Faster cull 'could have saved many animals'

A million animals slaughtered during the foot-and-mouth epidemic could have been saved if an effective culling policy had been enforced earlier, according to scientists who have carried out the most detailed analysis yet of the epidemic.

Almost a third of the 3.9 million cattle, sheep and pigs destroyed to date would still be alive if the current slaughter policy had been enacted from 1 April instead of a haphazard introduction more than a month later, the scientists said.

Two independent groups of researchers using different mathematical models have found that the existing policy of slaughtering all animals on infected premises within 24 hours of a reported outbreak and all animals on contiguous premises within 48 hours is the most effective way of controlling the spread of what is the most infectious agent known to science.

"This is the most thorough analysis yet of the epidemic," said Professor Neil Ferguson of Imperial College in London, who led one of the studies, published in Nature, analysing how the world's worst foot-and-mouth epidemic was eventually brought under control.

"It has enabled us to evaluate the different policies in turn and it clearly shows the need for a rapid and complete contiguous culling policy for disease control and eventual elimination," Professor Ferguson said.

Whether it was possible for government officials to put the policy in place earlier than they did is another matter but Professor Ferguson believes they could have "got further than they did".

He said: "Part of the reason we needed such a drastic culling policy was that we failed to diagnose the presence of the disease early enough."

A second group of researchers, publishing in the journal Science, also found that the epidemic could have been brought under control sooner if 24/48-hour culling had been introduced earlier. The team concluded that prompt culling was more effective at tackling a widespread foot-and-mouth epidemic than vaccination.

Matt Keeling of the University of Cambridge, who led the research team , said the nature of British farms explained why it had taken such a long time for the epidemic to tail off.

"The model of the epidemic we have developed shows that the size and species make-up of farms has been a significant factor in the epidemic, with more infection on larger farms," Dr Keeling said.

The research team – whichincluded scientists from the Government's Veterinary Laboratories Agency and Edinburgh University – found that fragmented farms made up of scattered fields, which are common in Cumbria, the centre of the epidemic, are at much higher risk than contained farms. "Cattle farms are the most susceptible to infection, followed by sheep farms and pig farms," said Dr Keeling.

Both teams of scientists warned that any relaxation of the restrictions on animal movements or sterilisation procedures in affected areas runs the risk of reigniting the epidemic and prolonging it by many more months.

Christl Donnelly of Imperial College said the lessons of the last major foot-and-mouth outbreak in 1967 showed it was important not to relax these restrictions even when the epidemic appeared to be snuffed out. "As the weather gets cooler and the virus is able to survive longer, we are in danger of seeing significant outbreaks of the epidemic again," Dr Donnelly said.