Horse owners have been warned to be vigilant after two more cases of deadly swamp fever were diagnosed in the UK.
In January equine infectious anaemia (EIA) was discovered in two horses in Britain for the first time in 34 years. Now a horse in Northumberland and another in Devon have also been discovered carrying the disease. All of the animals originated in Romania.
A severe outbreak might prove to be the equine equivalent of the 2001 foot and mouth epidemic, which claimed the lives of 10 million sheep and cattle and cost the country an estimated £8bn.
Last night Nigel Gibbens, the chief veterinary officer at the Department for Environment, Food and Rural Affairs (Defra), said: "The threat of EIA to UK horses remains low but we take it seriously and urge owners and vets to notify us of any suspicion of the disease.
"Since the first outbreak this year we have worked hard with the EU to proactively reduce the risk to the UK, and exports of horses from Romania are now severely restricted, along with more UK import testing. We believe the cases in the UK this summer relate to horses that left Romania before these measures were in place."
Swamp fever, so called because it typically occurs in marshy areas, is a notifiable disease and Defra urged horse owners and vets to notify their local Animal Health office if they suspect an infection.
As the disease is carried by biting flies, all other animals that have been within a 200 metre radius of the affected creature are quarantined for 90 days. It can also be passed on by vets using dirty syringes and other infected medical equipment.