Evaluation of an incubation instrument-free reverse transcription recombinase polymerase amplification assay for rapid and point-of-need detection of canine distemper virus

Canine distemper, caused by Canine distemper virus (CDV), is a highly contagious and fatal systemic disease in free-living and captive carnivores worldwide. Accurate, rapid and simple detection of CDV is critical to improve disease management and prevent outbreaks. In this study, a visible and incubation instrument-free reverse-transcription recombinase polymerase amplification assay combined with lateral flow strip (LFS RT-RPA) was developed to detect CDV using primers and lateral flow (LF) probe specific for the nucleocapsid (N) protein gene. The CDV LFS RT-RPA assay was performed in a closed fist using body heat for 15 min, and the products were visible to the naked eyes on the LFS within 5 min. The assay could detect CDV, and there was no cross-reaction with the other viruses tested. Using the in vitro transcribed CDV RNA as template, the analytical sensitivity was 9.4 × 101 copies per reaction, which was the same result as that of a real-time RT-PCR. The assay performance was further evaluated by testing 32 nasal/oropharyngeal swab samples, and CDV RNA positive rate was 62.0% (20/32) by LFS RT-RPA, which was the same result as that of the real-time RT-PCR assay. The performance of the LFS RT-RPA was comparable to real-time RT-PCR, while the LFS RT-RPA assay was much faster and easier to perform. The novel CDV LFS RT-RPA assay provides an attractive and promising tool for rapid and reliable detection of CDV in the underequipped laboratory and point-of-need facility, which is of great significance in CD control in low resource settings.