Fast and Simplified CRISPR–Cas13d Assay for Sensitive Detection of Porcine Deltacoronavirus

Rapid and portable diagnostic technologies are essential for controlling infectious diseases. Here, we describe RAPID (Rapid Automated Portable Integrated Detection), a single-step, extraction-free CRISPR-Cas13d-based assay for sensitive and specific detection of porcine deltacoronavirus (PDCoV) RNA. RAPID integrates isothermal recombinase polymerase amplification with EsCas13d-mediated collateral cleavage in a one-pot reaction, enabling sample-to-answer detection within 30 min. A brief room-temperature lysis step allows direct RNA release from unextracted samples, simplifying sample preparation and reducing equipment requirements. Lyophilized reagents enhance stability during refrigerated storage (≤4 °C) and facilitate simplified transportation using conventional cooling measures, thereby reducing reliance on strict cold-chain logistics. The assay operates optimally at 37 °C and remains functional under ambient (∼25 °C) conditions with reduced sensitivity, permitting instrument-free operation when temperature control is unavailable. Detection is achieved via in-tube fluorescence or lateral-flow readouts. Clinical validation using porcine samples showed complete concordance with RT-qPCR, achieving 100% sensitivity and specificity. RAPID provides a practical point-of-care diagnostic platform for on-farm surveillance and deployment in resource-limited settings.