Decontamination of fomites coming into sow farms using foggers at supply entry rooms is commonly used to mitigate associated risks. Although this practice is well established, recent research has begun to question the effect of this method to inactivate pathogens, especially in complex situations where pathogens may be shielded by organic material or blind spots.

Different combinations of temperature and time —60°C (140°F) for 10 minutes or 65°C (150°F) for 5 minutes— have been shown to be effective for inactivating pathogens in contaminated trailers or surfaces.

A study by Mafalda Pedro Mil-Homens and colleagues at Iowa State University assessed the impact of temperature and time for inactivating porcine reproductive and respiratory syndrome virus (PRRSV) and porcine epidemic diarrhea virus (PEDV) on experimentally contaminated surfaces commonly found in supply entry rooms in swine farms. The results of the study were presented as a poster during the 2022 Leman Conference.

The surfaces of two materials were tested: Diamond plate aluminum and cardboard. Four different temperatures —68°F, 86°F, 104°F and 122°F— were used in combination with six holding times —15 minutes, 60 minutes, 6 hours, 12 hours, 24 hours, and 36 hours.

The PRRSV MN184 and 1-4-4 L1C variant strains, and the NC46469/2013 PEDV isolate were used. Three replicates for each treatment were performed. Coupons were inoculated with 2 mL of virus for positive controls and test groups, or 2 mL of minimum essential medium (MEM) for negative controls. Once the surface temperature reached the desired temperature the coupons were held at the designated holding time.

The negative controls remained at room temperature for 36 hours and the positive controls remained at room temperature for 15 minutes.

Time and temperature

The PRRSV 1-4-4 L1C variant was inactivated from aluminum surfaces by heating supply entry rooms to 86°F for 12 hours and for cardboard surfaces by heating the room to 86°F for 6 hours.

Regarding PRRSV MN184, virus inactivation was possible at 86°F after 24 hours on aluminum and 104°F after 12 hours on cardboard.

PEDV inactivation was possible at 86°F after 6 hours on aluminum and 12 hours on cardboard. After 15 minute and 1-hour periods, there was only evidence of virus inactivation at 122°F in aluminum surfaces for PEDV and PRRSV 1-4-4 L1C variant.

The researchers concluded that combinations of time and temperature are workable alternatives for inactivating PRRSV and PEDV, reducing the risk of virus introduction in swine farms. Producers and farm managers can adjust combinations of time and temperature accordingly.