title: Risk factors for exposure to influenza a viruses, including subtype H5 viruses, in Thai free-grazing ducks.
abstract: Free-grazing ducks (FGD) have been associated with highly pathogenic avian influenza (HPAI) H5N1 outbreaks and may be a viral reservoir. In July-August 2010, we assessed influenza exposure of Thai FGD and risk factors thereof. Serum from 6254 ducks was analysed with enzyme-linked immunosorbent assay (ELISA) to detect antibodies to influenza A nucleoprotein (NP), and haemagglutinin H5 protein. Eighty-five per cent (5305 ducks) were seropositive for influenza A. Of the NP-seropositive sera tested with H5 assays (n = 1423), 553 (39%) were H5 ELISA positive and 57 (4%) suspect. Twelve per cent (74 of 610) of H5 ELISA-positive/suspect ducks had H5 titres ≥ 1 : 20 by haemagglutination inhibition. Risk factors for influenza A seropositivity include older age, poultry contact, flock visitors and older purchase age. Study flocks had H5 virus exposure as recently as March 2010, but no HPAI H5N1 outbreaks have been identified in Thailand since 2008, highlighting a need for rigorous FGD surveillance.
authors.affiliation: University of Minnesota Twin Cities, Saint Paul, MN, USA.
authors.forename: A L
authors.initials: AL
authors.lastname: Beaudoin
authors.forename: P
authors.initials: P
authors.lastname: Kitikoon
authors.forename: P J
authors.initials: PJ
authors.lastname: Schreiner
authors.forename: R S
authors.initials: RS
authors.lastname: Singer
authors.forename: J
authors.initials: J
authors.lastname: Sasipreeyajan
authors.forename: A
authors.initials: A
authors.lastname: Amonsin
authors.forename: M R
authors.initials: MR
authors.lastname: Gramer
authors.forename: S
authors.initials: S
authors.lastname: Pakinsee
authors.forename: J B
authors.initials: JB
authors.lastname: Bender
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004196:Disease Outbreaks / Q000662:veterinary; D004372:Ducks; D004797:Enzyme-Linked Immunosorbent Assay; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D053124:Influenza A Virus, H5N1 Subtype; D009980:Influenza A virus / Q000145:classification* / Q000276:immunology; D005585:Influenza in Birds / Q000097:blood / Q000453:epidemiology* / Q000821:virology; D012307:Risk Factors; D016036:Seroepidemiologic Studies; D013785:Thailand / Q000453:epidemiology
chemical_list: D000914:Antibodies, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus; C109963:hemagglutinin, avian influenza A virus
keywords: Thailand; avian influenza; ducks; risk factors; serology