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Grippe équine

OIE Expert Surveillance Panel on Equine Influenza Vaccine Composition, OIE Headquarters, 1 March 2016

Conclusions and Recommendations

  • Influenza activity in 2015

During this period, individual animal cases and outbreaks of equine influenza were reported by China, France, Germany, Ireland, Malaysia, Sweden, the UK and the USA.

  • Sources of viruses characterised during 2015

Equine influenza A (H3N8) viruses were isolated and/or characterised from outbreaks in China, France, Ireland, Malaysia, Sweden, the UK and the USA.

  • Field data

There was increased influenza activity in the USA in 2015 with outbreaks detected on 46 premises in 23 states. No vaccination data were available.

In Europe equine influenza virus infections were confirmed in both vaccinated and unvaccinated horses. The majority of the clinically affected horses were unvaccinated or of unknown/lapsed vaccination history.  However vaccination breakdown was recorded in a small number of horses in several countries.

In Asia equine influenza outbreaks were reported in three provinces in China. In Malaysia an outbreak of equine influenza led to the cancellation of racing and activities related to horses for one month, including importation. The index cases were imported horses that were vaccinated against equine influenza on the day of departure from the quarantine facility to various turf clubs, and started showing mild respiratory signs upon arrival at the turf clubs in Selangor and Perak. With the exception of imported horses, racehorses and other local horses in Malaysia are not vaccinated against equine influenza.

  • Characterisation of viruses isolated in 2015

Viruses isolated/identified from outbreaks in China, France, Ireland, Malaysia, Sweden, the UK and the USA were characterised genetically by sequencing of the haemagglutinin (HA) and the neuraminidase (NA) genes.

Viruses isolated in Ireland, the UK and the USA were also characterised antigenically by the haemagglutination inhibition (HI) assay using post-infection ferret antisera and chicken red blood cells.

  • Genetic characterisation

All HA sequences obtained from viruses were of the American lineage (Florida sublineage).  The viruses detected in the USA and Malaysia in 2015, were characterised as clade 1 viruses and were very similar. Viruses detected in China, France, Ireland, Sweden and the UK were characterised as clade 2 viruses.

Three subpopulations of clade 2 viruses have been identified, two circulating in Europe and one in Asia. Compared to the Florida clade 2 reference strain, the viruses identified in 2015 in Ireland and the United Kingdom had the substitution A144V, in contrast to the viruses identified in France and Sweden which had the substitution I179V. These changes were first identified in 2011. The viruses identified in China in 2015 were distinguishable from those circulating in Europe by the substitution A144T; these were similar to those identified in Mongolia in 2011.

The NA gene sequences of viruses from clade 1 and clade 2 were clearly distinguishable as were to a lesser extent, the sequences of viruses from the three subpopulations of clade 2.

Representative sequences for HA and NA are available on GenBank and GISAID

  • Antigenic characteristics

HI data available for viruses isolated in 2015, and antigenic cartography analyses thereof, show that the two clades of the Florida sublineage continue to co-circulate and evolve but currently remain antigenically closely related to the recommended vaccine viruses of that lineage.

  • Conclusions

No viruses belonging to the Eurasian sublineage were detected in 2015.  Viruses isolated and characterised were from clades 1 and 2 of the Florida sublineage. Clade 2 viruses were associated with vaccination breakdown.

  • Level of surveillance and updating of vaccines

The panel continues to emphasize the importance of increased surveillance and investigation of vaccination breakdown in different countries. Increased surveillance in Asia has been facilitated by the OIE Twinning programme.  Rapid submission of viruses to reference laboratories is essential if antigenic and genetic drift is to be monitored effectively on a global basis.

Although some vaccines have been updated to include a virus from clade 2, in accordance with the recommendations of 2010 to 2015, the majority of current vaccines contain outdated strains. The updating of vaccines with epidemiologically relevant viruses is necessary for optimum protection.

  • Recommendations

These are unchanged from those made each year since 2010.

It is not necessary to include an H7N7 virus or an H3N8 virus of the Eurasian lineage in vaccines as these viruses have not been detected in the course of the most recent surveillance and are therefore presumed not to be circulating.

Vaccines should contain both clade 1 and clade 2 viruses of the Florida sublineage. 

Clade 1 continues to be represented by A/eq/South Africa/04/2003-like or A/eq/Ohio/2003-like viruses but more recent clade 1 viruses are available from the OIE reference laboratories.

Clade 2 continues to be represented by A/eq/Richmond/1/2007-like viruses but more recent clade 2 viruses are available from the OIE reference laboratories.

Manufacturers producing vaccines for a strictly national market are encouraged to liaise with reference laboratories.  The selected viruses should induce responses which are immunogenically relevant to the equine influenza viruses circulating nationally. Sequence determination of both HA and NAs should be completed before use.

  • Reference reagents

Freeze-dried post-infection equine antisera to A/eq/Newmarket/1/93 (American lineage H3N8) and A/eq/South Africa/4/2003 (Florida clade 1, sublineage of the American lineage) are available from the European Directorate for the Quality of Medicines (EDQM). These sera have been assigned Single Radial Haemolysis values through an international collaborative study and can be used as primary reference sera for the assay. The panel welcomes the decision by the OIE Biological Standards Commission to agree the proposal for a joint OIE and EDQM collaborative study to produce a new standard antiserum against the reference strain A/eq/Richmond/1/2007, representative of Florida clade 2.

Recent virus strains, including suitable vaccine candidates for clades 1 and 2, are available from the OIE reference laboratories. In the event that an OIE reference laboratory cannot supply suitable vaccine candidates for both clades, they will assist the vaccine company to source the viruses from an alternative OIE reference laboratory.

Small quantities of ferret antisera for antigenic characterisation are available from the OIE reference laboratories in the UK and Ireland.

  • List of Participants

Representing the OIE reference laboratories

Prof. Ann Cullinane

Head of the Virology Unit

Irish Equine Centre

Johnstown, Naas

Co. Kildare


Dr Thomas M. Chambers

Maxwell H. Gluck Equine Research Center

Department of Veterinary Science

University of Kentucky

108 Gluck Equine Research Center

Lexington, Kentucky 40546-0099


Dr Armando Damiani

Institute of Virology

Veterinary Medicine

Free University of Berlin

Philippstrasse 13

10115 Berlin


Dr Debra Elton

Animal Health Trust

Centre for Preventive Medicine

Lanwades Park, Kentford

Suffolk CB8 7UU


Representing the WHO laboratories

Dr John McCauley
WHO Collaborating Centre for Reference and Research on Influenza
Mill Hill Laboratory
The Francis Crick Institute
The Ridgeway, Mill Hill
London NW7 1AA

Dr Nicola Lewis
WHO Collaborating Centre for Modelling, Evolution, and Control of Emerging Diseases
University of Cambridge

Other experts

Professor Xiaojun Wang
Harbin Veterinary Research Institute, CAAS
427 Maduan Street,
Harbin, 150001

Dr Takashi Yamanaka
Epizootic Research Center
Equine Research Institute
Japan Racing Association
1400-4 Shiba, Shimotsuke
Tochigi, 329-0412


Dr María Barrandeguy
Responsable del Laboratorio de Virus Equinos
Instituto de Virología

Dr Loic Legrand
Frank Duncombe Laboratory
1, route de Rosel
14053 Caen CEDEX 4

Dr Adam Rash

Animal Health Trust

Lanwades Park, Kentford

Suffolk CB8 7UU


Dr Nitin Vimani
Pcincipal Scientist
National research Centre on Equines
Sirsa road, Hisar 125 001 (Haryana)

Dr Rozanah Asmah binti Abdul Samad
Veterinary officer (Senior Assistant Director)
Department of Veterinary services,
Wisma tani, block podium 4G1, 62630 Putrajaya
Federal Territory

Dr Romain Paillot

Animal Health Trust

Lanwades Park, Kentford

Suffolk CB8 7UU