Foot-and-mouth disease study could save millions of animals
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A paper out today in the journal Science could save the lives of millions of cattle, sheep, goats and pigs.
Researchers in the United Kingdom have proven that the infectious period for foot-and-mouth disease is only 1.7 days on average, rather than the four to eight days previously believed.
That number means that when an outbreak of this disease hits, the number of animals that need to be 'culled' because of possible exposure could be much, much lower.
An outbreak of food-and-mouth in the United Kingdom in 2001 resulted in the culling of 6 million cattle and sheep, even though only 2 million actually were infected with the disease, according to a report by the government of the United Kingdom. The outbreak cost $13 billion dollars. At its height, over 100,000 animals were being slaughtered a day.
The strategy to stop foot-and-mouth epidemics is much like stamping out a grass fire, says Will Heuston, a director of the Global Initiative for Food Systems at the University of Minnesota.
"You get in as quickly as possible and you try to remove those animals that might expose others." That's meant strategies of preemptive culling, which ends up meaning the number of animals culled "far exceeds the number that are actually ill," he says.
The experiments done by the researchers a the Institute of Animal Health in Surrey and the Center for Immunity, Infection and Evolution at the University of Edinburgh may change all that, says Mark Woolhouse, the senior author on the study.
The researchers took pairs of cows, one infected and one not, and placed them together for eight hours at a time to find the actually period during with infected cows were infectious.
What they found, to their surprise, is that a cow is infected for longer than can infect others. And even more importantly, there is "a short window of time, just a day or two, where we can tell that a cow is infected with hoof and mouth disease but it can't infect other cows," says Woolhouse.
That period could mean that intensive monitoring of herds for foot-and-mouth disease could detect outbreaks early.
"If we could detect and remove animals during that window of opportunity then they won't have the chance to infect any other animals. And that means that there wouldn't need to be preemptive culling," says Woolhouse.
Of course those tests are much easier to do in the laboratory than in the field and present a "formidable logistical challenge," he says. "There's a lot of work to be done," but it does appear possible.
The researchers have been able to detect the virus in blood and nasal swab samples of cattle and think they may be able to detect it in airborne samples as well. They're also looking at whether the virus appears in milk before a cow becomes infectious.
Food and mouth disease can't be transmitted to humans but is a devastating disease for the animals, killing some and leaving others debilitated and sickly for life.
The culling is horrific not just because of the cost to the animals and the farms but also to their human owners. The strategy makes logical sense for at the national level, but is "gut-wrenching," says Heuston. Farmers with enormous emotional attachments to their animals have to watch healthy animals taken off to be killed. "They had farmer suicides (in Britain)," he says.
The United States stamped out food-and-mouth disease in 1929 and has had no cases since then. However the disease remains in Europe Asia, Africa and South America. But news of the finding from the United Kingdom is welcome here, too.
"It's not a question of if it returns, but when -- and we want to make sure that when it happens it's not the sky is falling, that we know what strategies we need to put into place," says Heuston.
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