title: Continuity and change of Japanese encephalitis virus in Toyama Prefecture, Japan.
abstract: To determine the mechanisms of maintenance and evolution of Japanese encephalitis virus (JEV) in a temperate zone, we attempted to isolate JEV from mosquitoes and pigs in Toyama Prefecture, Japan. A total of 87 JEVs were isolated from female Culex tritaeniorhynchus mosquitoes and pigs during 2005-2009. The prevalence of JEV in Toyama Prefecture was seasonally late in comparison with that of the virus during 1966-1972. Furthermore, JEVs were isolated after the peak in the number of female Cx. tritaeniorhynchus. Among JEV strains isolated in this study, two distinct groups were observed within genotype I of the phylogeny generated from nucleotide sequence information derived from the envelope and capsid/premembrane genes: strains belonging to the major type were isolated during 2005-2009, and strains from the minor type were isolated only in 2007. The major type has exhibited gradual change in its envelope and capsid/premembrane genes, and all isolates obtained in 2008 and 2009 had a novel deletion of seven nucleotides in the variable region of the 3'-untranslated region.
authors.affiliation: Toyama Institute of Health, 17-1 Nakataikoyama, Imizu, Toyama, Japan. mayumi.obara@pref.toyama.lg.jp
authors.forename: Mayumi
authors.initials: M
authors.lastname: Obara
authors.forename: Takeo
authors.initials: T
authors.lastname: Yamauchi
authors.forename: Mamoru
authors.initials: M
authors.lastname: Watanabe
authors.forename: Sumiyo
authors.initials: S
authors.lastname: Hasegawa
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Ueda
authors.forename: Kentaro
authors.initials: K
authors.lastname: Matsuno
authors.forename: Masae
authors.initials: M
authors.lastname: Iwai
authors.forename: Eiji
authors.initials: E
authors.lastname: Horimoto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kurata
authors.forename: Takenori
authors.initials: T
authors.lastname: Takizawa
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kariwa
authors.forename: Ikuo
authors.initials: I
authors.lastname: Takashima
mesh_terms: D000818:Animals; D003465:Culex / Q000821:virology*; D004664:Encephalitis Virus, Japanese / Q000145:classification / Q000302:isolation & purification*; D005260:Female; D007564:Japan; D010802:Phylogeny; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012621:Seasons; D013552:Swine / Q000821:virology*