title: Genetic evolution of equine influenza strains isolated in France  from 2005 to 2010.
abstract: REASON FOR PERFORMING THIS STUDY: Equine influenza virus (EIV) is considered the most economically important equine respiratory pathogen worldwide. The H3N8 subtype, responsible for all outbreaks of equine influenza globally, evolves perpetually. Mutations in the genome of these viruses have the potential to modify their antigenic properties and recognition by pre-existing antibodies.
  
  
  OBJECTIVE
  The aim of this study was to determine the genetic evolution of EIV strains in France and to compare it with the evolution of strains isolated globally. Analysis of the sequence data was performed to investigate any possible links between the outbreaks.
  
  
  METHODS
  Retrospective genetic analysis study of archived material.
  
  
  METHODS
  Analyses were performed on the HA1 domain of haemagglutinin H3 of EIV isolated in a previous study carried out from November 2005 to October 2010. The nucleic acid sequence of 41 strains was analysed and translated. The French viruses were compared with 59 Clade 1 strains and 83 Clade 2 strains. Strains were aligned chronologically and on the basis of their geographical origin.
  
  
  RESULTS
  The 16 Clade 1 strains are all derived from the outbreak that started in the Grosbois training yard in 2009. The virus genome appears to have been stable during the outbreak. The 25 Clade 2 strains were isolated over the 5-year period during which several mutations had emerged. Some strains incorporate a sporadic mutation, and others a mutation that may occur several times but does not persist. However, all strains are gradually moving towards definitive mutations.
  
  
  CONCLUSIONS
  This study demonstrated that EIVs have evolved in France during this period in a similar manner to EIVs globally. The data lend support to the current World Animal Health Organisation recommendation that the vaccines contain a representative of both Clade 1 and Clade 2 of the Florida sublineage.
authors.forename: L J
authors.initials: LJ
authors.lastname: Legrand
authors.forename: P-H Y
authors.initials: PH
authors.lastname: Pitel
authors.forename: A A
authors.initials: AA
authors.lastname: Cullinane
authors.forename: G D
authors.initials: GD
authors.lastname: Fortier
authors.forename: S L
authors.initials: SL
authors.lastname: Pronost
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D004196:Disease Outbreaks / Q000662:veterinary; D005602:France / Q000453:epidemiology; D015967:Gene Expression Regulation, Viral / Q000502:physiology; D006734:Horse Diseases / Q000453:epidemiology / Q000821:virology*; D006736:Horses; D053123:Influenza A Virus, H3N8 Subtype / Q000235:genetics* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D009976:Orthomyxoviridae Infections / Q000453:epidemiology / Q000662:veterinary* / Q000821:virology; D012189:Retrospective Studies; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D014764:Viral Proteins