Molecular detection and genotyping of bovine viral diarrhea virus in Western China

Abstract

Background: Bovine viral diarrhea virus (BVDV) is an important global viral pathogen of cattle and other ruminants. To survey the infection rate and genetic diversity of BVDV in western China, a total of 1234 serum samples from 17 herds of dairy cattle, beef cattle and yak in 4 provinces were collected in 2019.

Results: All the 1234 serum samples were screened individually for BVDV by RT-PCR. Our results demonstrated that the average positive rate of BVDV was 7.2% (89/1234) in animals and 82.4% (14/17) in herds. Thirteen BVDV strains were isolated from RT-PCR positive clinical samples and they were all NCP biotype. BVDV-1a and 1c subgenotypes were identified from 22 selected virus isolates in 14 BVDV-positive herds. These results confirmed that BVDV-1a and BVDV-1c were circulating in western China, similar to the BVDV epidemics in cattle in other regions of China.

Conclusions: This study provides data for monitoring and vaccination strategies of BVDV in western China.

Keywords: BVDV; Bovine; Genotype; RT-PCR; Western China.

Fig. 1

The isolated BVDV strains were confirmed by immunofluorescence, RT-PCR and transmission electron microscope, respectively. a BVDV-infected (a-c) or negative control MDBK cells (d-f) were examined by immunofluorescence using polyclonal antibodies against BVDV E2 protein. b The typical viral particles in the cytoplasm of infected MDBK cell(g, red arrow). The viral particles were measured approximately 60 nm in diameter and occurred as clusters inside vesicles(h, red arrow). c The BVDV strains were detected by 5’UTR RT-PCR (201 bp). Representative electron microscopic image of field BVDV isolates (i). lane M:weight size marker (2000 bp,1000 bp, 750 bp, 500 bp, 250 bp,100 bp), lane 1: positive control; lane 2: negative control, lanes 3–7: BVDV strains isolated from clinical serum samples

Fig. 2

Phylogenetic analysis based on 5’UTR sequence. A phylogenetic tree of the 5’UTR was created using the 5’UTR sequences of 22 selected BVDV isolates and 57 reference isolates retrieved from the GenBank database. ●BVDV isolates identified in provinces of Shaanxi (green dot), Ningxia (red dot), Xinjiang (yellow dot) and Tibet (blue dot) in this study.14 isolates were clustered in BVDV-1a (frame) and 8 isolates clustered in BVDV-1c (frame)