Abstract
BackgroundOutbreaks of Marek’s disease (MD), caused by Marek’s disease virus (MDV), primarily occur in 10–12-week-old hens.Case presentation 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.ConclusionOur 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.
Highlights
IntroductionOutbreaks of Marek’s disease (MD), caused by Marek’s disease virus (MDV), primarily occur in 10–12-week-old hens
Outbreaks of Marek’s disease (MD), caused by Marek’s disease virus (MDV), primarily occur in 10–12-week-old hens.Case presentation: We report a case of MD in a breeding flock of 24–30-week-old vaccinated broilers in China
Our data provide evidence that 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
Summary
Outbreaks of Marek’s disease (MD), caused by Marek’s disease virus (MDV), primarily occur in 10–12-week-old hens. Case presentation: We report a case of MD in a breeding flock of 24–30-week-old vaccinated broilers in China. Vaccination plays a vital role in the prevention and control of MD globally, MDVs of increased virulence have been frequently isolated in some countries, even among vaccinated chickens, calling into question the current vaccination program against MDVs. The virulent MDVs (vMDVs) usually carry mutations in genes such as pp, meq, or gB, that are associated with the oncogenicity and and their immune evasion [2, 3]. We report a recent outbreak of MD in a vaccinated breeding broiler flock in China during its peak egg-laying period
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