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

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

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 assay (HI) and phylogenetic analysis was carried out on 28 equine influenza virus strains isolated in North America and Europe during 2006 and 2007. In the UK, 20 viruses were isolated from 27 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 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 lineage (clade 1) with similarity to A/eq/Wisconsin/03. Futhermore, A/eq/Lincolnshire/1/06 was a member of the Florida sublineage (clade 2) by haemagglutinin gene (HA) 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 equine influenza viruses continue to circulate worldwide. Florida sublineage clade 1 viruses appear to predominate in North America, clade 2 viruses in Europe.

Mots clés: Equine Influenza virus; H3N8; Surveillance; Vaccine strain selection

Neil A. Bryant, Adam S. Rash, Colin A. Russell, Julie Ross, Annie Cooke, et al.. Antigenic and genetic variations in European and North American equine influenza virus strains isolated from 2006 to 2007. Veterinary Microbiology, 2009, 138 (1-2), pp.41. ⟨10.1016/j.vetmic.2009.03.004⟩. ⟨hal-00490548⟩