title: Modelling Marek's disease virus (MDV) infection: parameter estimates for mortality rate and infectiousness.
abstract: BACKGROUND
  Marek's disease virus (MDV) is an economically important oncogenic herpesvirus of poultry. Since the 1960s, increasingly virulent strains 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. We present 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.
  
  
  RESULTS
  Our 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. While the primary latent period of the virus does not vary with challenge strain nor vaccine treatment of host, the time until the maximum viral shedding rate is increased with vaccination.
  
  
  CONCLUSIONS
  Our approach provides the tools necessary for a formal analysis of the evolution of virulence in MDV, and potentially simpler and cheaper approaches to comparing the virulence of MDV strains.
authors.affiliation: Centre for Infectious Diseases, University Of Edinburgh, West Mains Road, Edinburgh, UK. . katherine.atkins@yale.edu
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Atkins
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Read
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Savill
authors.forename: Katrin G
authors.initials: KG
authors.lastname: Renz
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Walkden-Brown
authors.forename: Mark E J
authors.initials: ME
authors.lastname: Woolhouse
mesh_terms: D000818:Animals; D002645:Chickens / Q000821:virology; D025922:Mardivirus / Q000472:pathogenicity* / Q000502:physiology; D008380:Marek Disease / Q000401:mortality / Q000821:virology*; D008954:Models, Biological; D011201:Poultry Diseases / Q000401:mortality / Q000821:virology*; D014422:Turkeys / Q000821:virology; D014774:Virulence; D017735:Virus Latency; D017201:Virus Shedding
references.citation: J Virol Methods. 1999 Sep;82(1):27-37
references.pmid: 10507410
references.citation: Avian Pathol. 2005 Apr;34(2):75-90
references.pmid: 16191686
references.citation: Nat Rev Microbiol. 2006 Apr;4(4):283-94
references.pmid: 16541136
references.citation: Nature. 1969 Feb 22;221(5182):744-7
references.pmid: 4304053
references.citation: Avian Dis. 2000 Oct-Dec;44(4):770-5
references.pmid: 11195630
references.citation: J Gen Virol. 2005 Nov;86(Pt 11):2989-2998
references.pmid: 16227220
references.citation: Avian Pathol. 2008 Jun;37(3):225-35
references.pmid: 18568648
references.citation: Trends Microbiol. 1994 Mar;2(3):73-6
references.pmid: 8156274
references.citation: J Virol. 2005 Apr;79(7):4545-9
references.pmid: 15767457
references.citation: Crit Rev Microbiol. 1986;12(4):293-320
references.pmid: 3007026
references.citation: Vet Immunol Immunopathol. 2006 Jul 15;112(1-2):78-86
references.pmid: 16682084
references.citation: J Virol Methods. 2004 Aug;119(2):103-13
references.pmid: 15158591
references.citation: Virology. 2004 Oct 10;328(1):142-50
references.pmid: 15380365
references.citation: J Virol Methods. 2006 Mar;132(1-2):127-34
references.pmid: 16290211
references.citation: Avian Dis. 1973 Oct-Dec;17(4):767-81
references.pmid: 4203252
references.citation: Science. 1982 Feb 26;215(4536):1053-60
references.pmid: 7063839
references.citation: Avian Pathol. 2001 Oct;30(5):525-33
references.pmid: 19184942
references.citation: Aust Vet J. 2007 Sep;85(9):348-55
references.pmid: 17760936
references.citation: Avian Dis. 1971 Apr-Jun;15(2):346-65
references.pmid: 4325825
references.citation: J Virol Methods. 1997 Apr;65(1):75-81
references.pmid: 9128864
references.citation: J Virol Methods. 2005 Jan;123(1):53-64
references.pmid: 15582699
references.citation: Avian Dis. 2002 Oct-Dec;46(4):909-18
references.pmid: 12495052
references.citation: Avian Dis. 1970 May;14(2):219-33
references.pmid: 4316765
references.citation: Avian Dis. 1997 Jan-Mar;41(1):149-63
references.pmid: 9087332