title: Swine influenza virus infection in different age groups of pigs in farrow-to-finish farms in Thailand.
abstract: BACKGROUND
  Understanding swine influenza virus (SIV) ecology has become more and more important from both the pig industry and public health points of views. However, the mechanism whereby SIV occurs in pig farms is not well understood. The purpose of this study was to develop a proper strategy for SIV surveillance.
  
  
  RESULTS
  We conducted longitudinal monitoring in 6 farrow-to-finish farms in the central region of Thailand from 2008 to 2009. Nasal swabs and serum samples were collected periodically from clinically healthy pigs consisting of sows, fattening pigs, weaned piglets and pigs transferred from other farms. A total of 731 nasal swabs were subjected to virus isolation and 641 serum samples were subjected to detection of SIV antibodies against H1 and H3 subtypes using the hemagglutination inhibition test and ELISA. Twelve SIVs were isolated in this study and eleven were from piglets aged 4 and 8 weeks. Phylogenetical analysis revealed that SIVs isolated from different farms shared a common ancestor. Antibodies against SIVs were detected in fattening pigs on farms with no SIV isolation in the respective periods studied. These observations suggested that piglets aged 8 weeks or younger could be a main target for SIV isolation. Farm-to-farm transmission was suggested for farms where pigs from other farms are introduced periodically. In addition, antibodies against SIVs detected in fattening pigs could be a marker for SIV infection in a farm.
  
  
  CONCLUSIONS
  The present study provided important information on SIV surveillance that will enable better understanding of SIV ecology in farrow-to-finish farms.
authors.affiliation: Thailand-Japan Zoonotic Diseases Collaboration Center, Kasetklang, Chatuchak, Bangkok 10900, Thailand.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Takemae
authors.forename: Sujira
authors.initials: S
authors.lastname: Parchariyanon
authors.forename: Ruttapong
authors.initials: R
authors.lastname: Ruttanapumma
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Hiromoto
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Hayashi
authors.forename: Yuko
authors.initials: Y
authors.lastname: Uchida
authors.forename: Takehiko
authors.initials: T
authors.lastname: Saito
mesh_terms: D000375:Aging / Q000276:immunology*; D000822:Animal Husbandry; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D005260:Female; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D008297:Male; D008969:Molecular Sequence Data; D009976:Orthomyxoviridae Infections / Q000453:epidemiology / Q000635:transmission / Q000662:veterinary* / Q000821:virology; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D011159:Population Surveillance / Q000379:methods; D017422:Sequence Analysis, DNA; D013552:Swine / Q000821:virology*; D013553:Swine Diseases / Q000453:epidemiology* / Q000635:transmission / Q000821:virology; D013785:Thailand / Q000453:epidemiology
chemical_list: D000914:Antibodies, Viral