1 INTRODUCTION
Bocavirus is a novel classified genus which belongs to the family Parvoviridae , subfamily Parvovirinae , and includes human bocavirus (HBoV), porcine bocavirus (PBoV), canine minute virus (CMV), bovine bocavirus (BPV), gorillas bocavirus (GBoV), and California sea lion bocavirus (CslBoV) (Lau et al., 2008; Li et al., 2011). In 2009, porcine boca-like virus (PBo-likeV) was first reported from lymph nodes of pigs with post-weaning multi-systemic wasting syndrome (PMWS) in Sweden (Blomstrom et al., 2009). PBo-likeV was subsequently discovered in China and named as porcine bocavirus (PBoV) or PBoV1 in 2010 (Zhai et al., 2010). Since then, PBoV has been identified in Europe, Asia, North America and Africa (Zhou et al., 2014).
PBoV is a non-enveloped single-stranded DNA virus which consists of three open reading frames (ORFs), ORF1, ORF2, and ORF3 (Arthur et al., 2009). ORF1 encodes a nonstructural protein 1 (NS1 ), ORF2 encodes viral caspid proteins 1 and 2 (VP1/2 ), and VP1 consists of the entire VP2 sequence and an additional N-terminal region (Sun et al., 2009), ORF3 encodes nuclear phosphoprotein 1(NP1 ). Based on the VP 1 and VP 2 sequences, PBoV has been classified into different clades, which includes PBoV1, PBoV2, PBoV3, PBoV4, PBoV5, PBoV3C, PBoV-6V and PBoV-7V. And PBoV was proposed to be classified into three different groups, PBoV G1, PBoV G2, and PBoV G3 (Zhou et al., 2014).
To date, pigs infected with PBoV have been reported in 20 provinces or regions in China with the prevalence between 7.3% and 64% (Wang et al., 2014; Zhang et al., 2015; Zhou et al., 2018). Co-infection of PBoV with other porcine viruses has also been reported, such as porcine epidemic diarrhea virus (PEDV), porcine circovirus type 2 (PCV2), pseudorabies virus (PRV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine torque teno virus (PTTV) and classic swine fever virus (CSFV) (Blomstrom et al., 2010; McMenamy et al., 2013; Zhang et al., 2014; Huang et al., 2014; Zhou et al., 2014; Luo et al., 2015). In addition, PBoV has a significantly higher infection rate in diseased pigs than in healthy pigs, and the co-infection rate of PEDV and PBoV was higher in samples of diarrheal pigs than that of healthy pigs, suggesting that the PBoV might play an important role in causing diarrhea in piglets (Zhai et al., 2010). However, the pathogenicity of PBoV needs further recognized. In the current study, we aimed to investigate the PBoV prevalence in diarrheal pigs and analyze full-length genome sequence properties of PBoV from central China.