Development and Application of an Insulated Isothermal RT-PCR for On-site Detecting Nebovirus

ABSTRACT

Nebovirus (NeV) is an emerge diarrhea-causing virus in calves, the aim of this study is to establish an insulated isothermal RT-PCR(iiRT-PCR) for detecting NeV on field. Based on the RdRp sequences of NeV in GenBank database, a pair of primers and a fluorescent TaqMan probe were designed and synthesized. After optimizing the react system and condition, the iiRT-PCR method for detection of NeV was established. The iiRT-PCR assay could amplify specific fragment of NeV, without amplification of irrelevant pathogens, including bovine coronavirus, bovine norovirus, bovine rotavirus, bovine viral diarrhea virus, bovine torovirus, bovine Cryptosporidium parvum, bovine Eimeria. The intra- and inter-coefficients of variation were 3.07%-3.12% and 2.45%-3.01%, respectively, and the detection limit of viral nucleic acid of the assay was 5.38 copies•μL-1. One hundred and one calf diarrhea samples, collected from Hongyuan County, Ruoergai Prefecture, Xichang City, Liangshan Yi Autonomous Prefecture and Langzhong City in Sichuan Province during 2020-2021, were used to detect NeV, and 64.36% samples were detected as NeV positive. The study established an iiRT-PCR method for NeV detection with good specificity and reproducible as well as high sensitivity. Moreover, combined with the premixed detection reagent and PetNAD nucleic acid extraction kit, this assay could be used to NeV detect on-site, and only 1 hour from nucleic acid extraction to result report, which contribute to the fast detection for NeV.