title: Swine hepatitis E virus strains in Japan form four phylogenetic clusters comparable with those of Japanese isolates of human hepatitis E virus.
abstract: Japanese patients with sporadic acute hepatitis E are infected with polyphyletic strains of hepatitis E virus (HEV). Hepatitis E is considered a zoonotic disease. Thus far in Japan, only three strains of swine HEV have been identified and an antibody study for HEV antibodies has not been done on Japanese pigs. To determine the prevalence of swine HEV infection in Japan and the extent of genetic variation among Japanese swine HEV strains, we tested serum samples obtained from 2500 pigs from 2 to 6 months of age at 25 commercial swine farms in Japan for the presence of IgG antibodies to HEV and swine HEV RNA. Anti-HEV antibodies were detected in 1448 pigs (58 %). One-hundred-and-thirteen (15 %) of the 750 3-month-old pigs and 24 (13 %) of the 180 4-month-old pigs were positive for swine HEV RNA. The nucleotide sequence of a 412 bp region within open reading frame 2 of the 137 swine HEV isolates was determined. Sequence analyses revealed that the 137 isolates shared 76.6-100 % nucleotide sequence identities and were classifiable into genotype III (93 %) or IV (7 %) and that the isolates from the same farm were > or = 97.1 % similar to each other. Phylogenetic analysis showed that the Japanese swine and human HEV isolates segregated into four clusters, with the highest nucleotide identity being 94.4-100 % between swine and human isolates in each cluster. These results indicate that swine HEV is widespread in the Japanese swine population and further support the hypothesis that swine serve as reservoirs for HEV infection.
authors.affiliation: Immunology Division and Division of Molecular Virology, Jichi Medical School, Tochigi-Ken 329-0498, Japan.
authors.forename: Masaharu
authors.initials: M
authors.lastname: Takahashi
authors.affiliation: Immunology Division and Division of Molecular Virology, Jichi Medical School, Tochigi-Ken 329-0498, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Nishizawa
authors.affiliation: Japanese Red Cross Saitama Blood Center, Saitama-Ken 338-0001, Japan.
authors.forename: Haruko
authors.initials: H
authors.lastname: Miyajima
authors.affiliation: Japanese Red Cross Saitama Blood Center, Saitama-Ken 338-0001, Japan.
authors.forename: Yuhko
authors.initials: Y
authors.lastname: Gotanda
authors.affiliation: Institute of Swine Industry, Ibaraki Prefectural Livestock Research Center, Ibaraki-Ken 300-0508, Japan.
authors.forename: Teruhiko
authors.initials: T
authors.lastname: Iita
authors.affiliation: Department of Medical Sciences, Toshiba General Hospital, Tokyo 140-8522, Japan.
authors.forename: Fumio
authors.initials: F
authors.lastname: Tsuda
authors.affiliation: Immunology Division and Division of Molecular Virology, Jichi Medical School, Tochigi-Ken 329-0498, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Okamoto
mesh_terms: D000818:Animals; D001483:Base Sequence; D004197:Disease Reservoirs / Q000662:veterinary*; D005838:Genotype; D006508:Hepatitis Antibodies / Q000097:blood; D016751:Hepatitis E / Q000097:blood / Q000453:epidemiology / Q000662:veterinary*; D016752:Hepatitis E virus / Q000145:classification / Q000276:immunology / Q000302:isolation & purification*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007564:Japan / Q000453:epidemiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D012367:RNA, Viral / Q000032:analysis; D017423:Sequence Analysis, RNA; D016036:Seroepidemiologic Studies; D013552:Swine / Q000821:virology*; D013553:Swine Diseases / Q000097:blood / Q000453:epidemiology* / Q000821:virology
chemical_list: D006508:Hepatitis Antibodies; D007074:Immunoglobulin G; D012367:RNA, Viral