Porcine circovirus type 3 (PCV3) is a novel circovirus that was firstly detected in the USA. PCV3 is associated with porcine dermatitis and nephropathy syndrome (PDNS), reproductive failure and cardiac and multisystemic inflammation. Latterly, PCV3 was detected in Guangxi, China. Forty-one of 108 (37.96%) samples and nine of 47 (19.14%) samples were PCV3 positive in pig farms and pig slaughter houses, respectively. Three PCV3 strains were sequenced and designated PCV3-China/GX2016-1, PCV3-China/GX2016-2 and PCV3-China/GX2016-3. The complete genome of PCV3-China/GX2016-2 and PCV3-China/GX2016-3 is both 2,000 bp in length, while PCV3-China/GX2016-1 is of 1,999 bp and has a G deletion at position of 1,155 in its genome. The complete genome and capsid nucleotide of the three PCV3 strains identified in this study shared 97.5%-99.4% and 96.7%-99.1% identities with that of the other PCV3 strains available in NCBI, respectively. Phylogenetic analysis based on complete genome and capsid gene of 35 PCV3 strains showed that the three PCV3 sequences from Guangxi Province were divided into two clusters. The results of this study contribute to the understanding of PCV3 molecular epidemiology.

More than 6,000 mosquitoes of six species from six sites were collected and tested for their virome using metagenomics sequencing and bioinformatic analysis. The identified viral sequences belonged to more than 50 viral families. The results were verified by PCR of selected viruses in all mosquitoes, followed by phylogenetic analysis. In the present study, we identified the partial dengue virus (DENV), Zika virus (ZIKV), and Japanese encephalitis virus (JEV) sequences in mosquitoes. Metagenomic analysis and the PCR amplification revealed three DENV sequences, one of which encodes a partial envelope protein. Two ZIKV sequences both encoding partial nonstructural protein 3 and one JEV sequence encoding the complete envelope protein were identified. There was variability in the viral titers of the newly isolated virus JEV-China/YN2016-1 of different passage viruses. The newly identified Zika virus gene from ZIKV-China/YN2016-1 was an Asian genotype and shared the highest nucleotide sequence identity (97.1%) with a ZIKV sequence from Thailand isolated in 2004. Phylogenetic analysis of ZIKV-China/YN2016-1 and ZIKV-China/YN2016-2 with known Flavivirus genes indicated that ZIKV has propagated in Yunnan province, China.

We collected 8,700 mosquitoes in three sites in China, which belonged to seven species. Their viromes were tested using metagenomic sequencing and bioinformatic analysis. The abundant viral sequences were detected and annotated belonging to more than 50 viral taxonomic families. The results were verified by PCR, followed by phylogenetic analysis. In the present study, we identified partial viral genes of dengue virus (DENV), a novel circovirus (CCV), densovirus (DNV), Japanese encephalitis virus (JEV), and Wuhan mosquito virus (WMV) in mosquitoes. Metagenomic analysis and PCR amplification revealed three DENV sequences, which were as homologous to the NS3 gene of DENV from Singapore isolated in 2005, with at least 91% nucleotide (nt) identity. Seven fragments of JEV encoding structural proteins were identified belonging to genotype I. They all shared high homology with structural protein genes of JEV isolated from Laos in 2009. The production of infectious virus particles of the newly isolated virus YunnanJEV2017-4 increased after passage from the BHK-21 cell line to the Vero cell line. Novel circovirus-related genes were identified and as being related to an unnamed gene of a mosquito circovirus (MCCV) sequence from the USA isolated in 2011, with at least 41% nt identity: this distant relationship suggests that the parent virus might belong to a novel circovirus genus. Additionally, numerous known viruses and some unknown viruses were also detected in mosquitoes from Yunnan province, China, which will be tested for propagation.