Swamp fever is not transferable to humans but is fatal in equines. If an infected horse does not die, it will carry the disease for life and faces indefinite isolation or compulsory euthanasia.
It causes intermittent fever, anaemia, emaciation and death.
The horses were imported into the country from Romania via Belgium on 22 December. They arrived in a group of 10 horses, nine of which originated from Romania and one from Belgium.
Defra has confirmed the horses are being destroyed.
The horses were not displaying signs of swamp fever, but tested positive for antibodies to EIA during routine post-import testing.
The premises in Wiltshire on which they were kept has been isolated, and work is urgently being carried out to trace what other animals have been in contact with the infected horses since they entered the country.
The seven other horses they travelled from Romania with have tested negative, and tests are currently being carried out on the horse from Belgium.
EIA or swamp fever is spread via blood contact and biting flies — so vets are hoping the cases will have been contained.
But the news is likely to be a huge worry for the entire British horse industry. In 2006, Ireland’s equine and bloodstock industry was crippled when an outbreak of EIA spread through the country.
Defra’s chief veterinary officer Nigel Gibbens said; “The last case of EIA infected animals being imported into Great Britain was in 1976. These were apparently healthy horses carrying a notifiable disease that we are keen to keep out of the country.
“After considering the risk, I have decided to take appropriate action and humanely destroy these two horses that tested positive.”
The disease has also been found in recent years in both Italy and Germany, but it is endemic in Romania — which joined the EU on 1 January 2007 — where there may be up to 16,000 cases at any one time.
Read the facts about swamp fever.