Enhancing detection of porcine reproductive and respiratory syndrome virus RNA in processing fluids stored at room temperature using PrimeStore molecular transport medium

Porcine reproductive and respiratory syndrome virus (PRRSV) is a significant pathogen affecting the U.S. swine industry, resulting in substantial costs associated with disease prevention, elimination, and control. Processing fluids (PFs) are an increasingly popular sample type for PRRSV surveillance due to their cost-effectiveness and high herd-level sensitivity. However, like other aggregate sample types, PF samples are non-pristine, and the RNA within them is susceptible to degradation, increasing the risk of false-negative and/or inconsistent results in reverse-transcription real-time PCR (RT-rtPCR) testing. We evaluated the efficacy of the nucleic acid-preserving reagent PrimeStore molecular transport medium (PS-MTM) in improving PRRSV RT-rtPCR detection rates, Ct values, and whole-genome sequencing (WGS) outcomes in PF samples. We collected PF samples from 2 PRRSV-positive sow herds and divided them into untreated controls and 2 PS-MTM-treated groups. PS-MTM-treated PFs had significantly lower Ct values compared to untreated samples, indicating improved RNA preservation and detectability. Although sequencing outcomes varied between study groups, PS-MTM-treated samples had statistically higher unique read counts. However, differences in other measured sequencing outcomes between the study groups were not statistically significant. PS-MTM has potential in PF sampling protocols to enhance PRRSV surveillance accuracy by reducing false-negative RT-rtPCR results.