Mitigation of airborne PRRSV transmission with UV light treatment: Proof-of-concept
Date
2021-05
Authors
Li, Peiyang
Major Professor
Advisor
Koziel, Jacek A
Zimmerman, Jeffrey J
Ramirez, Brett C
Committee Member
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Abstract
Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most economically impactful diseases to swine producers every year. Aerosols containing infectious PRRSV are an essential route of transmission, and thus proper treatment of inlet air could help mitigate the airborne spread of the virus within and between barns.
Previous bioaerosol studies focused on the microbiology of PRRSV with less focus on engineering control. Thus, Chapter 2 addressed the engineering aspects of virus aerosolization, collection, and recovery with the following objectives: (1) to build and test a virus aerosolization system, (2) to achieve a uniform and repeatable aerosol generation and recovery throughout all replicates, (3) to identify and minimize sources of variation, and (4) to verify that the collection system (impingers) performed similarly. The system for virus aerosolization was built and tested. The uniform airflow distribution was confirmed using a physical tracer (<12% relative standard deviation) for all treatments and proper engineering control of flow rates. Theoretical uncertainty analyses and mass balance calculations showed a <3% loss of mass flow rate of air between the inlet and outlet. A comparison of TCID50 values among impinger fluids showed no statistical difference between any two of the three trials (p-value = 0.148, 0.357, 0.846). The results showed that the system could perform consistently in virus aerosolization and collection, which supports the readiness of subsequent research on PRRSV treatment, which was addressed in Chapter 3 with the incorporation of ultraviolet (UV) light.
Building upon Chapter 2, Chapter 3 quantified the effectiveness of ultraviolet (UV) in inactivating aerosolized PRRSV, specifically, four UV lamps, UV-A (365 nm, both fluorescent and LED-based), "excimer" UV-C (222 nm), and germicidal UV-C (254 nm), were tested for this purpose. The two UV-C lamps effectively irradiated fast-moving PRRSV aerosols with short treatment times (<2 s), whereas the UV-A (365 nm, both fluorescent and LED-based) lamps could not reduce PRRSV titers for tested doses up to 4.11 mJ/cm2. Based on experimental data, both one-stage and two-stage UV inactivation models estimated the UV doses needed for target percentage (%) reductions on viable PRRSV titer. The UV-C (254 nm) and UV-C (222 nm) doses needed for a 3-log (99.9%) reduction were 0.521 and 0.0943 mJ/cm2, and 0.0882 and 0.048 mJ/cm2, respectively, based on one-stage and two-stage models. An order of magnitude lower dose for UV-C (222 nm) than UV-C (254 nm) doses was needed for a 3-log reduction. While the cost of 222-nm excimer lamps is still economically prohibitive for scaling-up trials, pilot-scale or farm-scale testing of UV-C (254 nm) on PRRSV aerosols simulating barn ventilation rates are still recommended based on its effectiveness and reasonable costs comparable to high-efficiency particulate air (HEPA) filtration.
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