Prevalence of hepatitis E virus and porcine caliciviruses in pig farms of Guizhou province, China

Abstract

Background: Hepatitis E virus (HEV) and caliciviruses are enteric pathogens of humans and animals, and pigs have been considered an important reservoir of these viruses.

Objectives: The aim of this study is to determine the infection rates of HEV and caliciviruses (sapovirus [SaV] and norovirus [NoV]) in different age groups of pigs in Guizhou province, China, and characterize the strains that are prevalent in this mountainous area.

Materials and methods: A total of 209 stool samples from healthy pigs of different ages were collected from 6 pig farms in Guizhou province from May to June 2009 and tested for HEV, SaV, and NoV by reverse-transcription polymerase chain reaction (RT-PCR).

Results: The overall prevalence of porcine HEV and porcine SaV was 6.7% (15/209) and 1.0% (2/209), respectively. No NoV was detected. The prevalence rates of porcine HEV infection were 15.4% in piglets aged < 1 mon (4/26), 6.8% in piglets aged between 1 and 4 mon (3/44), 12.5% in piglets aged ≈ 4 mon (6/48), and 1.1% in sows aged between 6 and 14 mon (2/91). Porcine SaV was detected only in piglets (7.7%, 2/26). All 10 HEV isolates belonged to genotype 4, clustering with a human HEV strain (AF103940) from an adjacent province.

Conclusions: This is the first report on the existence of porcine SaV in swine in Guizhou province, China. The clustering of the porcine HEV isolates with a human strain suggests cross-species transmission between swine and humans in this area.

Keywords: Caliciviruses; Genetic diversity; Hepatitis E virus; Porcine.

Figure 1

PCR products for HEV and SaV. Lane 1 to lane 6: negative control for HEV, negative control for SaV, positive control for HEV, HEV-positive sample, positive control for SaV, SaV-positive sample

Figure 2

Neighbor-joining tree of the phylogenetic relationship between HEV strainss based on a 304-nt fragment of ORF2. Bootstrap values, expressed as percentages of 1000 replications, are given at the branch point. The 10 newly identified HEV strains

Figure 3

Neighbor-joining tree of the phylogenetic relationship between SaV strains based on a 309-nt fragment of the RNA-dependent RNA polymerase gene. Bootstrap values, expressed as percentages of 1000 replications, are given at the branch points. Genbank accession numbers for the reference strains are marked at each branch points. The 2 newly identified SaV strains (Genbank accession numbers: HQ292717 for C28/CH; HQ292716 for F6/CH) are marked by filled triangles, and other Chinese SaV strains are marked by unfilled triangles.