A study funded through the Swine Health Information Center’s Wean-to-Harvest Biosecurity Research Program, in partnership with the Foundation for Food & Agriculture Research and the Pork Checkoff, recently evaluated the effectiveness of two different technologies for their ability to inactivate porcine reproductive and respiratory syndrome virus and porcine epidemic diarrhea virus on non-porous surfaces in truck cabins. Led by Derald Holtkamp at Iowa State University, the study compared the use of ozone gas and purifying air-ionizing technologies. Results demonstrating the variable efficacy of ozone treatments and the lack of significant viral reduction by air-purifier treatments suggest that neither would be a reliable option for decontamination of truck cabins. Additional research is warranted to identify a consistent, effective and practical decontamination strategy for cabs of livestock trucks.

Several decontamination processes for truck cabins are currently available in the market, including the use of chemical disinfectants, heat treatment and ultraviolet light (Thomas et al., 2015). 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 (Gosling et al., 2017). As a result, there is a need for alternative decontamination methods that can effectively inactivate viruses while minimizing these drawbacks.

Ozone technology and air-purifier technologies have emerged as promising alternatives for air and surface decontamination by inactivating viruses through oxidation and the generation of virucidal ions (Tseng & Li, 2008; Sharma & Hudson, 2008). Ozone is a powerful oxidant that can render viruses inactive by damaging the viral capsid and RNA (Tseng & Li, 2008). 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 (Nikitin et al., 2014). Although the virucidal activity of ozone against PRRSV and PEDV has been studied, its effects at different concentrations and exposure times in truck cabins have yet to be characterized. Likewise, the effectiveness of air-ionizing technology for this specific application remains to be evaluated.

In the current truck cabin decontamination study, 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 device (ActivePure) 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. Coupons were placed on the truck floor to replicate real-world setting and allow exposure during treatment.

Ozone machines or ActivePure devices were placed inside the truck, along with an oscillating fan for continuous air circulation. Once the equipment was in place and turned on, the truck doors were closed and the doors remained 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. Data loggers recorded humidity and temperature for all treatments, and ozone meters monitored ozone concentrations.

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. 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.

Statistical analysis revealed no clear trend between exposure time or ozone concentration and virus inactivation. However, the study found 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 (r = 0.5, p < 0.0001) and moderate negative correlations between ozone concentration and humidity inside the truck cab (r = -0.56, p < 0.0001).

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. To address the challenges and achieve more effective and consistent results with ozone-based decontamination, 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. Investigating these aspects in greater depth will be crucial for developing reliable viral inactivation strategies in swine logistics settings.

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.