title: Molecular epidemiology of avian influenza viruses circulating among healthy poultry flocks in farms in northern Vietnam.
abstract: Repeated epizootics of highly pathogenic avian influenza (HPAI) virus subtype H5N1 were reported from 2003 to 2005 among poultry in Vietnam. More than 200 million birds were killed to control the spread of the disease. Human cases of H5N1 infection have been sporadically reported in an area where repeated H5N1 outbreaks among birds had occurred. Subtype H5N1 strains are established as endemic among poultry in Vietnam, however, insights into how avian influenza viruses including the H5N1 subtype are maintained in endemic areas is not clear. In order to determine the prevalence of different avian influenza viruses (AIVs), including H5N1 circulating among poultry in northern Vietnam, surveillance was conducted during the years 2006-2009. A subtype H5N1 strain was isolated from an apparently healthy duck reared on a farm in northern Vietnam in 2008 and was identified as an HPAI. Although only one H5N1 virus was isolated, it supports the view that healthy domestic ducks play a pivotal role in maintaining and transmitting H5N1 viruses which cause disease outbreaks in northern Vietnam. In addition, a total of 26 AIVs with low pathogenicity were isolated from poultry and phylogenetic analysis of all the eight gene segments revealed their diverse genetical backgrounds, implying that reassortments have occurred frequently among strains in northern Vietnam. It is, therefore, important to monitor the prevalence of influenza viruses among healthy poultry between epidemics in an area where AIVs are endemic.
authors.affiliation: Kyoto Sangyo University, Kamigamo-motoyama, Kita, Kyoto, Japan. tyamashi@nagasaki-u.ac.jp
authors.forename: Hiroki
authors.initials: H
authors.lastname: Takakuwa
authors.forename: Tetsu
authors.initials: T
authors.lastname: Yamashiro
authors.forename: Mai Q
authors.initials: MQ
authors.lastname: Le
authors.forename: Lien S
authors.initials: LS
authors.lastname: Phuong
authors.forename: Hiroichi
authors.initials: H
authors.lastname: Ozaki
authors.forename: Ryota
authors.initials: R
authors.lastname: Tsunekuni
authors.forename: Tatsufumi
authors.initials: T
authors.lastname: Usui
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ito
authors.forename: Masami
authors.initials: M
authors.lastname: Morimatsu
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Tomioka
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Ito
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Murase
authors.forename: Etsuro
authors.initials: E
authors.lastname: Ono
authors.forename: Koichi
authors.initials: K
authors.lastname: Otsuki
mesh_terms: D000818:Animals; D002645:Chickens; D002988:Cloaca / Q000821:virology; D004372:Ducks; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D053124:Influenza A Virus, H5N1 Subtype / Q000737:chemistry / Q000145:classification* / Q000302:isolation & purification; D005585:Influenza in Birds / Q000453:epidemiology* / Q000821:virology; D051379:Mice; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D009439:Neuraminidase / Q000235:genetics; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000662:veterinary; D011201:Poultry Diseases / Q000453:epidemiology* / Q000821:virology; D017422:Sequence Analysis, DNA / Q000662:veterinary; D020539:Sequence Analysis, Protein; D014132:Trachea / Q000821:virology; D014744:Vietnam / Q000453:epidemiology
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D009439:Neuraminidase