A comparative antibody study of the potential susceptibility of Thoroughbred and non-Thoroughbred horse populations in Ireland to equine influenza virus.
BACKGROUND
In Ireland, horses may be protected against equine influenza virus (EIV) as a result of natural exposure or vaccination. Current mandatory vaccination programmes are targeted at highly mobile horses. A correlation between antibody levels as measured by single radial haemolysis (SRH) and protective immunity against EIV has been established.


OBJECTIVE
The objective of this study was to determine the susceptibility of selected populations of horses by quantifying their antibodies to EIV.


METHODS
Blood samples were collected from Thoroughbred weanlings, yearlings, racehorses and broodmares, teaser stallions and non-Thoroughbred horses. Antibodies against EIV H3N8 and H7N7 were measured by SRH.


RESULTS
The order of susceptibility to Equine Influenza (EI) in the populations examined in Ireland was as follows: Thoroughbred weanlings > teasers > non-Thoroughbred horses and ponies > Thoroughbred yearlings > Thoroughbred horses in training > Thoroughbred broodmares. The H3N8 antibody levels of the weanlings, yearlings, broodmares and horses in training were similar to their H7N7 antibody levels, suggesting that their antibodies were primarily vaccinal in origin. The teasers and non-Thoroughbreds had higher H3N8 antibody levels than H7N7 antibody levels, suggesting that the majority of seropositive horses in these populations had been exposed to H3N8 by natural infection.


CONCLUSIONS
Weanlings, teasers and non-Thoroughbred horses were identified as most susceptible to EIV. The results suggest that it would be advisable that weanlings are vaccinated prior to attendance at public sales, that teaser stallions are vaccinated prior to each breeding season and that mandatory vaccination be implemented for participation in non-Thoroughbred events.
Virology Unit, The Irish Equine Centre, Johnstown, Naas, Co. Kildare, Ireland.
Sarah
S
Gildea
Sean
S
Arkins
Ann
A
Cullinane
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D005260:Female; D006734:Horse Diseases / Q000276:immunology* / Q000517:prevention & control*; D006736:Horses; D053123:Influenza A Virus, H3N8 Subtype / Q000276:immunology*; D053126:Influenza A Virus, H7N7 Subtype / Q000276:immunology; D007494:Ireland; D008297:Male; D009976:Orthomyxoviridae Infections / Q000276:immunology / Q000662:veterinary*
D000914:Antibodies, Viral