HEV circulating in pig populations in Italy since 2000

Hepatitis E Virus (HEV) is the causative agent of human hepatitis E. Swine are the main asymptomatic reservoir of genotype 3 and 4, which circulate in industrialized area and can be transmitted zoonotically. In Italy, the first autochthonous human case of hepatitis E associated with genotype 3 HEV was detected in 1999, whereas the first HEV (SwHEV) genotype 3 strain in pigs was reported in 2006. In our study, we investigated HEV presence in Italian pig farms one year after the first report of autochthonous case of hepatitis E in humans. In fact, we analyzed fecal samples from 78 (63 fatteners and 15 breeders) animals collected in 2000 from 3 pig farms in Northern Italy. Total RNA was extracted and subject to retrotranscription followed by PCR. Three different genome regions were amplified: Capsid, RNA–dependent RNApolymerase (RdRp) and Methyltrasferase (Met). Positive amplicons were sequenced and analyzed by Bionumerics. Overall, 15/78 (19.23%) fecal samples tested positive for SwHEV genome detection by RTPCR amplifying a capsid fragment. Only 12 and 9 out of 15 capsid-positive samples were further confirmed by PCRs amplifying the RdRp and Met fragments, respectively. All HEV positive animals belong to fatteners, except for one sow. Furthermore, 2 of 3 farms were positive for HEV presence. Sequence analysis confirmed the presence of HEV genotype 3 subtype e in all positive samples in both farms. All strains showed a nucleotide identity ranging between 92.5% to 100% depending on the region considered. It should be noted that subtype e was rarely identified in Italy if compared with subtypes f, h and c. We can speculate that, over the years, some viral variants were better adapted than others in swine population. Moreover, we compared sequences obtained in this study with 41 European and non-European strains identified in humans and swine, deposited in NCBI since 1993. Sequence analysis showed high nucleotide identity (89-94%) between strains identified in different years for the 3 genome regions examined, suggesting great stability of the HEV genome. Our analysis was not able to find a strict relation between Italian swine and human strains.