Since late 2011, pseudorabies virus (PRV; Suid herpesvirus 1) infection was widely prevalent in vaccinated swine farms in China, and caused tremendous economic losses in the swine industry. To understand the epidemic and biological characteristics of the virus, a total of 1,174 tissue samples were collected from Bartha-K61-immunized swine farms in Henan province of China between 2012 and 2019, and PRV strains were isolated and the complete sequences of gE and gC genes were amplified by PCR. The detection rate of PRV was 15.25% (179/1174), which varied from 6.61% to 25.00% between 2012 and 2019. And 16 PRV isolates were obtained, and could cause clinical symptoms and death in mice. The phylogenetic trees based on the sequences of gE and gC genes showed that the 16 PRV strains in this study at these two phylogenetic trees all clustered to a relatively independent branch altogether with the Chinese variant PRV strains (after 2012), and sequence analysis of the isolates revealed that gE and gC both contained amino acid insertions, substitutions or deletions compared with European-American PRV strains and early Chinese PRV strains (before 2012). In addition, it was the first report that eight strains (8/16) in this study harbored a unique amino acid substitution at site 280 (F to L) of gC gene. In the protection assay, the emulsion containing inactivated PRV NY isolate could provide complete protection against variant NY, and the titer of neutralizing antibodies was 1:82. This study might enrich our understanding of the evolution of variant PRVs as well as pave the way for finding a model virus to develop a novel vaccine based on PRV variants.

To investigate the epidemic profile and genetic diversity of porcine bocavirus (PBoV), 281 clinical samples including 236 intestinal tissue samples and 45 fecal samples were collected from diarrheal piglets in 37 different pig farms of central China, and two SYBR Green I-based quantitative PCR assays were developed to detect PBoV1/2 and PBoV3/4/5 respectively. The results showed the detection limits of two assays were 1.66 × 101 genome copies/μl of PBoV1/2 and 3.3 × 101 copies/µL of PBoV 3/4/5. 148 (52.67%) of the 281 clinical samples were positive for PBoV1/2, 117 (41.63%) were positive for PBoV3/4/5, 55 (19.57%) were positive for both PBoV1/2 and PBoV3/4/5, and 86.49% (32/37) of the pig farms were positive for PBoV. Subsequently, complete genomic sequences of two PBoV strains (designated CH/HNZM and PBoV-TY) from two different farms were sequenced. The phylogenetic analysis demonstrated that the two PBoV strains obtained in this study belonged to the PBoV2 group and had a close relationship with other 12 PBoV2 strains, but differed genetically from PBoV1, PBoV3/4/5 and 7 other bocaviruses. CH/HNZM and PBoV-TY were closely related to the PBoV strain GD18 (KJ755666) which may be derived from PBoV strains 0912/2012 (MH558677) and 57AT-HU (KF206160) through the recombination analysis. Compared with reference strain ZJD (HM053694)-China, a higher amino acid variation was found in the NS1 protein of CH/HNZM and PBoV-TY. These results extend our understanding of the molecular epidemiology and evolution of PBoV.

To investigate the phylogenetic and evolutionary analysis of porcine bocavirus (PBoV), 281 clinical samples including 236 intestinal tissue samples and 45 fecal samples were collected from diarrheal piglets in 27 different pig farms of central China, and SYBR Green I-based qPCR assays were developed to detect PBoVs. Among the 281 samples, 148 (52.67%) were positive for PBoV1/2, 117 (41.63%) were positive for PBoV3/4/5, and 55 (19.57%) were positive for both PBoV1/2 and PBoV3/4/5. Subsequently, two complete genome sequences of PBoV strains CH/HNZM (accession numbers KX017193) and PBoV-TY (accession numbers MH454686) were cloned in this study. A multiple genomic sequence alignment showed that the pairwise similarity of the two PBoV strains was 94.8%, and they had 44.5%-95.8% genomic nucleotide sequence identity with 35 reference strains. The phylogenetic analysis demonstrated that the two PBoV strains CH/HNZM and PBoV-TY clustered into the PBoV2 group, and PBoV-TY was closely related to the PBoV strain GD18 strain (KJ755666) which may be derived from PBoV strains 0912/2012 (MH558677) and 57AT-HU (KF206160) through the recombination analysis. Compared with reference strain ZJD (HM053694)-China, a higher variation in the NS1 amino acids of PBoVs was found for CH/HNZM and PBoV-TY. These results had provided further information of the PBoV prevalence in central China, and they extend our understanding of the molecular epidemiology and evolution of PBoV.