TB eradication must be 'science led' - MP



CLA President William Worsley said: "I am very impressed by the Government’s brave decision to tackle this appalling disease head on. For too long, the scientific advice and escalating costs of Bovine TB have been avoided by politicians.

"Farm businesses have been devastated, communities disrupted and markets distorted by the ineffective handling of Bovine TB by the previous administration.

"There will be relief all round that there is now political will to combat this disease. A cull will form part of a package of measures. It is not about eradicating British wildlife unnecessarily."

Comments

16-09-2010 21:51 PM | Posted by Anonymous
The government's badger culling plans are about as "science led" as intelligent design. William Worsley talks of science, but joins the list of those who talk about the need for a cull without citing a single piece of evidence that it would be effective.

If such plans were really science led, maybe politicians would look first for whether cattle based measures are proving effective. The relevant figures can be found on DEFRAs website, here:
http://www.defra.gov.uk/foodfarm/farmanimal/diseases/atoz/tb/stats/county.htm
Here they would find that in Wales, 3.2% of new herds were found to be infected in 2009, compared to 4.4% in 2008. In England a similar pattern is evident, with a drop from 5.5% to 5.0%.
Those with statistical training might wonder if these patterns are statistically significant, i.e. whether these results might be the result of chance variation in the herds that happened to be tested. As it turns out, there is only a 0.5% chance a drop this extreme would have been observed for England if there were no underlying difference, and a miniscule 0.000005% for Wales. So the answer is "yes", these figures indicate a genuine drop between 2008 and 2009, and that cattle based measures are working.

If this were not the case our hypothetical science-led government might then ask whether there is any evidence that badger culling would improve the situation. The Independent Science Group, led by an expert on both badgers and epidemiology, Rosie Woodroffe, based on the large scale Randomised Badger Culling Trials (RCBT), concluded that badger culling could make no meaningful contribution to cattle TB control in Britain. Admittedly the UK chief scientist David King decided to write his own report on the same evidence concluding the opposite, but he was strongly criticised in the journal Nature, and one can only think that as a physical chemist, he was somewhat "off his own turf" in terms of expertise here.

Imagine that there was some evidence that a badger cull could work. Even now our actual government's culling plans look like a recipe for disaster. As far I can see, it is up to farmers themselves to shoot or vaccinate badgers. I am all fine with the vaccinating badgers part, but I would imagine that the shooting option is cheaper, and so this is what most farmers will do. Whilst I am pleased that my taxes will not pay for this hair-brained scheme, and that people against the cull will not be forced to have badgers exterminated on this land, as would have happened with the Welsh Assembly's plans, the government clearly has not thought about what the science says about this either.

Studies have found that TB incidence in badgers actually increases as the result of repeated culling (Woodroffe et al 2006 Proceedings of the National Academy of Science 103: 14713-14717). This seems to be because disrupting the population structure causes badgers to move, which in turn prevents spread of the disease. This same effect is thought to be responsible for the increase in TB in cattle that was found in the RCBT in areas bordering culling zones.

So just a moment's thought suggests that the government's plan to allow farmers to cull badgers is likely to be catastrophic. Some farmers will cull, some will not, either because they have a grasp on how unlikely it is to have an effect, or they cannot afford it. Some farmers are likely to attempt a cull, but fail to reduce badger numbers meaningfully. This patchwork pattern is likely to be a recipe for huge levels of badger movement, and an associated rise in the national levels of bTB. So keep an eye on those DEFRA figures, because they are likely to start rising.

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