Quarantine regulations have been lifted on the Wiltshire yard where swamp fever was found in January.
Two horses were culled immediately and another 50 horses put into isolation after the outbreak, in horses imported from Romania, through Belgium.
Now after three sets of tests for the disease — also known as equine infectious anaemia (EIA) — at 30-day intervals, the premises have been declared free of the disease by Defra.
No further horses tested positive for EIA in that 90-day period.
EIA is an untreatable disease believed to be spread by the exchange of bodily fluids, including by insect bites.
Affected horses remain infectious carriers for life, and must be euthanased.