title: Outbreak of Marek's disease in a vaccinated broiler breeding flock during its peak egg-laying period in China.
abstract: BACKGROUND
  Outbreaks of Marek's disease (MD), caused by Marek's disease virus (MDV), primarily occur in 10-12-week-old hens.
  
  
  METHODS
  We report a case of MD in a breeding flock of 24-30-week-old vaccinated broilers in China. The clinical signs in the affected chickens appeared at 24 weeks, and the incidence of tumours peaked at 30 weeks. The morbidity and mortality of the hens were 5 % and 80 %, respectively. Hematoxylin-eosin staining of the tissues showed the typical characteristics of MD. MDV infection was confirmed in the hens with an agar gel diffusion precipitation assay for the MD antigen in the feather follicle epithelium. An MDV strain, designated AH1410, was isolated from the blood lymphocytes. Sequence analyses of the pp38, meq, and gB genes revealed that strain AH1410 had molecular features consistent with a virulent, previously identified MDV.
  
  
  CONCLUSIONS
  Our data provide evidence that not only is MDV becoming more virulent, but that the period of its onset in chickens is expanding. These findings provide the basis the molecular surveillance and further study of virulent MDV mutants and control strategies for MD in China.
authors.affiliation: Ministry of Education Key Laboratory for Avian Preventive Medicine, Yangzhou University, No. 12 East Wenhui Road, Yangzhou, Jiangsu, 225009, P.R. China. ayu1838@qq.com.
authors.forename: Xinyu
authors.initials: X
authors.lastname: Zhuang
authors.affiliation: Ministry of Education Key Laboratory for Avian Preventive Medicine, Yangzhou University, No. 12 East Wenhui Road, Yangzhou, Jiangsu, 225009, P.R. China. feilinshiji@126.com.
authors.forename: Haitao
authors.initials: H
authors.lastname: Zou
authors.affiliation: Ministry of Education Key Laboratory for Avian Preventive Medicine, Yangzhou University, No. 12 East Wenhui Road, Yangzhou, Jiangsu, 225009, P.R. China. hyshi@yzu.edu.cn.|Key Laboratory of Jiangsu Preventive Veterinary Medicine, Yangzhou University, Yangzhou, 225009, P.R. China. hyshi@yzu.edu.cn.|Jiangsu Co-innovation Center for the Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, P.R. China. hyshi@yzu.edu.cn.
authors.forename: Huoying
authors.initials: H
authors.lastname: Shi
authors.affiliation: Ministry of Education Key Laboratory for Avian Preventive Medicine, Yangzhou University, No. 12 East Wenhui Road, Yangzhou, Jiangsu, 225009, P.R. China. hxshao@yzu.edu.cn.|Key Laboratory of Jiangsu Preventive Veterinary Medicine, Yangzhou University, Yangzhou, 225009, P.R. China. hxshao@yzu.edu.cn.|Jiangsu Co-innovation Center for the Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, P.R. China. hxshao@yzu.edu.cn.
authors.forename: Hongxia
authors.initials: H
authors.lastname: Shao
authors.affiliation: Ministry of Education Key Laboratory for Avian Preventive Medicine, Yangzhou University, No. 12 East Wenhui Road, Yangzhou, Jiangsu, 225009, P.R. China. jqye@yzu.edu.cn.|Key Laboratory of Jiangsu Preventive Veterinary Medicine, Yangzhou University, Yangzhou, 225009, P.R. China. jqye@yzu.edu.cn.|Jiangsu Co-innovation Center for the Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, P.R. China. jqye@yzu.edu.cn.
authors.forename: Jianqiang
authors.initials: J
authors.lastname: Ye
authors.affiliation: Key Laboratory of Jiangsu Preventive Veterinary Medicine, Yangzhou University, Yangzhou, 225009, P.R. China. miaoji.chn@gmail.com.
authors.forename: Ji
authors.initials: J
authors.lastname: Miao
authors.affiliation: Key Laboratory of Jiangsu Preventive Veterinary Medicine, Yangzhou University, Yangzhou, 225009, P.R. China. wugenghua@aliyun.com.
authors.forename: Genghua
authors.initials: G
authors.lastname: Wu
authors.affiliation: Ministry of Education Key Laboratory for Avian Preventive Medicine, Yangzhou University, No. 12 East Wenhui Road, Yangzhou, Jiangsu, 225009, P.R. China. aijian@yzu.edu.cn.|Key Laboratory of Jiangsu Preventive Veterinary Medicine, Yangzhou University, Yangzhou, 225009, P.R. China. aijian@yzu.edu.cn.|Jiangsu Co-innovation Center for the Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, P.R. China. aijian@yzu.edu.cn.
authors.forename: Aijian
authors.initials: A
authors.lastname: Qin
mesh_terms: D000818:Animals; D002645:Chickens; D002681:China; D004196:Disease Outbreaks / Q000662:veterinary*; D005260:Female; D025922:Mardivirus / Q000302:isolation & purification / Q000472:pathogenicity; D008380:Marek Disease / Q000453:epidemiology / Q000517:prevention & control*; D010058:Oviposition; D014765:Viral Vaccines / Q000008:administration & dosage / Q000276:immunology*; D014774:Virulence
chemical_list: D014765:Viral Vaccines