Identification and characterization of a novel subgenotype of bovine viral diarrhea virus isolated from dairy cattle in Northwestern China

Abstract

Bovine viral diarrhea virus (BVDV) was detected by RT-PCR in 105 out of 391 samples which were collected from five dairy farms in Ningxia, China during 2010–2011. Non-cytopathogenic BVDV was isolated from 13 samples and a 230-bp fragment of the 5′-untranslated region was amplified and sequenced. While the predominant subgenotypes were BVDV-1b and BVDV-1d, a potentially novel subgenotype was identified by phylogenetic analysis, which may have implications for vaccine development.

Bovine viral diarrhea virus (BVDV) is a ubiquitous pathogen that infects domestic animals such as cattle, goats, sheep, and pigs, as well as many wild and captive animals [1]. To date, the BVDV circulating in the Chinese cattle population is mainly BVDV-1b, -1c, -1m, -1p, and BVDV-2a [2–4]. To investigate the prevalence of BVDV in Ningxia Hui Autonomous Region of China, a total of 391 blood samples were collected from five dairy farms, without vaccination history, during 2010–2011, and tested by an RT-PCR method targeting the 5′-untranslated region (5′-UTR).

One hundred and five samples were found positive for BVDV infection. Virus isolation was successful in 13 samples and all isolated viruses were of non-cytopathogenic biotype. Comparative analysis of the 230-bp fragment of the 5′-UTR showed that the 13 isolates shared an identity of 85.2–100 % and had an identity of 85.7–99.6 % between the isolates and BVDV-1 reference strains. The newly determined sequences have been deposited in GenBank under accession numbers JX437146-JX437158. Phylogenetic analysis clustered the 13 isolates into three subgenotypes: BVDV-1b, BVDV-1d, and a potentially novel subgenotype, tentatively designated as “BVDV-1*” (Fig. 1). While BVDV normally causes subclinical infection or mild disease, the cattle which were infected with “BVDV-1*” were characterized by fevers and oral lesions. Further studies are required to confirm an association between these clinical signs and BVDV-1*. This is the first report describing the detection of subgenotypes BVDV-1d and BVDV-1* in the Chinese cattle population, which may have important implications for developing effective BVDV vaccines against the newly identified subgenotypes in China.

Fig. 1

The phylogenetic tree was generated based on comparison of nucleotide sequences of the 5′-UTR of 13 BVDV isolates with sequences downloaded from the GenBank database. The tree was constructed by the neighbor-joining (NJ) method and a bootstrap test by means of MEGA version 4.1. The numbers at the phylogenetic branches indicate the bootstrap values (1,000 replicates) in percentage supporting each group. Subgenotype BVDV-1b included three isolates and is indicated in red; subgenotype BVDV-1d included six isolates and is indicated in light blue; subgenotype BVDV-1* included four isolates and is indicated in green (Color figure online)