Comparative survival of ten porcine reproductive and respiratory syndrome virus strains at three temperatures

Objective: Comparative survival of 10 strains of porcine reproductive and respiratory syndrome virus (PRRSV) at 3 temperatures. Materials and methods: Strains of PRRSV were propagated in MARC-145 cell line. Aliquots of virus were placed in the bottom of wells on 24-well plates at 100 µL per well. After the virus inoculum was dry, the plates were stored at one of 3 temperatures (4°C, room temperature [22°C-25°C], or 37°C). The surviving virus was eluted at different time points and then titrated. Results: All 10 strains survived for at least 35 days at 4°C but showed variability in percent survival. For example, the percent survival of strains 1-7-4, Lelystad, 1-8-4, VR-2332, 1-4-2, and 1-4-4 MN was greater (0.29%-2.19%) than that of the other 5 strains (0.01%-0.03%). At room temperature, 5 strains (VR-2332, Lelystad, 1-4-4 SD, 1-4-4 MN, and 1-8-4) survived between 3 and 7 days while the other 5 survived for 1 day only. Four of the ten strains (Lelystad, 1-4-4 MN, 1-4-4 SD, and 1-8-4) survived for up to 3 days at 37°C and the remaining 6 strains for 1 day only. The recently emerged variant 1-4-4 L1C was one of the more resistant strains surviving for 7 days at room temperature and 3 days at 37°C. Implications: There were differences in the survival of different PRRSV strains at different temperatures, which should be taken into consideration for designing effective biosecurity practices including disinfection regimens.