Development of an RPA-CRISPR-Cas12a Fluorescence Assay for Rapid and Sensitive Detection of Tilapia Parvovirus (TiPV).

Tilapia parvovirus (TiPV) is an emerging pathogen associated with high mortality rates in farmed tilapia, highlighting the urgent need for rapid and accurate diagnostic tools. In this study, we established an RPA-CRISPR/Cas12a detection system targeting the TiPV NS1 gene. The assay conditions were systematically optimised, including 15-min RPA amplification at 39°C, with reagent concentrations of 200 nM Cas12a, 250 nM crRNA and 200 nM ssDNA reporter. Specificity tests showed no cross-reactivity with other tilapia pathogens (TiLV, S. agalactiae) and other aquatic pathogens (LMBRaV, YcCV, GCRV II, WSSV, CyHV-2, SVCV). Sensitivity evaluation revealed a limit of detection (LoD) of 1.97 × 101copies/μL, which was 100-fold more sensitive than PCR (1.97 × 103copies/μL). Clinical validation with 20 tilapia samples demonstrated a 50% positive detection rate for RPA-CRISPR/Cas12a, 15% higher than PCR (35%). This integrated method combines the advantages of RPA and CRISPR-based signal transduction, offering a field-applicable solution for TiPV monitoring in resource-limited aquaculture environments.