Inactivation of infectious bursal disease and Newcastle disease viruses at temperatures below 0 C using chemical disinfectants.

This study evaluated the effectiveness of bleach, Surface Decontamination Foam (SDF), and Virkon in inactivating infectious bursal disease virus (IBDV) and Newcastle disease virus (NDV) at temperatures below 0 C. To simulate the influence of organic load on the effectiveness of disinfectants, as would be encountered in disinfecting farm vehicles and equipment, the viruses were suspended in preparations containing light or heavy levels of organic matter. A small volume of the viral suspension was applied to the upper surface of stainless steel carrier disks and these were then air dried. The dried virus inoculum was covered with disinfectant to which propylene glycol had been added to prevent freezing. The disks were incubated at various temperatures for periods up to 24 hr. With NDV, at -10 C all three disinfectants in both organic preparations achieved a 5 log 10 reduction within 5 min. Results with SDF were similar at -25 and -10 C. To achieve comparable reduction with Virkon and bleach at -25 C, contact periods up to 2 or 24 hr, respectively, were required. With IBDV, to achieve a 5 log 10 to reduction by treatment with Virkon or SDF at -20 C, contact periods of 2 or 24 hr, respectively, were required in both organic preparations. It was concluded that at temperatures as low as -20 to -25 C, SDF was the most effective disinfectant for killing NDV and Virkon was most effective for killing IBDV. The finding that a contact period of up to 2 hr was required to kill IBDV, whereas NDV was killed within 5 min, attests to the greater stability of the former virus.