Antigenic and genetic variations in European and North American equine influenza virus strains (H3N8) isolated from 2006 to 2007

Neil A. Bryant, Adam S. Rash, Colin A. Russell, Julie Ross, Annie Cooke, Samantha Bowman, Shona MacRae, Nicola S. Lewis, Romain Paillot, Reto Zanoni, Hanspeter Meier, Lowri A. Griffiths, Janet M. Daly, Ashish Tiwari, Thomas M. Chambers, J. Richard Newton, Debra M. Elton

Research output: Contribution to journalArticlepeer-review

141 Scopus citations


Equine influenza virus (EIV) surveillance is important in the management of equine influenza. It provides data on circulating and newly emerging strains for vaccine strain selection. To this end, antigenic characterisation by haemaggluttination inhibition (HI) assay and phylogenetic analysis was carried out on 28 EIV strains isolated in North America and Europe during 2006 and 2007. In the UK, 20 viruses were isolated from 28 nasopharyngeal swabs that tested positive by enzyme-linked immunosorbent assay. All except two of the UK viruses were characterised as members of the Florida sublineage with similarity to A/eq/Newmarket/5/03 (clade 2). One isolate, A/eq/Cheshire/1/06, was characterised as an American lineage strain similar to viruses isolated up to 10 years earlier. A second isolate, A/eq/Lincolnshire/1/07 was characterised as a member of the Florida sublineage (clade 1) with similarity to A/eq/Wisconsin/03. Furthermore, A/eq/Lincolnshire/1/06 was a member of the Florida sublineage (clade 2) by haemagglutinin (HA) gene sequence, but appeared to be a member of the Eurasian lineage by the non-structural gene (NS) sequence suggesting that reassortment had occurred. A/eq/Switzerland/P112/07 was characterised as a member of the Eurasian lineage, the first time since 2005 that isolation of a virus from this lineage has been reported. Seven viruses from North America were classified as members of the Florida sublineage (clade 1), similar to A/eq/Wisconsin/03. In conclusion, a variety of antigenically distinct EIVs continue to circulate worldwide. Florida sublineage clade 1 viruses appear to predominate in North America, clade 2 viruses in Europe.

Original languageEnglish
Pages (from-to)41-52
Number of pages12
JournalVeterinary Microbiology
Issue number1-2
StatePublished - Jul 2 2009

Bibliographical note

Funding Information:
We would like to thank Toni-Ann Hammond for excellent technical support for EIV diagnostics, Schering Plough Animal Health and Intervet for subsidising the EIV surveillance programme and Prof. Alan Guthrie (University of Pretoria, SA) for providing us with A/eq/South-Africa/4/03. Study was supported by the Horserace Betting Levy Board (HBLB) and the Animal Health Trust. C.A.R. was supported by a research fellowship from Clare College, University of Cambridge and by the NIH Director's Pioneer Award program, part of the NIH roadmap to medical research, through grant number DP1-OD000490-01. N.S.L. was supported by the Cambridge Infectious Diseases Consortium as part of the DEFRA Veterinary Training and Research Initiative.


  • Equine influenza virus
  • H3N8
  • Surveillance
  • Vaccine strain selection

ASJC Scopus subject areas

  • Microbiology
  • General Veterinary


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