title: Suboptimal protection against H5N1 highly pathogenic avian influenza viruses from Vietnam in ducks vaccinated with commercial poultry vaccines.
abstract: Domestic ducks are the second most abundant poultry species in many Asian countries including Vietnam, and play a critical role in the epizootiology of H5N1 highly pathogenic avian influenza (HPAI) [FAO]. In this study, we examined the protective efficacy in ducks of two commercial H5N1 vaccines widely used in Vietnam; Re-1 containing A/goose/Guangdong/1/1996 hemagglutinin (HA) clade 0 antigens, and Re-5 containing A/duck/Anhui/1/2006 HA clade 2.3.4 antigens. Ducks received two doses of either vaccine at 7 and at 14 or 21 days of age followed by challenge at 30 days of age with viruses belonging to the HA clades 1.1, 2.3.4.3, 2.3.2.1.A and 2.3.2.1.B isolated between 2008 and 2011 in Vietnam. Ducks vaccinated with the Re-1 vaccine were protected after infection with the two H5N1 HPAI viruses isolated in 2008 (HA clades 1.1 and 2.3.4.3) showing no mortality and limited virus shedding. The Re-1 and Re-5 vaccines conferred 90-100% protection against mortality after challenge with the 2010 H5N1 HPAI viruses (HA clade 2.3.2.1.A); but vaccinated ducks shed virus for more than 7 days after challenge. Similarly, the Re-1 and Re-5 vaccines only showed partial protection against the 2011 H5N1 HPAI viruses (HA clade 2.3.2.1.A and 2.3.2.1.B), with a high proportion of vaccinated ducks shedding virus for more than 10 days. Furthermore, 50% mortality was observed in ducks vaccinated with Re-1 and challenged with the 2.3.2.1.B virus. The HA proteins of the 2011 challenge viruses had the greatest number of amino acid differences from the two vaccines as compared to the viruses from 2008 and 2009, which correlates with the lesser protection observed with these viruses. These studies demonstrate the suboptimal protection conferred by the Re-1 and Re-5 commercial vaccines in ducks against H5N1 HPAI clade 2.3.2.1 viruses, and underscore the importance of monitoring vaccine efficacy in the control of H5N1 HPAI in ducks.
authors.affiliation: Exotic and Emerging Avian Viral Diseases Unit, Southeast Poultry Research Laboratory, USDA-Agricultural Research Service, 934 College Station Road, Athens, GA 30605, USA.
authors.forename: Ra Mi
authors.initials: RM
authors.lastname: Cha
authors.forename: Diane
authors.initials: D
authors.lastname: Smith
authors.forename: Eric
authors.initials: E
authors.lastname: Shepherd
authors.forename: C Todd
authors.initials: CT
authors.lastname: Davis
authors.forename: Ruben
authors.initials: R
authors.lastname: Donis
authors.forename: Tung
authors.initials: T
authors.lastname: Nguyen
authors.forename: Hoang Dang
authors.initials: HD
authors.lastname: Nguyen
authors.forename: Hoa Thi
authors.initials: HT
authors.lastname: Do
authors.forename: Ken
authors.initials: K
authors.lastname: Inui
authors.forename: David L
authors.initials: DL
authors.lastname: Suarez
authors.forename: David E
authors.initials: DE
authors.lastname: Swayne
authors.forename: Mary
authors.initials: M
authors.lastname: Pantin-Jackwood
mesh_terms: D000818:Animals; D004372:Ducks; D053124:Influenza A Virus, H5N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D005585:Influenza in Birds / Q000276:immunology / Q000517:prevention & control* / Q000821:virology*; D016019:Survival Analysis; D014611:Vaccination / Q000379:methods*; D014744:Vietnam
chemical_list: D007252:Influenza Vaccines
keywords: Ducks; H5N1 highly pathogenic avian influenza; Protection; Vaccine