC electrode voltage applied. The voltages chosen will be determined by the results of ozone, toluene reduction, and collection efficiency measurements.After collection, samples will be processed, stored at -80°C and tested for molecular analysis of viral RNA and cell culture quantification to assess virus viability. We expect a reduction in the concentration of viable IAV and PRRSV recovered from the ESP treated air using experimentally generated aerosols.Objective # 3: Evaluate airborne transmission of PRRSV and IAV in ESP treated aerosols in pigs experimentally infected and housed under controlled conditions.In order to evaluate the impact of ESP treated aerosols on the transmission of IAV and PRRSV, we will use experimentally infected pigs housed in chambers specially designed to evaluate aerosol transmission of viruses between animals. Pigs in the downstream chamber will only be exposed to aerosols originating from the upstream chamber (no direct pig nose to nose pig contact). If the ESP is effective, negative viral status in the downstream pigs will indicate lack of airborne transmission and effectiveness of the ESP technology at inactivating airborne viruses and preventing airborne transmission.Briefly, two isolator chambers will be connected through a 12 inches long duct containing two partitions (grids) that allows unidirectional air flow from one chamber to the other but no direct nose to nose contact between animals of the two chambers. The chambers will be operated under negative pressure to allow air movement from the upstream chamber containing the virus challenged pigs to the downstream chamber containing sentinel pigs negative to the viruses in the study. Access to the animals during the study is through specially designed glove ports that allow handling of the animals without having to open the chambers.Each pair of chambers will have 4 pigs. Two pigs will be placed in the upstream chamber (inoculated pigs) and 2 pigs in the downstream chamber (sentinel pigs). We will have 3 pairs of chambers with experimentally infected animals with the ESP system ON in order to obtain data in triplicate. We will also have 1 pair of chambers with experimentally infected pigs but without the ESP unit ON to serve as positive control, and one pair without experimentally infected animals to serve as negative control.Eighteen day-old pigs will be purchased, tested on arrival at the isolation units and pigs in the upstream chamber will be inoculated with PRRSV or IAV 48 h after arrival at the isolation units in two different studies. After inoculation, pigs will only be handled through the specially designed glove ports to avoid any cross contamination. Pigs will be sampled prior to inoculation and after inoculation at selected intervals.Objective # 4: Develop an aerosol biosecurity course for undergraduate, graduate students, engineers and veterinarians. We will develop a two-week course focusing on aerosol science, control technology, and biosecurity to train a new generation of professionals towards understanding airborne disease transmission and methods to mitigate it. The course will include in class lectures and hands on experience at the aerosol laboratories. Some of the materials will also be delivered on-line.The course will be delivered in years 2 and 3 of the grant which will allow for course evaluation and incorporation of student feed-back for improving it. The course will be evaluated by asking the students to fill out a survey to evaluate relevance of course content, effectiveness of the instructors at delivering the content, and by asking open ended questions so that specific recommendations can be incorporated in the course. We expect to at least incorporate 2 recommendations made by the students in the delivery of the course during the last year.Objective # 5: Conduct workshops at swine industry conferences to advance awareness, technical understanding, and use of technologies to prevent the introduction and dissemination of airborne diseases in animal populations.Extension related to this project involves stakeholder involvement through engagement in problem identification and input on technology development strategies for testing and implementation of the technologies working with the industry partners at the Swine Disease Eradication Center (SDEC). Extension activities will also include continuing education of broader audiences with special focus to veterinarians, producers and engineers as part of extension workshops destined to the swine industry conducted during the annual meeting of the Allen D. Leman Swine Conference, in St. Paul, MN. A modified and abridged version of this workshop will be targeted to agricultural and environmental engineers, and offered in conjunction with the American Association for Aerosol Research Annual conference (in 2022).

Progress 02/01/21 to 01/31/25

Outputs
Target Audience:Target audiences: Swine producers, veterinarians, mechanical engineers, government agencies, animal and public health officials, swine industry allied including biosecurity companies servicing the swine industry. Scientists, academics, students, postdoctoral associates, researchers, teaching faculty, extension faculty. Efforts: Publications in scientific journals, social media, lay journals, podcasts. Presentations at the Swine Disease Eradication Center (SDEC) Board meeting and technical updates to SDEC partners. The SDEC is a private/public partnerships between Academia,swine producers and private industry with the mission to discover and communicate knowledge on transmission, control and elimination of swine diseases. Organization of an Extension workshop on "New technologies and new approaches to control the spread of airborne diseases" at the Allen D. Leman Swine Conference. Development of curricula and organization and delivery of a didactic course on aerosol biosecurity entitled "Aerosol biosecurity and principles of disease transmission and prevention". Other efforts included training in laboratory methods in molecular biology, diagnostics, virology, mechanical engineering, aerosol generation, air sampling, aerosol measurements, experimental design and animal model studies. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Main training activities included mentoring and advancing professional skills and knowledge of undergraduate and graduate students, and postdoctoral fellows. Activities included experimental design, experiments execution, data collection, data processing, data analysis,results interpretation and manuscript preparation. Activities also included molecular diagnostics, virus isolation, cell culture, air sampling, sample processing, wind-tunnel set up and measurements related to aerosol science. There were opportunities to work in oral and poster presentation skills at conferences, including communication of science using infographics, poster and giving oral presentations. Students participated in conferences, workshops, in topic specific coursesand seminars. How have the results been disseminated to communities of interest?Multiple venues have been used to communicate the results of the study: - Professional meetings - American Association of Swine Veterinarians, Allen D. Leman Swine Conference, USDA ARS 8th International Biosafety and Biocontainment Symposium, - Scientific meetings - multiple conferences - Swine Disease Eradication Center Board meeting involved presenting the study to swine industry veterinarians and decision makers in production systems involved in disease control - Workshop - New technologies and new approaches to control the spread of airborne diseases took place at the 2024 Allen D. Leman Swine Conference - Seminars - multiple presentations in academic settings reaching to students interested in science, veterinary medicine, aerosol science and animal science - Podcasts - disseminated broadly to agricultural audiences - Didactic course to undergraduate, graduate,professional students (DVM) and researchers in veterinary medicine, mechanical science and public health What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Controlling the spread of airborne diseases in animals is critical to ensure an abundant safe food supply and the sustainability of animal farming. Airborne transmitted diseases in pigs are costly and difficult to prevent and contain. There is a need to develop and validate technologies able to capture and inactivate infectious aerosols, and advancetechnical understandingand use of technologies amongst producers, policymakers and other stakeholders, and help train the next generation of professionals to equip them with knowledge to mitigateairborne disease transmission. Swine producers in the Midwest currently use air filtration in sow farms to prevent the introduction ofPRRSVwhich is the most costly disease affecting pigs in the US causing losses in excess of $1 billion USD a year. Alternatives to air filtration are needed because operating air filtration systems isexpensive. Electrostatic precipitators (ESPs) which are an established technologyto control airborne particle emissions in non-agricultural settings, offer potential applications in animal farming but there is no data on their effectiveness to prevent the transmission of infectious aerosols in pigs. The studies performed here indicate that ESPs are effective at removing viruses from the air and can aid in the control of infectious diseases in pigs decreasing airborne transmission risks and the losses associated to diseases such as PRRS and influenza. The studies advanced the knowledge on conditions to operate the ESPs to maximize the removal efficiency of airborne viruses and provided a pathway for further development and validation of the ESPs under farm conditions, potentially offering a more cost effective alternative to air filtration. Furthermore, the extension and education activities performed, equipped swine industry stakeholders and the next generation of professionals in veterinary, public health and engineering with practical knowledge to help prevent the spread of airborne diseases ultimately contributing to food security, sustainability of farmingand prosperity of rural communities. In objective 1, to optimize the physical collection efficiency of a secondary ionization electrode ESP system, we designed and optimized the operating conditions for a custom-designed ESP using a single-pass wind tunnel to examine the ability of ESPs to reduce airborne transmission of viruses. For the optimization we focused on: a) physical characterization ofthe collection efficiency of the ESP for size selected particles, and 2) characterization of the charge levels of particles passing through the ESP toconfirm ionization of the particles to a high degree. We identified conditions where the ESP collection efficiency was greater than 90% for KCLparticles across a wide size range from 40 nm to 20 µm. Operating conditions included a flow through in the tunnel between 20 to 30 cfm and ESP input voltages from 11 to 14 kV. We introduced new experimental protocols to determine the charge distributions of particles after passing through the ESP to demonstrate that particles were highly charged in the devise. The results revealed Gaussian-like particle charge distribution and a power-law with exponents 1.29 and 1.39 for the average charge level as a function of particle diameter. Overall we demonstrated that the newly developed ESPcould be used to collect and removebioaerosols. In objective 2, to demonstrate a reduction in viable PRRSV and influenza virus (IAV) by the ESP technology using experimentally generated aerosols, we adapted the wind-tunnel experimental set up toaerosolizePRRSV and IAV, and sampling the viruses upstream and downstream of the ESP using cascade impactors. The setup included wind tunnel flow conditions of 30 or 50 cfm and ESP input voltage of 12 kV or 14 kV. Results for all measurements in the wind tunnel yielded log reductions increasing with particle diameters, varying from 0.2 to 2.4 for particles in the 0.1 to 10 µmaerodynamic diameter range. RT-qPCR results yielded log reductions with a similar trend, and in exceeding 3.0 logs for IAV-laden particles >8 µm. Virus titration yielded viable virus log reductions that approached 4.0 logs for larger particles of IAV.For all tested conditions, we observed a higher log reduction for larger particles. When the flow rate increased, we observed a slightly lower collection efficiency at larger particle diameters, especially >2.6 µm, but similar collection efficiency at the smaller diameters. The removal efficiency was higher when the voltage of the ESP increased from 12 to 14 kV, particularly for particles > 1 µm. We generally observed higher collection efficiency at higher voltages of the ESP, with a more pronounced effect for larger particles.Our results also indicated that there was some degree of RNA degradation/damage when viruses passed through the ESP primarily during in-flight inactivation.In summary, we demonstrated significant reductions in total and viable experimentally generated aerosols of PRRSV and IAV by the ESP technology and the results supported the testing of theESP to removebioaerosols in animals. In objective 3, to evaluate airborne transmission of PRRSV and IAV in ESP treated aerosols in pigs experimentally infected and housed under controlled conditions, we used isolator chambers with unidirectionalair flow moving from inoculated to sentinel pigs. Inoculated pigs were placedupstream of the ESPand sentinel pigs were placed downstream. Pigs did not have direct nose-to-nose contact and only the air moved from the inoculated to the sentinel pigs. Without the ESP powered, sentinel pigs became infected 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 microns 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 downtream 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 ofthis study, the ESP efficiently removed viral aerosolsand delayed the onset of IAV and PRRSV infections in the sentinel pigs. We showedthe potential of the ESPs to help prevent the spread of airborne viruses in agriculturalanimal farming facilities. In objective 4, to develop a biosecurity aerosol course for undergraduate and graduate students, engineers and veterinarians, we developed curricula and a Canvas site for the course entitled "Aerosol biosecurityand principles of disease transmission and prevention". The coursewas offered through the University of Minnesota and delivered in person to 30 registered learners. The course integrated concepts of disease transmission, aerosol transport dynamics, aerosol control technologies and disease control strategies with the goal to prepare students and professionals to more effectively assistin the control and prevention of airborne diseases in farm animals. The course received high marks by all participants who rated the course as either great or excellent. Lectures were recorded for future use. In objective 5, to conduct workshops at swine industry conferences, we organized a workshop entitled "New technologies and new approaches to control the spread of airborne diseases" that was held as part ofthe 2024 Allen D. Leman Swine Conference in St. Paul, MN. With 93 registered participants from academia, swine production, industry suppliers, veterinarians, and graduate students, theworkshop contributed with practical knowledge toadvance awareness, technical understanding, and use oftechnologies to prevent the introduction and dissemination of airborne diseases in pigs among producers, policymakers,industry allied and veterinarians.

Publications

Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: Wang L, Moran J, Yang M, Olson B, Hogan C, Torremorell M (2025). Use of an electrostatic precipitator to decrease airborne transmission of viruses in experimentally infected pigs. Proc Con Res Workers in Anim Diseases, Num 61, p42, Chicago, IL
Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: Wang L, Moran J, Yang M, Olson B, Hogan C, Torremorell M (2024). The use of an electrostatic precipitator delays the airborne transmission of influenza A virus and porcine reproductive respiratory syndrome virus in pigs. Proc Allen D. Leman Swine Conf, p:142, St. Paul, MN.
Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: Wang L, Moran J, Yang M, Olson B, Hogan C, Torremorell M (2025). Size distribution and viral load of influenza A virus-laden particles emitted from pigs over the course of infection. Proc Con Res Workers in Anim Diseases, Num 246, p97, Chicago, IL
Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: 225. Lan W, Moran J, Yang M, Olson B, Hogan C, Torremorell M (2025). Effect of an electrostatic precipitator on mitigating the transmission of airborne viruses in pigs under experimental conditions. Proc Am Assoc Swine Vets, p: 301, San Francisco, CA. https://doi.org/10.54846/am2025/128
Type: Peer Reviewed Journal Articles Status: Published Year Published: 2025 Citation: Wang L, Moran J, Yang M, Olson BA, Hogan CJ, Torremorell M (2025). Evaluation of an electrostatic precipitator in mitigating the transmission of airborne viruses in experimentally infected pigs. Vet Res 56:77 Apr 4;56(1):77. doi: 10.1186/s13567-025-01503-1.
Type: Peer Reviewed Journal Articles Status: Published Year Published: 2024 Citation: Wang L, Mor�n J, Olson BA, Yang M, Hogan CJ Jr, Torremorell M (2024). Aerodynamic Size-Dependent Collection and Inactivation of Virus-Laden Aerosol Particles in an Electrostatic Precipitator. Environ Sci Technol. 2024 Sep 11;58(38):1694151. doi: 10.1021/acs.est.4c03820. Epub ahead of print.
Type: Other Status: Submitted Year Published: 2025 Citation: Wang L, Moran J, Yang M, Olson BA, Hogan CJ Jr, Torremorell M (2025). Size distribution, viral load and estimated infectious dose of influenza virus-laden airborne particles emitted from pigs over the course of an H1N1 infection
Type: Theses/Dissertations Status: Published Year Published: 2024 Citation: Wang L (2024). Particle size characterization of virus-laden aerosols and evaluation of an electrostatic precipitator to reduce viral airborne transmission. University of Minnesota.
Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: Wang L, Moran J, Yang M, Olson B, Hogan C, Torremorell M (2025). Effect of an electrostatic precipitator on mitigating the transmission of airborne viruses in pigs under experimental conditions. USDA ARS 8th International Biosecurity and Biocontainment Symposium. Baltimore, MD
Type: Peer Reviewed Journal Articles Status: Published Year Published: 2023 Citation: Moran J, Li L, Ouyang H, Qiao Y, Olson BA, Hogan CJ (2023). Characterization of the bidimensional size and charge distribution of sub and supermicrometer particles in an electrostatic precipitator. Powder Technology 425 (2023) 118578.10.1016/j.powtec.2023.118578

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