Nigel Williams reports on some of the challenges facing a committee considering the scientific aspects of the fall-out of a devastating British epidemicA new committee met for the first time this month to consider the scientific aspects of infectious diseases of livestock and what can be gleaned from Britain's handling of this year's devastating outbreak of foot and mouth disease. The inquiry, launched by Britain's science academy — the Royal Society — comprises farmers, environmentalists and consumers alongside scientific experts, highlighting the importance of considering wider interests in assessing the scientific issues. The committee, headed by Brian FollettBrian Follett, is one of three announced by the government this summer in response to the crisis which may herald a major overhaul of policy on agriculture and the countrysidecountryside.Fig. 1Seeking answers: Sir Brian Follett, chair of the new Royal Society committee on infectious diseases, hopes their work will throw new light on the scientific issues.View Large Image | View Hi-Res Image | Download PowerPoint SlideFig. 2Beware: A notice informs the public about restricted access to land in the wake of this year's outbreak of foot and mouth disease. Access to the British countryside was heavily restricted with serious consequences beyond the agricultural community for many rurally based businesses.(Picture: Science Photo Library)View Large Image | View Hi-Res Image | Download PowerPoint SlideThe virus was first reported in Britain in early February. On February 23, the government imposed restrictions on farm animal movements, blocked public access to the affected regions and introduced the use of disinfectant for clothing, boots and farm vehicles. The first culls were restricted to infected farms or cattle sheds and those animals that had made ‘dangerous contacts’. With help from the army, the culling policy was strengthened in late March, and the epidemic reached its peak in April. By mid September, 3.88 million animals had been killed and the cost of the epidemic was estimated to be almost £5 billion.And the outbreak is not yet over. “I believe that we are in the final stages,” says David King, the government's chief scientific adviser, “but there is no room for complacency”. There may be old disease among a few flocks of sheep that could suddenly be stirred up into new local epidemics and the peak autumnal movement of livestock has to be controlled, he says.One of the key controversies facing the new committee will be the scientific case for the pursuit of a policy of culling without any use of vaccination in an attempt to control the disease. The massive pyres of burning carcasses caused public horror and helped put off many potential tourists to the country. The public would not tolerate new mass culls of livestock because of foot and mouth disease, the government's countryside adviser, Ewan Cameron, chairman of the Countryside Agency, has warned.In contrast, Argentina contracted foot and mouth disease about the same time as Britain in February. By April, the agriculture minister, Marcello Regunaga, decided to introduce a wholesale vaccination policy. Vets are in the process of injecting cattle and sheep on 200 000 farms, in a twice-yearly exercise which will cost $1 per animal.The Netherlands has also used limited vaccination to halt the spread of the disease — although vaccinated animals have subsequently been slaughtered. Adme Osterhaus, a Dutch virologist and European Union adviser, says that while there should be a cull at every foot and mouth outbreak, a second outer ring of vaccination would act as a buffer zone to prevent the disease spreading. “We know the vaccine will only be effective after a number of days so the first culling strategy will always be very important,” he says.One of the factors that drove British policy is the cherished foot and mouth ‘disease-free’ status for its national stock which helps allow movement of animals and animal products into world markets. Many within the agricultural community have seen this goal as paramount. King has written in the Daily Telegraph that “Mass vaccination, which would involve more than 40 million animals, does not completely remove the virus. Those animals that are incubating the disease when vaccinated will still become infectious. And vaccinated animals can still carry the virus, and may be infectious to other animals. The virus can live in the tissues of their throats for some time,” he said.And there are other problems many people see with vaccination. Nationwide mass vaccination does not necessarily stop the disease spreading from generation to generation. Mothers can pass antibodies to their offspring through their early milk. This gives temporary protection but, at the same time, interferes with the young animals’ immune response. Because of this, it is difficult to vaccinate young animals successfully, and leaves them vulnerable to disease. This prolongs the period over which the virus can continue to persist.“Mass vaccination would make it impossible to tell the extent to which the virus is present in the country's livestock,” says King. “There are no internationally recognised tests that are able to distinguish between vaccinated and infected animals.”Details of the spread of the epidemic have provided researchers with a rich source of data with which to model the disease and help inform policy decisions. More vigorous killing of sheep and cattle at the start of the foot and mouth epidemic could have cut the total number of cases by 16% and ended with 30% fewer slaughtered animals, according to a team of epidemiologists and statisticians from Imperial College London led by Neil Ferguson. Some parts of central England and south-west Wales — so far unaffected —are still at high risk, the model suggests.The researchers see no date for an end to the epidemic, the first since 1967. But they stress that there are dangers in the coming months, if controls are relaxed as temperatures fall. “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,” says Christl Donnelly, one of the team.The team studied the speed of the epidemic and the pattern of pasture holdings, and concluded that the swift spread of the disease followed the movement of animals, people or vehicles from farm to farm. Measures to contain the disease slowed the spread, but could not reverse it. However, the culls were essential, the team says — but in no week of the epidemic did the authorities meet the targets for culling all the animals at risk on neighbouring farms within 48h of report of a case. The epidemic “could have been reduced in scale had the control measures been rigorously applied earlier.” A separate study led by Matt Keeling at the University of Cambridge has also found that a speedier response at the beginning of the outbreak could have reduced its severity. At an angry inquiry opened in Devon this month farmers were critical that proposed restrictions on animal movements were given with four days’ notice, potentially allowing a widespread movement of infected animals around the country which could have led to the initial large scale of the outbreak. Follett hopes that the new committee can help throw new light on these issues.Says King: “We knew that this outbreak could have a long tail. But we have grounds to be cautiously optimistic. The current outbreak has been dominated by the disease in sheep. Blood tests conducted on more than 700 000 sheep in areas that formerly had the disease have shown that the vast majority of animals are healthy.”The new committee faces a challenge to see if scientific insights can help to avoid a repeat of this year's devastating events.