An outbreak of equine herpes (EHV-1) has been confirmed by vets in Devon.
The Animal Health Trust on Tuesday (2 July) confirmed the neurological form of the disease at the property in North Devon.
Two thoroughbred mares were put down at the yard last week (28 June) after testing positive for the infection.
Control measures have been put in place, including restricting movement of 180 horses.
The outbreak has also been linked to the EHV-1 case found on 28 June in Warwickshire, as the affected thoroughbred mare had moved from the Devon site 16 days earlier.
Tests have come back negative from other horses at the Warwickshire premises but further lab results are still being waited for.
EHV-1 causes outbreaks of fever, respiratory problems and paralysis as well as causing mares to abort.
It is spread by direct horse-to-horse contact, most commonly through the respiratory system.