Recombinase polymerase amplification-lateral flow dipstick (RPA-LFD) designed for rapid detection of canine distemper virus

In the present study, recombinase polymerase amplification (RPA) was combined with the colloidal gold lateral flow dipstick (LFD) method to establish a new, stable, and efficient assay for the detection of canine distemper virus (CDV). We designed a set of specific primers labeled with biotin and a specific probe labeled with dSpacer and C3 spacer, according to the conserved region in the N-terminal gene sequence of CDV. The reaction conditions and systems were then optimized, and the sensitivity and specificity were analyzed for potential clinical application. The results showed that the RPA-LFD assay for CDV detection was successfully established. We also found that the temperature in a closed fist (35°C) is optimal for the RPA reaction. The optimal ratio of primer to probe was 2:1. The minimum detection limit of the RPA-LFD assay was 1 × 10¹ the median tissue culture infective dose (TCID₅₀)/mL. Using this assay with samples from experimentally infected dogs, CDV was detected in nasal secretions, eye secretions, and blood on the fourth day post infection. In summary, this novel RPA-LFD assay for CDV detection is simple to use, and preliminary findings indicate its high specificity and sensitivity.