Stability of porcine reproductive and respiratory syndrome virus at ambient temperatures

The stability of Porcine reproductive and respiratory syndrome virus (PRRSV) was evaluated for temperatures appropriate to laboratory and field settings. Four North American (type 2) isolates (ATCC VR-2332, JA-142, MN-184, and Ingelvac® PRRS ATP vaccine virus) in cell culture medium (pH 7.5) were held at 1 of 4 temperatures (4, 10, 20, and 30°C) and sampled over time. Samples were tested for infectious virus and total PRRSV RNA using median tissue culture infectious dose and quantitative reverse transcription polymerase chain reaction, respectively. The rate of loss of infectious virus was expressed in terms of the time required for virus concentration to decline by one half (i.e., half-life [T1/2]). Statistical analysis found that temperature, but not virus isolate, had a significant effect on T1/2, and a single nonlinear regression model was derived to predict T1/2 for temperatures between 0 and 50°C: T1/2=243.54 e^{(-0.109*TEMP)}. In contrast to changes over time in the concentration of infectious virus, no change in the concentration of quantitative reverse transcription polymerase chain reaction-detectable PRRSV was detected at any temperature and contact time. This information will be of interest to persons working in laboratory or field situations in which the control of PRRSV is important.