Foot-and-mouth is a highly infectious viral disease in cloven-hooved animals, cattle, sheep, pigs and goats. Horses are not affected. Some wildlife can spread the disease. While it seldom kills these animals, they develop blisters on their feet and mouths, and sometimes on their teeth, lose weight and show signs of depression.
The animals become lame, and there is increased salivation, according to Mr Sean O'Laoide, of Veterinary Ireland, which represents Irish veterinary practitioners.
The disease, he said, could cause havoc, because it was highly contagious and could be spread in the air, by humans who had contact with diseased animals, in animals' bodily wastes, or in milk or cheese. It could also be passed by contaminated clothing or footwear or by using equipment such as vehicles or holding facilities.
EU regulations require the destruction of animals which contract foot-and-mouth. A plan to vaccinate against the disease was dropped some years ago. The advent of the single market, allowing freedom of movement inside the EU, has added to the difficulties of stopping the spread of such diseases.