title: Re-evaluation the immune efficacy of Newcastle disease virus vaccine in commercial laying chickens.
abstract: Newcastle disease virus (NDV) infection causes serious problems in laying chickens, like reducing egg production, increasing rate of abnormal eggs in spite of strict vaccination in layer farms program. A new evaluation system is needed to show complete protection of the immunization in laying chickens based on the egg-laying performance, rather than clinical signs of the disease. In this study, laying chickens with different anti-NDV HI (hemagglutination-inhibition) antibody titer after vaccination were divided into different groups. These chickens were then challenged with field isolated highly virulent NDV strains. Results showed that the chickens in low HI titers group (5log2 to 8log2) and medium HI titers group (9log2 to 11log2) had atypical symptoms, produced abnormal eggs, and shed virus. Whereas, with HI titers≥12log2, the chickens were completely protected, and did not show symptoms, or produce abnormal eggs or shed virus. Morbidity, positive viral shedding rate and abnormal egg-rate decreased with increase in pre-challenge HI antibody titer. Our result suggested that 12log2 is the threshold of the HI antibody in providing complete protection to laying chickens under field condition, and protective efficacy is correlated with HI antibody titer. This study provides a valuable reference for the vaccination and control of ND in poultry.
authors.affiliation: College of Veterinary Medicine, Northwest A&F University, Yangling 712100, Shaanxi Province, PR China; Department of Animal Science, Wenzhou Vocational College of Scienc & Technology, Wenzhou 325006, Zhejiang, PR China.
authors.forename: Qingsong
authors.initials: Q
authors.lastname: Han
authors.affiliation: College of Veterinary Medicine, Northwest A&F University, Yangling 712100, Shaanxi Province, PR China.
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Gao
authors.affiliation: College of Veterinary Medicine, Northwest A&F University, Yangling 712100, Shaanxi Province, PR China.
authors.forename: Pengpeng
authors.initials: P
authors.lastname: Wu
authors.affiliation: College of Veterinary Medicine, Northwest A&F University, Yangling 712100, Shaanxi Province, PR China.
authors.forename: Sa
authors.initials: S
authors.lastname: Xiao
authors.affiliation: College of Veterinary Medicine, Northwest A&F University, Yangling 712100, Shaanxi Province, PR China.
authors.forename: Xinglong
authors.initials: X
authors.lastname: Wang
authors.affiliation: College of Veterinary Medicine, Northwest A&F University, Yangling 712100, Shaanxi Province, PR China.
authors.forename: Peng
authors.initials: P
authors.lastname: Liu
authors.affiliation: College of Veterinary Medicine, Northwest A&F University, Yangling 712100, Shaanxi Province, PR China.
authors.forename: Lina
authors.initials: L
authors.lastname: Tong
authors.affiliation: College of Veterinary Medicine, Northwest A&F University, Yangling 712100, Shaanxi Province, PR China.
authors.forename: Huafang
authors.initials: H
authors.lastname: Hao
authors.affiliation: College of Veterinary Medicine, Northwest A&F University, Yangling 712100, Shaanxi Province, PR China.
authors.forename: Shuxia
authors.initials: S
authors.lastname: Zhang
authors.affiliation: College of Veterinary Medicine, Northwest A&F University, Yangling 712100, Shaanxi Province, PR China.
authors.forename: Ruyi
authors.initials: R
authors.lastname: Dang
authors.affiliation: College of Veterinary Medicine, Northwest A&F University, Yangling 712100, Shaanxi Province, PR China. Electronic address: yzq1106@nwsuaf.edu.cn.
authors.forename: Zengqi
authors.initials: Z
authors.lastname: Yang
mesh_terms: D000818:Animals; D002645:Chickens; D005260:Female; D006385:Hemagglutination Inhibition Tests / Q000662:veterinary; D009521:Newcastle Disease / Q000517:prevention & control* / Q000821:virology; D009522:Newcastle disease virus / Q000276:immunology*; D011201:Poultry Diseases / Q000517:prevention & control* / Q000821:virology; D013047:Specific Pathogen-Free Organisms; D014765:Viral Vaccines / Q000008:administration & dosage / Q000276:immunology*; D017201:Virus Shedding
chemical_list: D014765:Viral Vaccines
keywords: Egg quality; HI titer; Immune response; Newcastle disease virus; Viral shedding