London

Early delays in tackling foot-and-mouth disease undermined the British government's attempts to control the outbreak, according to three epidemiological studies. All of the studies find that the epidemic is now out of control in the United Kingdom.

Animals at a farm near Newcastle in the north of England were almost certainly infected with the disease in early February, but the outbreak was not detected until sheep were moved over 400 kilometres to an abattoir in Essex. By the time full restrictions on the movement of animals were imposed on 23 February, transport of animals infected at the farm and abattoir had spread the disease across the country.

Teams from Imperial College, London, the University of Edinburgh and the government's Veterinary Laboratories Agency (VLA) in Surrey conducted separate studies on the basis of available government data.

“We're still in the exponential stage of the outbreak,” says Mark Woolhouse, an epidemiologist at the University of Edinburgh (see Commentary on page 515).

The three studies make different predictions for the epidemic's development in the medium term. The VLA offers the most pessimistic scenario, projecting 4,411 cases by the end of June. At the other end of scale, the Edinburgh team estimates that 918 cases will be recorded by July — 627 cases had been confirmed by 27 March. Neither team was able to say when they thought the disease would be wiped out.

Out of control: culling is on the increase as foot-and-mouth spreads out across Britain — and Europe. Credit: MURDO MACLEOD

The government is now trying to limit the spread of the disease by culling all animals within 3 kilometres of infected premises in areas where the virus is widespread — a move that may result in the slaughter of some 600,000 animals.

Far smaller outbreaks have been confirmed in the Republic of Ireland, France and the Netherlands. Dutch vets have got permission from the European Union to vaccinate all animals in a 10-kilometre ring around the outbreaks, although the Dutch government says it will vaccinate only if it cannot slaughter all the infected animals quickly enough.

Despite calling in the Army to help dispose of culled animals, Britain now faces exactly such a backlog, leading some epidemiologists to suggest that vaccination might be useful. It had previously been ruled out because many countries will not accept meat imports from vaccinated areas.

Epidemiologists instead suggest cutting the interval between identifying and slaughtering infected animals. The gap averaged two to three days at the start of the epidemic, but the Imperial group says reducing this by a day could almost halve the total number of cases.