Antibody detection and genotyping of bovine viral diarrhea virus in the dairy farms in Ningxia, China.

Bovine viral diarrhea/mucosal disease (BVD/MD) is a viral infectious disease which brings serious harm to the cows. There were only reports on bovine viral diarrhea virus (BVDV) infected dairy cows in Ningxia Province, China with no BVDV typing being reported. The purpose of this study is to evaluate the prevalence and distribution of BVD in Ningxia and to analyze the diversity of the subtype genes of BVDV. The enzyme-linked immunosorbent assay (ELISA) was used to detect 1,890 blood samples from 13 dairy farms in 7 cities of Ningxia. The N-gene of 49 antigen positive samples were amplified by reverse transcription polymerase chain reaction (RT-PCR). Mega 7.0 software was used to construct phylogenetic tree and analyze the classification status of the virus strains. The antibody positive rate remained in the range of 88.15 - 100% with an average rate of 92.59%. The antigen positive rate was from 1.11 to 4.44%. The confirmed subtypes of BVDV include BVDV-1a, BVDV-1d, BVDV-1m, BVDV-1q, and BVDV-2a, which agree with the commonly seen subtypes in China. However, our study identified BVDV-1a, BVDV-1m, and BVDV-2a virus strains for the first time in Ningxia, which indicate the complexity of genetic diversity of BVDV in Ningxia. In conclusion, we conducted the first genotyping of BVDV in Ningxia, which sets a solid foundation for further study of the law of change and emergence mechanism of the subtypes of BVDV virus strains in Ningxia and China. [ABSTRACT FROM AUTHOR]