Defra confirmed the case today (Wednesday 3 October) and the horse will be put down.
Around 20 other horses on the yard have been placed under quarantine and are being tested.
EIA is a virus that attacks a horse’s immune system. It is passed by biting insects such as flies and can cause death, as well as mares to abort.
There is no cure, so horses confirmed with EIA are put down to prevent spread of disease.
It is the second time this week EIA has been in the news – on Monday (1 October) racehorse Danedream was pulled from this weekend’s Prix de l’Arc de Triomphe after a case was found at Cologne racecourse in Germany, where she is based, preventing her from travelling.