title: Pathogenic characteristics of Marek's disease virus field strains prevalent in China and the effectiveness of existing vaccines against them.
abstract: The virulence of Marek's disease virus (MDV) is continuously evolving, and more virulent MDV pathotypes are emerging, thereby reducing the effectiveness of the existing vaccines. In this study, feather pulps were collected from diseased chickens in commercial chicken flocks in China that presented significant MD visceral tumors in 2011 and were inoculated into a monolayer of duck embryo fibroblasts (DEFs). Three field isolates of MDV were obtained by plaque cloning and identified as MDV via PCR and designated strains LCC, LLY, and LTS. Unvaccinated and CVI988 vaccine-vaccinated specific pathogen-free chickens were challenged at 7 days post vaccination (dpv) with 1000 plaque forming units of each of the respective MDV isolates. These strains induced gross MD lesions in all (100%) of the unvaccinated chickens, and the mortality rates of the unvaccinated chickens were 42.9%, 46.7%, and 23.1% by 60 days post challenge (dpc), respectively. The CVI988 vaccine induced protective indices (PIs) of 85.7, 92.3, and 66.7, respectively. These results showed that the pathogenic characteristics of the Chinese isolates were diverse and that vaccine CVI988 provided different levels of protection against them. These data indicated that the existence of variant MDV strains was a possible reason of immunity failure in China.
authors.affiliation: Northeast Agricultural University, Harbin 150030, PR China; Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Yan-ping
authors.initials: YP
authors.lastname: Zhang
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Zhi-jie
authors.initials: ZJ
authors.lastname: Li
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Ke-yan
authors.initials: KY
authors.lastname: Bao
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Hong-chao
authors.initials: HC
authors.lastname: Lv
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Yu-long
authors.initials: YL
authors.lastname: Gao
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Hong-lei
authors.initials: HL
authors.lastname: Gao
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Xiao-le
authors.initials: XL
authors.lastname: Qi
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Hong-yu
authors.initials: HY
authors.lastname: Cui
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Yong-qiang
authors.initials: YQ
authors.lastname: Wang
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Xian-gang
authors.initials: XG
authors.lastname: Ren
authors.affiliation: Northeast Agricultural University, Harbin 150030, PR China; Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China. Electronic address: xmw@hvri.ac.cn.
authors.forename: Xiao-mei
authors.initials: XM
authors.lastname: Wang
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China. Electronic address: liucj93711@hvri.ac.cn.
authors.forename: Chang-jun
authors.initials: CJ
authors.lastname: Liu
mesh_terms: D000818:Animals; D002645:Chickens / Q000276:immunology; D002681:China / Q000453:epidemiology; D005241:Feathers / Q000821:virology; D008381:Herpesvirus 2, Gallid / Q000235:genetics*; D008380:Marek Disease / Q000453:epidemiology / Q000517:prevention & control / Q000821:virology*; D022501:Marek Disease Vaccines / Q000276:immunology*; D016133:Polymerase Chain Reaction; D015995:Prevalence; D013047:Specific Pathogen-Free Organisms; D014774:Virulence / Q000187:drug effects
chemical_list: D022501:Marek Disease Vaccines
keywords: China; Marek's disease virus; Pathogenicity; Prevalent