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Britain's dramatic battle against foot-and-mouth disease (FMD) appears to be paying off. Since the government stepped up its control measures last month, the daily number of newly infected farms has been dropping, and some researchers predict that the epidemic may be past its peak. So far, FMD has been found at 1341 British farms.
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Funeral pyre. Over a million livestock have been killed in Britain to control FMD.
CREDIT: MURDO MACLEOD/CORBIS SYGMA |
The British government stepped up its control measures after it received a grim warning from epidemiologists in late March. Researchers at the Ministry of Agriculture, Fisheries, and Food (MAFF), the University of Edinburgh, Imperial College in London, and the University of Cambridge had each produced computer simulations of the outbreak, fed with epidemiological data provided by MAFF. Their models clearly showed that Britain's attempts to control the disease weren't working: The epidemic was still growing exponentially, and, if nothing changed, would spiral out of control.
The problem, the researchers said, was that as many as 3 or 4 days typically elapsed between the identification of an infected farm and the slaughter and destruction of its herd. That delay enabled the fiercely infectious virus to spread. At a joint meeting of the ministry and the Food Standards Agency on 21 March, scientists also argued that "ring culling" at farms adjacent to each infected farm--even if the animals there appear healthy--was necessary to halt the outbreak. (Science published the computer simulations of one group, led by Imperial College's Neil Ferguson, online last week.)
In response, the government adopted a more aggressive campaign. Now, with the help of the army, most infected herds are culled within 24 hours--more than 1.1 million livestock have already been destroyed--and ring culling has become standard. The studies "certainly had more of an immediate impact than any previous mathematical model of an infectious disease," Ferguson says. And the strategy seems to be working: Between 8 and 15 April, there were an average of 27 new confirmed cases each day, compared to 32 in the week before, and 45 late last month.
Still, says study leader Mark Woolhouse of the University of Edinburgh, it's too early to be certain that the current decline really marks a turning point in the epidemic. He notes that aggressive ring-culling would always reduce the number of new cases--because some of those farms undoubtedly housed animals that were infected though asymptomatic--but the outbreak could bounce back. "Let's wait a while to see how well we're doing," Woolhouse says.
--MARTIN ENSERINK
Related sites
The Ministry of Agriculture, Fisheries, and Food, with the latest on FMD
Science background story on foot-and-mouth disease, 23 March
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