A Buckinghamshire yard is in quarantine after one of its horses was found to have the disease contagious equine metritis (CEM).
Defra has confirmed that the infection was detected on 22 October.
The government department would not release further information except that one horse has the infection and control measures in line with the Horseracing Levy Board codes of practice have been put in place.
CEM is a notifiable disease, meaning an outbreak must be reported to Defra. It can lead to infertility and cause a mare to abort her foal.
The disease brought the US breeding industry to a standstill earlier this year with around 711 horses in 46 US states either proving positive for the infection or put into quarantine after having been in contact with an affected horse.
Earlier this year a top vet said the UK is ripe for a full scale outbreak of CEM.