The good old farm truck — not only does it get us where we need to go and help us get the day’s tasks done, but it also carries along biosecurity risks that the industry can’t ignore.
Two different technologies were evaluated for their ability to inactivate porcine reproductive and respiratory syndrome virus (PRRSV) and porcine epidemic diarrhea virus (PEDV) on non-porous surfaces in truck cabins in a study funded through the Swine Health Information Center (SHIC)'s Wean-to-Harvest Biosecurity Research Program, in partnership with the Foundation for Food & Agriculture Research (FFAR) and the Pork Checkoff.
The study compared the use of ozone gas and purifying air-ionizing technologies. Led by Derald Holtkamp, professor of veterinary diagnostic and production animal medicine at Iowa State University, the study demonstrated the variable efficacy of ozone treatments and the lack of significant viral reduction by air-purifier treatments. This suggests that neither would be a reliable option for decontamination of truck cabins, SHIC reports in its latest newsletter.
“Several decontamination processes for truck cabins are currently available in the market, including the use of chemical disinfectants, heat treatment and ultraviolet light. However, these methods have some drawbacks, such as the potential for chemical residues, the time required for heat treatment, and the limited penetration of ultraviolet light,” SHIC reports. “As a result, there is a need for alternative decontamination methods that can effectively inactivate viruses while minimizing these drawbacks.”
Two promising alternatives for air and surface decontamination are ozone technology and air-purifier technologies. They inactivate viruses through oxidation and the generation of virucidal ions. Ozone is a powerful oxidant that can render viruses inactive by damaging the viral capsid and RNA, SHIC explains. Similarly, air-ionizing technology works by ionizing water and oxygen molecules within a room, generating virucidal ions that can inactivate viruses, bacteria, and fungal spores on surfaces. The virucidal activity of ozone against PRRSV and PEDV has been studied, but its effects at different concentrations and exposure times in truck cabins have yet to be characterized. As well, the effectiveness of air-ionizing technology for this specific application remains to be evaluated.
In this truck cabin decontamination project, a factorial design was used to test three exposure times (30, 60, and 120 minutes) and four treatment types: three ozone rates (30, 38, and 68 mg/h) and one air-ionizing technology that uses radiant catalytic ionization to purify air. Rubber coupons were contaminated with stock solutions of PRRSV and PEDV, air-dried, and exposed to treatments inside a truck cab. The rubber coupons were constructed using material similar to that used to manufacture floor mats in vehicles, SHIC reports. Coupons were placed on the truck floor to replicate real-world setting and allow exposure during treatment.
Ozone machines or air-ionizing technologies were set in the truck with an oscillating fan for continuous air circulation. The truck doors were closed and kept closed until exposure time was complete. After exposure, the viruses were collected from the coupons and titrated in cell culture to determine the reduction of infectious virus titers. In total, there were 31 treatments with four replicates each, including negative and positive controls. Humidity, temperature and ozone concentrations were recorded for all treatments.
Results of the study indicated that none of the air-ionizing treatments significantly reduced titers for either PRRSV or PEDV compared to the positive controls, SHIC reports. Ozone treatments demonstrated variable efficacy: the 30 mg/h ozone treatment significantly reduced PEDV titers at 60 and 120 minutes, and the 38 mg/h ozone treatment significantly reduced PRRSV titers at 60 minutes and PEDV titers at 120 minutes compared to controls (p < 0.05). None of the ozone treatments reduced viral titers more than two logs, which is the minimum reduction to be considered effective, the authors note.
No clear trend was observed through statistical analysis between exposure time or ozone concentration and virus inactivation. The study did find that temperature and humidity influenced ozone generation efficacy, and variations in ozone concentrations were observed even with identical machine setups. Specifically, the study identified strong positive correlations between ozone concentration and temperature inside the truck cab and moderate negative correlations between ozone concentration and humidity inside the truck cab.
“The variable efficacy of ozone treatments and the lack of significant virus reduction by air-purifier treatments suggest that under the conditions of this study, neither would be a reliable option for decontamination of truck cabins. The results also suggest that increasing ozone levels or exposure times alone may not be sufficient for reliable viral inactivation due to the complex interplay between ozone, environmental factors, and surface characteristics,” SHIC reports.
To address the challenges and achieve more effective and consistent results with ozone-based decontamination, authors noted that future research should focus on optimizing environmental controls, conducting comprehensive assessments of material compatibility and occupational health considerations, and exploring the potential for combining ozone gas with other decontamination methods.
“Overall, producers should be aware that while ozone treatments show some promise, further refinement is needed before they can be considered a reliable solution for reducing the risk of PRRSV and PEDV transmission via truck cabins in the swine industry,” SHIC reports.
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