Influenza: are we protecting our horses effectively?

In the UK, a mandatory flu vaccination policy was introduced by the Jockey Club in 1981. The fact that since then no single day's racing has had to be abandoned is often quoted as evidence that this programme is effective. However, flu is still diagnosed in horses that have been vaccinated. That is not to say that flu vaccines should be abandoned: the majority of outbreaks in vaccinated groups of horses are of limited size and vaccination reduces the occurrence of epidemics.

Flu viruses frequently mutate so that they become unrecognisable to the immune system: this is called antigenic drift and means strains in flu vaccines go out of date. The World Organisation for Animal Health (OIE) is responsible for recommending suitable vaccine strains for inclusion in commercial vaccines and decision making is informed by ongoing surveillance data provided from numerous centres across the globe, including in the UK from the Equine Influenza Programme (http://www.equiflunet.org.uk/). This programme is funded by the Thoroughbred racing industry via the Horserace Betting Levy Board.