I. Di Bartolo, Francesco Tolari, L. Del Chiaro, Andrea Caprioli, Fabio Ostanello, Francesca Martelli, Franco Maria Ruggeri, Caprioli A., Martelli F., Ostanello F., Di Bartolo I., Ruggeri F.M., Del Chiaro L., and Tolari F.
HEPATITIS E is a public health concern in many developing countries, where it is primarily transmitted by the faecal-oral route through contaminated water and food (Emerson and Purcell 2003). The disease is caused by a small, non-enveloped single-stranded RNA virus classified as the separate genus Hepevirus. Although hepatitis E disease occurs only sporadically in countries with good health care systems, the seroprevalence in healthy individuals can be high (Emerson and Purcell 2003). Porcine hepatitis E virus (HEV) is not pathogenic to general pig populations, but there is evidence that the virus may be a zoonotic agent and that animal reservoirs may exist. Experimental interspecies transmission of HEV between non-human primates and pigs has been demonstrated (Meng and others 1998), and seroepidemiological studies have shown that pig handlers are at higher risk of HEV infection than the general population (Meng and others 2002). In Japan, studies have supported the possibility of zoonotic transmission, as consumption of undercooked pig organs or meat and, in one case, of deer meat, was closely linked to cases of hepatitis E in human beings (Tei and others 2003, Yazaki and others 2003). The first porcine strain of HEV was characterised in the USA in 1997 (Meng and others 1997). Since then, several other porcine strains have been described worldwide. In the past few years, sporadic cases of autochthonous hepatitis E in human beings have been reported in several European countries, including Italy (Zanetti and others 1999). In many of these cases, the infecting HEV strain showed a high degree of homology with porcine strains of HEV detected in the same country (van der Poel and others 2001, Clemente-Casares and others 2003, Banks and others 2004a). In recent years in Europe, HEV in pig herds has been reported only in Spain (Clemente-Casares and others 2003), the UK (Banks and others 2004b) and the Netherlands (van der Poel and others 2001). This short communication describes the detection, by a nested reverse transcriptase-PCR (nested RT-PCR), of HEV in two Italian pig farms, and the phylogenetic analysis of the viral strains. Thirty-four faecal and 22 serum samples were collected from five different farrow-to-finish farms located in northcentral Italy. Samples were collected from healthy pigs between two and five months of age. Faecal samples represented pools of faeces from animals of the same age group. Total RNA was extracted from 140 μl of faecal suspension or serum using a QIAmp viral RNA kit (Qiagen), according to the manufacturer’s instructions. Template cDNA was reverse transcribed using random hexamers, according to standard protocols. A 145 base pair (bp) fragment of the open reading frame 2 of HEV was amplified from the prepared cDNA by nested PCR, as described by Erker and others (1999). A faecal suspension from a human patient with hepatitis E was used as a positive control. Nested RT-PCR products were visualised on 2 per cent agarose gel, and bands of the correct size were excised and purified with the QIAquick Gel Extraction Kit (Qiagen). Nucleotide sequencing was performed using the ABI PRISM BigDye Terminator kit, version 2·0 (Applied Biosystems). Sequences were assembled with SEQMAN (DNASTAR), and alignment was performed using the ClustalX algorithm. The HEV genome was detected in two faecal pools (5·9 per cent) collected at two different farms, but all the serum samples were negative. The positive faecal pools were obtained from groups of pigs aged 4·5 and 2·5 months, respectively. Phylogenetic analysis of the two viral sequences (113 bp), termed HEVBO/01 and HEVPI/01, was performed by the neighbour-joining method using PHYLIP 3·6. Bootstrap confidence values (500 replicates) were calculated by using the Seqboot and Consense programs. A phylogenetic tree (Fig 1) was created with the Treeview software using an avian HEV isolate as out group. Phylogenetic analysis of the viral sequences showed that the two Italian strains, HEVBO/01 and HEVPI/01, belonged to genotype 3, as did other porcine and human HEV strains indigenous to Europe. However, they differed significantly from each other, being only 84 per cent identical (18 nucleotide changes). The two Italian strains clustered with strains from countries where HEV is considered non-endemic. In particular, HEVPI/01 was related (with 90 per cent identity) to a human strain (AY540113) detected in a sporadic case of acute autochthonous hepatitis E in Spain (Buti and others 2004). In conclusion, this report represents the first description of HEV in Italian pig herds, and confirms the presence of the virus in apparently healthy pigs. These findings are important, because of the potential risk of transmission of porcine HEV to human beings, either by contact with infected pigs or by ingestion of contaminated undercooked meat. However, further studies are needed to address the true zoonotic potential of HEV in pigs. Studies are in progress to evaluate the prevalence of the infection in Italian pigs. The study of a high number of viral strains will be necessary to assess intraspecies and interspecies HEV homologies and to understand whether zoonotic transmission of HEV may occur in Italy.