Efficient Biosafe Inactivation of Classical Swine Fever Virus While Preserving Viral RNA for Molecular Diagnosis

Classical swine fever (CSF) is a highly contagious transboundary animal disease that causes major economic losses to the global swine industry and remains notifiable to the World Organisation for Animal Health (WOAH). Handling and transport of infectious classical swine fever virus (CSFV)-positive samples require biosafety level 3 (BSL-3) containment, limiting diagnostic capacity and interlaboratory exchange in many regions. In this study, we evaluated the efficacy of PrimeStore^® Molecular Transport Medium (PS-MTM) for eliminating detectable CSFV infectivity while preserving viral ribonucleic acid (RNA) detectability for downstream molecular detection. Validation assays were performed using the CSFV Alfort/187 reference strain and clinical samples collected from pigs experimentally infected with the Catalonia01 and Margarita CSFV strains. Residual infectivity was assessed by virus isolation, whereas viral RNA detection and stability were evaluated using the WOAH-recommended real-time reverse transcription quantitative polymerase chain reaction(RT-qPCR) assay. Following PS-MTM treatment, no residual infectivity was detected in either cell culture-derived virus stocks or clinical samples, including extensive replicate testing and three subsequent blind passages. RT-qPCR analyses confirmed preservation and stability of detectable CSFV RNA for at least 60 days under the storage conditions evaluated, including refrigerated storage and room temperature storage for Catalonia01-derived samples. Overall, these findings demonstrate that PS-MTM eliminates detectable CSFV infectivity while preserving viral RNA for molecular diagnosis. The implementation of PS-MTM may facilitate safer handling, transport, and interlaboratory exchange of CSFV-positive samples, contributing to improved biosafety, diagnostic harmonization, and global surveillance capacity for this transboundary animal disease.