Rapid detection of bovine rotavirus a by isothermal reverse transcription recombinase polymerase amplification assays

Bovine rotavirus A (BRVA) is considered to be the most common pathogen of severe diarrhea in cattle worldwide, which could lead to the death of newborn calves and cause the significant economic losses to the cattle industry. As a novel isothermal nucleic acid amplification technique, recombinase polymerase amplification (RPA) has been applied widely for the rapid detection of different important pathogens in human and animals.

An RT-RPA assay based on the real time fluorescence monitoring (real-time RT-RPA) and an RT-RPA assay combined with a lateral flow strip (LFS RT-RPA) were successfully developed by targeting the VP6 gene of BRVA. The RT-RPA assays allowed the exponential amplification of the target fragment in 20 min. After incubation of the LFS RT-RPA on a metal bath at 40 °C, the results were displayed on the lateral flow strip within 5 min, while real-time RT-RPA allowed the real-time observation of the results in Genie III at 42 °C. Both of the two assays showed high specificity for BRVA without any cross-reaction with the other tested pathogens causing diarrhea in cattle. With the standard RNA of BRVA serving as a template, the limit of detection for real-time RT-RPA and LFS RT-RPA were 1.4 × 10² copies per reaction and 1.4 × 10¹ copies per reaction, respectively. In the 134 fecal samples collected from cattle with diarrhea, the BRVA positive rate were 45.52% (61/134) and 46.27% (62/134) in real-time RT-RPA and LFS RT-RPA, respectively. Compared to a previously published real-time PCR, the real-time RT-RPA and LFS RT-RPA showed a diagnostic specificity of 100%, diagnostic sensitivity of 98.39% and 100%, and a kappa coefficient of 0.985 and 1.0, respectively.

In this study, BRVA was successfully detected in cattle fecal samples by the developed real-time RT-RPA and LFS RT-RPA assays. The developed RT-RPA assays had great potential for the rapid detection of BRVA in under-equipped diagnostic laboratory and the point-of-need diagnosis at quarantine stations and farms, which is of great importance to control BRVA-associated diarrhea in cattle herds.