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News Article

Marek’s disease virus: genes associated with virulence identified

A study of U.S. strains has revealed a number of MDV genes associated with virulence, as would be expected for a complex trait

Veterinary medical officer John Dunn and his team at the Agricultural Research Service (ARS) Avian Disease and Oncology Laboratory in Michigan, USA, analysed the genomes of different strains of Marek's disease virus (MDV, Gallid herpesvirus 2) to find genes associated with virulence. They sequenced DNA from 70 virus strains, collected over the years from across the United States, and identified significant genetic variants associated with virulence.

The study, published in the Journal of General Virology, also revealed that high virulence strains collected from the same farms recently and in the 1990s were nearly identical. This illustrates the ease with which virulent MDV can persist and spread between flocks as well as the difficulty in eradicating the disease from a farm once established, Dunn said.

It was found that new strains were no more virulent than older strains, which may suggest that current management and vaccine practices have slowed the ongoing evolution of the virus, according to Dunn.

What separates this research from other studies is the uniformity of how virus strains were phenotyped, Dunn said. Only U.S. strains were analysed, which were all collected, isolated and phenotyped in the same inbred chicken lines and controlled conditions, using the same vaccines and control viruses. In addition, all strains were phenotyped by one of two ARS veterinarians.

The next step is to validate markers associated with virulence to determine if these markers may provide an alternative to live bird testing for evaluating virulence of new MDV field strains.

Article: Dunn, J. R.; Black Pyrkosz, A.; Steep, A.; Cheng, H. H. (2019). Identification of Marek’s disease virus genes associated with virulence of US strains. Journal of General Virology, 100(7), doi: 10.1099/jgv.0.001288

Article details

  • Date
  • 23 August 2019
  • Source
  • USDA