title: Assessment of the safety and efficacy of low pathogenic avian influenza (H9N2) virus in inactivated oil emulsion vaccine in laying hens.
abstract: In Korea, several outbreaks of low pathogenic AI (H9N2) viral infections leading to decreased egg production and increased mortality have been reported on commercial farms since 1996, resulting in severe economic losses. To control the H9N2 LPAI endemic, the Korea Veterinary Authority has permitted the use of the inactivated H9N2 LPAI vaccine since 2007. In this study, we developed a killed vaccine using a low pathogenic H9N2 AI virus (A/chicken/Korea/ADL0401) and conducted safety and efficacy tests in commercial layer farms while focusing on analysis of factors that cause losses to farms, including egg production rate, egg abnormality, and feed efficiency. The egg production rate of the control group declined dramatically 5 days after the challenge. There were no changes in feed consumption of all three groups before the challenge, but rates of the control declined afterward. Clinical signs in the vaccinated groups were similar, and a slight decline in feed consumption was observed after challenge; however, this returned to normal more rapidly than the control group and commercial layers. Overall, the results of this study indicate that the safety and efficacy of the vaccine are adequate to provide protection against the AI field infection (H9N2) epidemic in Korea.
authors.affiliation: Environmental Health Research Division, National Institute of Environmental Research, Incheon 22689, Korea.; Avian Diseases Laboratory, College of Veterinary Medicine, Chungbuk National University, Cheongju 28665, Korea.
authors.forename: Jeong-Hwa
authors.initials: JH
authors.lastname: Shin
authors.affiliation: Avian Diseases Laboratory, College of Veterinary Medicine, Kangwon National University, Chuncheon 24341, Korea.
authors.forename: Jong Seo
authors.initials: JS
authors.lastname: Mo
authors.affiliation: Avian Diseases Laboratory, College of Veterinary Medicine, Chungbuk National University, Cheongju 28665, Korea.
authors.forename: Jong-Nyeo
authors.initials: JN
authors.lastname: Kim
authors.affiliation: Avian Diseases Laboratory, College of Veterinary Medicine, Chungbuk National University, Cheongju 28665, Korea.
authors.forename: In-pil
authors.initials: IP
authors.lastname: Mo
authors.affiliation: Ha Veterinary Clinics, Yeongju 36082, Korea.
authors.forename: Bong-Do
authors.initials: BD
authors.lastname: Ha
mesh_terms: D000818:Animals; D002645:Chickens; D004655:Emulsions; D005260:Female; D053127:Influenza A Virus, H9N2 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000276:immunology* / Q000592:standards*; D005585:Influenza in Birds / Q000276:immunology / Q000517:prevention & control; D052287:Oviparity; D013047:Specific Pathogen-Free Organisms; D015164:Vaccines, Inactivated / Q000276:immunology
chemical_list: D004655:Emulsions; D007252:Influenza Vaccines; D015164:Vaccines, Inactivated
keywords: H9N2; avian influenza virus; immunity; vaccine