Molecular detection and genetic characterization of bovine hepacivirus identified in ticks collected from cattle in Harbin, northeastern China

Detection and characterization of bovine hepacivirus in cattle and sheep from Hulunbuir, northeastern China

Background

Bovine hepacivirus (BovHepV) is a recently identified member of the expanding genus Hepacivirus within the family Flaviviridae. However, the genetic diversity, geographical distribution, and host range of the virus remains poorly understood.

Methods

In this study, serum samples from cattle and sheep were obtained in Hulunbuir and pooled to establish RNA libraries, which were then analyzed using transcriptome sequencing. BovHepV-positive samples were confirmed using semi-nested PCR with primers designed based on the obtained viral sequences. Comprehensive bioinformatics analyses were employed to assess sequence similarity, phylogenetic evolution, and recombination of the obtained viral strains.

Results

A total of 988 serum samples from sheep (520) and cattle (468) were collected from 12 administrative districts in Hulunbuir from June to August, 2022. Semi-nested PCR revealed 6 BovHepV-positive districts with prevalence ranging from 2.0% to 35.0% in cattle, and one BovHepV-positive district with prevalence of 2.5% in sheep. The nucleotide sequence identities between viral strains from sheep and cattle ranged from 91.3% to 93.8%, while the amino acid sequence identities were between 95.4% and 96.7%. Phylogenetic analyses classified the obtained BovHepV strains within subtype G, genotype 1. Recombination analysis revealed the intergenerational relationships among the viral strains obtained from cattle and sheep.

Conclusion

We identified genetic diversity in subtype G strains in cattle and detected a BovHepV strain in a sheep for the first time in northeastern China, confirming cross-species transmission and co-circulation between cattle and sheep, thus expanding the virus's host range.

Two bovine hepacivirus genome sequences from U.S. cattle

Bovine hepacivirus (BoHV) is closely related to the hepatitis C virus (HCV) in humans and can cause both acute and chronic liver infections in cattle. BoHV was first identified in Ghana and Germany in 2015 and since then it has been detected and characterized in other countries around the world, but no strains have been sequenced from U.S. cattle. To date, BoHV has been classified into 2 genotypes (1 and 2), with genotype 1 being further divided into 11 subtypes (A-K). However, the true genetic diversity of BoHV is likely underestimated given limited surveillance and a lack of published genome sequences. Here, we sequenced 2 nearly complete BoHV genomes from serum samples collected in 2019 from beef cattle in Missouri. Sequence comparisons and phylogenetic analysis showed that isolate MARC/2019/60 had high sequence homology with genotype 1, subtype E isolates from China. In contrast, isolate MARC/2019/50 represented a novel BoHV subtype within genotype 2. Thus, we report the first genomic characterization of BoHV isolates from U.S. cattle, and the second complete BoHV2 genome worldwide. This work increases our knowledge of the global genetic diversity of BoHV and demonstrates the co-circulation of divergent BoHV strains in U.S. cattle.

Diversity of species and geographic distribution of tick-borne viruses in China

Introduction

Tick-borne pathogens especially viruses are continuously appearing worldwide, which have caused severe public health threats. Understanding the species, distribution and epidemiological trends of tick-borne viruses (TBVs) is essential for disease surveillance and control.

Methods

In this study, the data on TBVs and the distribution of ticks in China were collected from databases and literature. The geographic distribution of TBVs in China was mapped based on geographic locations of viruses where they were prevalent or they were detected in vector ticks. TBVs sequences were collected from The National Center for Biotechnology Information and used to structure the phylogenetic tree.

Results

Eighteen TBVs from eight genera of five families were prevalent in China. Five genera of ticks played an important role in the transmission of TBVs in China. According to phylogenetic analysis, some new viral genotypes, such as the Dabieshan tick virus (DTV) strain detected in Liaoning Province and the JMTV strain detected in Heilongjiang Province existed in China.

Discussion

TBVs were widely distributed but the specific ranges of viruses from different families still varied in China. Seven TBVs belonging to the genus Orthonairovirus of the family Nairoviridae such as Nairobi sheep disease virus (NSDV) clustered in the Xinjiang Uygur Autonomous Region (XUAR) and northeastern areas of China. All viruses of the family Phenuiviridae except Severe fever with thrombocytopenia syndrome virus (SFTSV) were novel viruses that appeared in the last few years, such as Guertu virus (GTV) and Tacheng tick virus 2 (TcTV-2). They were mainly distributed in the central plains of China. Jingmen tick virus (JMTV) was distributed in at least fourteen provinces and had been detected in more than ten species of tick such as Rhipicephalus microplus and Haemaphysalis longicornis, which had the widest distribution and the largest number of vector ticks among all TBVs. Parainfluenza virus 5 (PIV5) and Lymphatic choriomeningitis virus (LCMV) were two potential TBVs in Northeast China that could cause serious diseases in humans or animals. Ixodes persulcatus carried the highest number of TBVs, followed by Dermacentor nuttalli and H. longicornis. They could carry as many as ten TBVs. Three strains of Tick-borne encephalitis (TBEV) from Inner Mongolia Province clustered with ones from Russia, Japan and Heilongjiang Province, respectively. Several SFTSV strains from Zhejiang Province clustered with strains from Korea and Japan. Specific surveillance of dominant TBVs should be established in different areas in China.