Britain鈥檚 foot and mouth epidemic is beginning to fizzle out, but the scientific post mortem has already begun into how the crisis was handled.
There are now about five new outbreaks per day, compared to 40 per day at the peak of the crisis in early March. So far, there have been 1575 outbreaks, and 2.6 million animals slaughtered.
But not everyone is happy with the severity of the measures that achieved this reduction, or the scientific rationale behind the measures.
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The Veterinary Record published on Friday impassioned letters from vets critical of the government鈥檚 draconian slaughter policy. There are also two scientific papers in the journal suggesting that many healthy animals could have been spared.
The correspondents say that in deciding on its policy, the UK government appeared to sideline vets and give undue weight to the advice of mathematical modellers.
On the modellers鈥� advice, the government introduced in late March a 鈥渟laughter on suspicion鈥�. This meant taking no longer than 24 hours following an alert to kill all animals at a suspected outbreak.
Secondly, vets were asked to kill within 48 hours all the animals up to three kilometres away, a so-called 鈥渃ontiguous cull鈥�. But many vets and farmers were uneasy about the policy because it meant killing so many healthy animals.
Figures released on Thursday by the government give weight to these concerns. They showed that blood tests from outbreaks were negative in 29 per cent of cases, suggesting that the animals may have been culled unnecessarily.
鈥淧olicies in the present foot-and-mouth disease outbreak seem to be dictated by politicians and scientists, not vets in the field,鈥� says K.M. Wood, a vet from Stroud in Gloucestershire.
鈥淭he widespread slaughter of healthy animals which we have been forced to witness 鈥� must never be allowed to happen again,鈥� says Sarah Binns, a vet from Somerset.
The two scientific papers by veterinary scientists at the Institute for Animal Health鈥檚 laboratories in Pirbright, Surrey give weight to these arguments. Both show that the strain of virus causing the outbreak is much less likely than expected to spread on the wind. This suggests the ruthless contiguous culling may not have been required to stamp out the epidemic.
The first paper concludes that pigs are very resistant to airborne infection. The second calculates important differences in the likelihood of airborne spread depending on which species of animal is infected, and the size of the herd.
鈥淲ith sheep or cattle farms, unless there are thousands of infected animals, it probably wouldn鈥檛 spread more than a few hundred metres,鈥� says Soren Alexandersen, one of the authors.
He and his colleagues conclude that sheep should be culled on farms neighbouring an outbreak. But careful surveillance would be sufficient if adjacent farms only had cattle or pigs.
Alexandersen stresses that the conclusions don鈥檛 allow for spread by physical contact between animals, or by contamination from vehicles or people. But he wonders why the mathematical modellers didn鈥檛 factor the important species differences into their models.
Hitting back, the modellers say that it鈥檚 unfair to criticise with the benefit of hindsight. They also reject the idea that vets were sidelined. The modellers say that the 鈥渃ontiguous cull鈥� order was 鈥渞efined鈥� three weeks ago to give vets more discretion over whether a cattle herd was infected.
鈥淚f, on the basis of the new findings, there are good scientific grounds for refinement, that鈥檚 all well and good,鈥� says Mark Woolhouse, of the University of Edinburgh, one of the key modellers advising the government.
鈥淏ut unfortunately, no-one had that information at the beginning of the epidemic,鈥� he says.
Woolhouse admits that contiguous culling is a 鈥渂lunt instrument鈥�, but he defends its introduction. 鈥淎 very large number of cases are in farms neighbouring outbreaks 鈥� you can see it in any of the maps,鈥� he says. He adds that animals killed through the contiguous cull account for a small fraction of the total.
