Molecular characterisation and phylogenesis of swine hepatitis e virus (HEV) strains identified in italy

Hepatitis E (HE), caused by hepatitis E virus (HEV), is an infectious disease that in humans shows clinical and morphological features of acute hepatitis. HE represents an important public health problem in developing countries, but in recent years, a number of sporadic cases have also been described in industrialised countries, Italy included. Increasing evidence supports the hypothesis that HE is an emerging zoonotic disease, and that pigs are the main animal reservoir of the infection. HEV is divided into 4 major genotypes, which differ with respect to geographic distribution, host range and pattern of infection. Genotypes 3 and 4 have a wide animal host range and also infect humans. Recently a new classification into subtypes has been proposed, and genotypes 3 and 4 have been further divided into 10 and 7 subtypes respectively. The aims of this study were the molecular characterization of some HEV strains identified in pigs from 45 different Italian herds, and the analysis of their correlation with other European strains of human and pig origin. Bile samples collected from 137 randomly selected pigs of 2-4 months of age from 45 different Italian pig herds were tested for HEV RNA. Samples were examined by nested-RT-PCR using degenerate primers annealing the ORF2 capsid region. 15 randomly selected positive samples were sequenced using ABI PRISM BigDye Terminator Kit 2.0 (Applied Biosystems) and aligned with other strains present in the NCBI Data Bank using DNASIS Max software (Hitachisoft). The phylogenetic analysis was carried out with the Bionumerics software, and the dendrogram was obtained with the UPGMA method. All 15 HEV strains identified belonged to genotype 3. Genomic identity of the strains analysed ranged between 80.4% and 99.6%. Compared with other European strains, samples 122, 127 and 88 had a high percentage of identity (92.5%) with a swine Dutch strain belonging to subtype 3c. Sample 87 had a nucleotide identity of 92.8% with a Spanish human strain of subtype 3f, while sample 85 had 88.7% identity with a UK swine strain belonging to subtype 3e. To date, genotype 3 is the only genotype identified in swine in Europe. In our study three different genotype 3 lineages containing sequences similar to subtype G3f, G3c and G3e were identified. Subtypes 3e and 3f have been demonstrated to be common in European countries, while subtype 3c may represent a local strain circulating in the Netherlands. Further studies will be necessary to investigate the characteristics and molecular epidemiology of swine genotype 3 subtypes evolving in Europe.