Foot and mouth is so called because the most visible signs of infection are vesicles, or blisters, on those parts of the body. These heal after a few days but, in the long term, the disease can cause reduced milk yields and weight loss in animals. In a minority of cases, mostly among very young or old animals, it can prove fatal. (Humans are rarely affected. During the 1967 epidemic, one person contracted the disease. At the time of going to press, the number of suspected human cases in the latest outbreak had not reached double figures.) The highly contagious virus is present in large quantities in fluid from the blisters as well as an infected animal's saliva, milk, dung and breath. It ca be transmitted over long distances by air, and carried on the wheels of vehicles. The cold, wet weather has helped it spread, as the virus survives longer in these conditions.
Vaccination is expensive and gives protection for only around six months, during which time animals can act as carriers of the disease. Most countries will not import animals which have been vaccinated and it is difficult to detect which animals have been inoculated. The best way of stopping the spread of the disease is to isolate farms, stop animal movements, cull those affected and others within an exclusion zone and destroy the carcasses.
By the middle of April, almost 1.2 million animals had been slaughtered and almost 600,000 were awaiting slaughter. During the 1967 outbreak, which was concentrated around Cheshire, Shropshire and north Wales, there were 2,364 outbreaks and 442,000 animals were destroyed. The 1967 outbreak was mainly among pigs and cattle, and geographically concentrated. This time, sheep have also been infected, and improved road links have allowed the disease to spread faster and further.