Disinfectant effective against PEDV in freezing conditions

Contaminated hog trailers are now known to be partially responsible for spreading the porcine epidemic diarrhea virus (PEDV) in 2013 as it emerged in the US. The challenge with trucks and trailers is not just getting them clean under field conditions but to disinfect them. That effort is most difficult during winter months with freezing temperatures.

So, what are the options?

Kimberlee Baker, a veterinary student at Iowa State University, initiated a study to test the ability of a peroxygen-based disinfectant (Virkon™ S) to inactivate PEDV on aluminum surfaces with some swine feces at 4° C and -10° C.¹  She presented the results at the 2017 American Association of Swine Veterinarians’ annual meeting.

For the study, Baker replicated a typical trailer floor by constructing trays out of diamond-plated aluminum flooring. The dilution rates for the disinfectant were 1:100 and 1:600, with a contact time of 10 minutes or 30 minutes at temperatures of 4° C (39° F) or -10° C (14° F). To prevent freezing, the disinfectants tested at -10° C included 10% propylene glycol by volume.

Except for the negative-control treatment, each tray was contaminated with 2 mL of PEDV-positive feces. The disinfectant was applied according to the assigned treatment group, after which a feces/disinfectant mixture was collected and tested for infectious PEDV using a pig bioassay. Investigators orally inoculated 3-week-old barrows, housed individually, with the mixture to determine the PEDV infectivity after the disinfectant treatment. They collected rectal swabs from the pigs at 3 days and 7 days post-inoculation and tested them for PEDV. There were seven disinfectant treatment groups in all, with four replicates, four trays and four pigs per treatment.

Samples from all trays, except the negative-control group, were positive for PEDV by polymerase chain reaction (PCR) both before and after the disinfectant treatment. However, all of the pigs in the disinfectant treatment groups were negative for PEDV both 3 days and 7 days post-inoculation. It’s worth noting that PCR only detects presence of a virus’s genetic material; it does not differentiate live (infectious) virus from dead (non-infections) virus.

“The absence of infection in pigs inoculated with the disinfectant treated feces indicated that the treatments had inactivated the virus but had not destroyed its genetic material (RNA) detected by the PCR,” Baker said.

The results showed that the 1:100 and 1:600 dilution of a peroxygen-based disinfectant inactivated PEDV under freezing conditions with a short contact time.

“This provides evidence that it can be an effective option for trailer sanitation and decontamination in winter when removing organic matter and feces can be most challenging,” Baker said. “It also demonstrates that you can expect environmental swabs to test positive for PEDV by PCR even after 30 minutes of contact with a peroxygen-based disinfectant.”

She further emphasized that the study evaluated the conditions of a poorly washed trailer, not an unwashed trailer.

“It would be good to investigate whether a heavier fecal load would produce different results,” Baker concluded.

¹ Baker K, et al. Evaluation of Peroxygen-based Disinfectant to Inactivate Porcine Epidemic Diarrhea Virus in Swine Feces on Metal Surfaces Under Freezing Conditions. Student Seminar, the 48^th American Association of Swine Veterinarians’ Annual Meeting. 2017;53.