Tag Archives: bovine TB

Plan to cull badger cubs shows the cull’s not about bovine TB

The Guardian reported this afternoon that next year’s badger cull will start earlier, in June or July, when badger cubs will be young and inexperienced. This means they will be easier to trap and kill than cubs later in the year. This will help the cullers achieve their target numbers of badgers killed, but will not help them reduce bovine TB.

For badger culling to reduce the incidence of bovine TB in cows, the scientific evidence shows that a large proportion of badgers need to be killed. So far, the cullers have missed their targets. On the face of it, starting earlier in the year, when cubs are easier to kill, may help them. But in reality it’s likely to have little impact on the spread of the disease for two reasons:

  1. Many cubs die in their first year anyway, so shooting them will have less effect on the badger population than killing the same number of older badgers.
  2. Cubs are less likely to be infected with TB than adults, so aren’t the badgers that are most likely to spread the disease to cattle.

This provides further evidence that the cull is not really about reducing bovine TB – at best it’s about looking like they’re trying to reduce bovine TB. I realise this makes me sound like one of the crazy conspiracy theorists that abound on the internet. But, as discussed in previous posts (The badger cull: an ‘evidence to policy’ perspective; Badgering pays off at last) the cull so far has shown no signs of meeting the conditions necessary to have an impact on the disease. To carry on with it in the face of evidence from the government’s own advisory panel saying it’s neither effective nor humane, hints at the politics behind the cull. To then introduce further measures that are likely to increase the numbers of badgers culled without reducing transmission is a very cynical ploy.

Bovine TB is a big problem. But it doesn’t justify an expensive, ineffective, inhumane cull that has already cost the tax payer millions, and has little chance of making a difference. The government and National Farmers Union need to look at other ways to tackle the problem, rather than ignore or distort the scientific evidence.

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Badgering pays off at last!

Good news – the government has finally decided to listen to the  evidence and put a stop to plans to roll out the badger cull.
The pilot culls in Somerset and Gloucestershire aimed to see:
  • if culling using free shooting could kill enough badgers 70%) to reduce bovine TB
  • if it was a humane way of killing badgers
  • if it was safe
My previous blog post on the evidence for and against the cull discusses this. Suffice it to say, the pilot culls failed miserably on the first two criteria. It’s only success was that no-one was hurt.
Despite the overwhelming evidence on the failure of the pilot culls, the high costs and widespread public and political opposition to them, it was by no means certain that the government would pull the plug on the idea of rolling them out. The National Farmers Union have continued to push for them. But we now know they won’t be expanded to new areas.
The government have also announced a programme of vaccinating badgers around the edges of areas with high levels of bovine TB.
Badger
It’s not all good news for badgers, though.  Culling of badgers in the pilot cull zones will be allowed to continue, with no monitoring.  This seems bizarre, given the pilots found that closely scrutinised free shooting was inhumane. Unmonitored killing is hardly likely to be more humane. Obviously that no longer matters…
The culls have, from the start, been more about politics than evidence. I have no doubt that the decision not to expand the cull is mainly due to the campaigns against it, rather than whether the cull was likely to reduce bovine TB. Well done to all who campaigned against the cull, and the activists who monitored the cull.

The badger cull: an ‘evidence to policy’ perspective

Lots has already been written about the badger cull. There’s no dearth of emotive responses to it online. If you’ve visited my blog before, you’ll probably have picked up that I love wildlife. What you may not know is that, in my day job, I work on randomised controlled trials. More specifically, I work on translating the evidence we get from trials into policy and practice. So I’m trying to write this post with my ‘evidence to policy’ hat on.

Randomised controlled trials are the most reliable way of finding out if an intervention works. This short film explains why randomised controlled trials are important.

Outside of medicine, it’s rare for proper randomised controlled trials to be conducted to test if an intervention works. So the fact that a trial was conducted to test whether badger culling reduces bovine TB is a big deal. It means we have high quality evidence about the efficacy of badger culling.

So what did the Randomised Badger Cull Trial (RBCT) find?
The trial found that after 4 years of culling, bovine TB in cattle was reduced by 23% in the cull areas, but increased by 25% on the land less than 2km from the cull zone. It also found that localised reactive culls (where badgers are culled only after an outbreak of bovine TB) actually increased bovine TB in cattle.

Does this mean the current badger cull will help reduce bovine TB?
While it might initially seem that the evidence from the trial supports the current cull, it’s actually much more complicated. When working out whether the results are generalisable, (will apply in a different setting to the original research) we need to consider whether the intervention being used now is the same as that used in the trial.

In the RBCT badgers were culled by being trapped in cages then shot. This method is expensive, but it reduces the chances of badgers being missed, or being wounded and then escaping. The current cull is looking at free shooting, which hasn’t been trialled, and might not be so effective at killing badgers.

The proportion of badgers that are culled within an area is also important. In the trial, 70% of badgers in cull areas were killed. If the proportion killed is lower, it doesn’t simply mean there will be less reduction in bovine TB. This is because culling causes badgers to scatter further afield than they would otherwise (this is called perturbation), which, if they are infected with TB may actually result in increased transmission to cattle (as was found in the reactive cull areas, and those around the cull zone).

That’s why the pilot culls are important: we need to know whether free shooting is effective at killing enough badgers to make it likely that there may be a reduction in TB in cattle. Both pilot sites (Somerset and Gloucestershire) have been unable to kill the required proportion of badgers, and extensions to the cull periods have been applied for. The pilots have proven that free shooting cannot kill enough badgers quickly enough. This raises the risk that the culls may actually increase perturbation and therefore bovine TB.

What else needs to be considered when thinking about translating trial evidence into policy?

Cost-effectiveness RBCT found it wasn’t cost-effective. That’s why in the current cull they decided to go for free shooting rather than the more expensive trap and shoot used in the trial. The calculations were that it might be cost effective with this cheaper method. However, with the costs of policing the pilot estimated to run into millions, this now lookes unlikely. This is exacerbated by the apparent failure of free shooting to kill enough badgers. Failing to reach the target proportion of badgers culled increases the risk of the cull causing perturbance, which could increase bovine TB. To tackle this, there are reports that hundreds of cages have been brought in. This will increase the costs of the cull, and may well mean any benefits are outweighed by the monetary costs.

Feasibility: as well as considering whether an intervention is effective and cost-effective, policymakers need to consider whether it is feasible to implement it at the required scale and quality. The necessity of extending the length of the pilot culls would perhaps indicate that it is less feasible than anticipated.

Acceptability: clearly, given the keeness of the NFU to introduce badger culls, the intervention is acceptable to many farmers. It is equally clear that the measure is unacceptable to many in the general public, as evidenced by the number of signatures on petitions against the cull, and active protests around the country. It doesn’t look like a compromise is likely to be possible.

Need: bovine TB is a major problem, costing the UK £90m last year. Farmers and DEFRA argue that this means something must be done. However, it doesn’t make sense to argue that because something must be done we must do something that is likely to be ineffective (and probably harmful to the cattle who we are aiming to protect), and where the monetary benefits are outweighed by the monetary costs. We need to find ways to tackle bovine TB, but that doesn’t mean we should ignore the evidence on the likelihood of effectiveness and costs of any strategy.

Risk: a first principle of medical interventions is ‘first, do no harm’. The scientists who carried out the RBCT have come out strongly against the cull, saying it is not supported by the evidence, and is more likely to do harm to cattle than good.
Wiping out large numbers of badgers is likely to have effects on other animal species as well. We have to be careful when messing with the natural foodchain, as changes in the numbers of one species affect many other species. Reduced competition from badgers may well lead to an increase in other species, such as foxes, who aren’t too popular with many farmers either.

Ethics: badgers are protected by law. They are living creatures. One of the aims of the pilot cull was to assess the humaneness of free shooting as a method of killing badgers. It has now been admitted that it is unlikely to be able to tell us this. There is even talk of gassing of badgers in their sets, despite this having been outlawed 3 decades ago for being inhumane.

If we, as a society, are consciously going to wipe out large numbers of any of our native species, we need to be very sure it will have the effect we want. I believe the current evidence does not stack up. The cull is unlikely to significantly lower incidence of bovine TB, may actually increase it, and will cost more than the benefits are worth. We need to tackle bovine TB, but this is not the way.