Epizootiological surveillance of porcine circoviruses in free-ranging wild boars in China.

Four species of porcine circoviruses (PCV1-4) have been reported to circulate in Chinese domestic pigs, while the epizootiology of these viruses in free-ranging wild boars in China remains unknown. In this study, tissue and serum samples collected from diseased or apparently healthy wild boars between 2018 and 2020 in 19 regions of China were tested for the prevalence of PCV1-4 infections. Positive rates of PCV1, PCV2, and PCV3 DNA in the tissue samples of Chinese wild boars were 1.6% (4/247), 58.3% (144/247), and 10.9% (27/247) respectively, with none positive for PCV4. Sequence analysis of viral genome showed that the four PCV1 strains distributed in Hunan and Inner Mongolia shared 97.5%-99.6% sequence identity with global distributed reference strains. Comparison of the ORF2 gene sequences showed that 80 PCV2 strains widely distributed in 18 regions shared 79.5%-100% sequence identity with reference strains from domestic pigs and wild boars, and were grouped into PCV2a (7), PCV2b (31) and PCV2d (42). For PCV3, 17 sequenced strains shared 97.2%-100% nucleotide identity at the genomic level and could be divided into PCV3a (3), PCV3b (2) and PCV3c (12) based on the phylogeny of ORF2 gene sequences. Serological data revealed antibody positive rates against PCV1 and PCV2 of 11.4% (19/167) and 53.9% (90/167) respectively. The data obtained in this study improved our understanding about the epidemiological situations of PCVs infection in free-ranging wild boars in China and will be valuable for the prevention and control of diseases caused by PCVs infection.

Genetic characterization of hepatitis E virus from wild boar in China.

Hepatitis E virus (HEV), the causative agent of hepatitis E (HE), is classified into four major genotypes (1-4), with wild boar being the main natural reservoir for genotypes 3 and 4. However, little is known about the prevalence of HEV infection in wild boars in China. In this study, RT-nested PCR and RT-quantitative PCR were used to detect the HEV RNA in tissue samples taken from 331 free-ranging wild boars collected between 2018 and 2020 from 24 regions across China, and the partial ORF2 genes or complete genomes of the positive samples were sequenced. Furthermore, antibodies against HEV in 216 serum samples from wild boars were tested by ELISA. As a result, HEV RNA was detected in nine out of 331 liver samples of wild boars (2.72%), which were distributed in eight regions. Genetic and evolutionary analysis of partial ORF2 sequences indicated that the HEV strains identified in this study share 83.9%-100% nucleotide sequence identity and belong to subtypes 4d (n = 6), 4g (n = 2), and 4h (n = 1), and similar phylogeny was obtained using the complete genome sequences of seven wild boar HEV strains. Additionally, the HEV viral loads were higher in the liver than in other tissues and blood. Moreover, 61 out of 216 sera (28.2%) from wild boars tested positive for anti-HEV antibodies. To our knowledge, this is the first study to report the epidemiological situations of HEV infections in free-ranging wild boars in China, and the obtained data are valuable for prevention and control of HE.