MDV is an economically important oncogenic herpesvirus of poultry, according to Katherine E. Atkins of Yale School of Medicine in the US and co-authors at the University of Edinburgh in Scotland, Pennsylvania State University in the US and Australia’s University of New England.

In a paper published in BMC Veterinary Research, they explain that since the 1960s, increasingly virulent strains of Marek’s disease have caused continued poultry industry production losses worldwide.

To understand the mechanisms of this virulence evolution and to evaluate the epidemiological consequences of putative control strategies, it is imperative to understand how virulence is defined and how this correlates with host mortality and infectiousness during MDV infection.

The international group presents a mathematical approach to quantify key epidemiological parameters. Host lifespan, virus latent periods and host viral shedding rates were estimated for unvaccinated and vaccinated birds, infected with one of three MDV strains. The strains had previously been pathotyped to assign virulence scores according to pathogenicity of strains in hosts.

The researchers’ analyses show that strains of higher virulence have a higher viral shedding rate, and more rapidly kill hosts. Vaccination enhances host life expectancy but does not significantly reduce the shedding rate of the virus, they found.

While the primary latent period of the virus does not vary with challenge strain or vaccine treatment of host, time until the maximum viral shedding rate is increased with vaccination.

Atkins and co-authors conclude that their approach provides the tools necessary for a formal analysis of the evolution of virulence in MDV, and potentially simpler and cheaper approaches for comparing the virulence of MDV strains.

Reference

Atkins K.E., A.F. Read, N.J. Savill, K.G. Renz, S.W. Walkden-Brown and M.E.J. Woolhouse. 2011. Modelling Marek’s disease virus infection: Parameter estimates for mortality rate and infectiousness. BMC Veterinary Research, 7:70. doi:10.1186/1746-6148-7-70

Further Reading

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Further Reading

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Find out more information on Marek’s disease by clicking here.