In the spring of 2001, the UK countryside turned into a crematorium. A foul-smelling haze settled over parts of the country as 6m cows, sheep, pigs and goats were slaughtered and their carcasses burned in the fields. This was the result of a bid to control an outbreak of foot-and-mouth disease – a contagious disease of livestock named after the ulcers it causes in the mouth and between the hooves of farm animals.