Sunday, October 13, 2013

More models, more spin.

Still torturing the 'rough assumptions' made in the RBCT Badger Dispersal Trial, 1997 - 2006 another piece of information is released this week, which has the BBC Badger Benefit Corporation in its usual mode.

Spin, more spin and extraordinarily selective reporting, now doing the rounds of social media.

 Professor Christl Donnelly of Imperial College has booted up her computer (link) again and fed it various data from the RBCT, obtained prior to 2006. The extruded headline announced that around half of zTB outbreaks in cattle are directly linked to badgers. The paper comments:
There is considerable uncertainty around this estimate [of 52 per cent], but the authors say that 38 per cent is a robust minimum value for the estimate. There is no robust maximum value.
It may be pedantic to point this out but actually, there is no uncertainty at all. Solid data was available then and is still available from AHVLA (Animal Health and Veterinary Laboratories Agency)  in the form of detailed risk assessments of all new herd breakdowns. Known as TB99s these were ignored by the modelers who preferred to input their own data as described in 7:24 of the Final Report where they explain:
The infection rate concerns all sources of infection for cattle, local infection for example across farm boundaries, infection from animals bought, in particular but not only, from high incidence areas and infection from wildlife, especially badgers.

All these are important but their relative importance, and that of cattle-to-badger transmission, cannot be estimated directly. In the following calculations, we assume all three sources to be roughly equally important."
Excellent. Hours spent painstakingly filling in risk assessments and the ISG prefer to make a rough assumption of equal importance using two parts cattle to one part badger? And they call that 'science'.

This is a chart of the RBCT assumed 3 way split:

But the actual figures from parts of the South West were extrapolated by AHVLA staff at the time and they tell a different story altogether.


You'll have seen these charts but they do bear another viewing, if only to knock on the head modeled  'rough assumptions' masquerading as 'new data'.

Predictably, the media is split with this story.

Some newspapers. such as the Independent (link) quite helpfully trot out the headline of over 50 per cent responsibility attributed to badgers, as does the PubMed journal, (link) PlosOne.

But never failing to disappoint, the BBC - (link) fix on the figure of 94 per cent and just like their mythical vaccination efficacy figure of 74 percent - (link) have bounced it around the networks.

If for one second, the mathematical models are unplugged and the actual situation examined, as Owen Paterson did in 2003 /4 , a completely different picture emerges. The Parliamentary Questions on which this site rests come in useful occasionally and although they make this post a tad long, we will repeat the answers of what really happens when a wildlife reservoir in badgers is successfully removed.

Owen Paterson teased many epidemiological points out of reluctant Minister, and they are archived in our 2004 postings. They include this gem concerning the success of the Thornbury badger clearance which lasted from December 1975 to August 1976 only. Then the Ministry officials walked away and the badgers were allowed to recolonise, soon reaching pre cull levels. Owen asked for the result of Thornbury on cattle herds:
"No confirmed cases of tuberculosis in cattle in the area were disclosed by the tuberculin test the the ten year period following the cessation of gassing" [150573]
So not 20 years of buggering about trying to cull out infected badgers in ones and twos, very occasionally as done by the RBCT? Or even taking indiscriminate pot shots at the scent markers over 42 nights, as the current pilots have attempted to do?
The question was asked, why should there have been this astonishingly quick and impressive result?

Was anything else done? Biosecurity? Extra cattle measures? Pre movement testing? No cattle movements at all? Whole herd slaughter? Zones? Licenses? Shrink wrapped grass, raised troughs and cattle in hermetically sealed boxes?

The answer from the minister was unequivocal:

 " The fundamental difference between the Thornbury area and other areas [] where bovine tuberculosis was a problem, was the systematic removal of badgers from the Thornbury area. No other species was similarly removed. No other contemporaneous change was identified that could have accounted for the reduction in TB incidence within the area" [157949] 

More on the Thornbury project, and its effect on TB in cattle in that area can be found on this excellent link (link)

So as all this taxpayer funded 'research' spills into the press, hang on to those basic facts. Everything else is smoke and mirrors. As is the assumed cattle to cattle onwards spread, when said cattle are nailed down on a regime of 60 day test and slaughter.

 A final word from Professor Donnelly, who comments on her latest models thus:

          "These findings confirm that badgers do play a large role in the spread of bovine TB.

These figures should inform the debate, even if they don’t point to a single way forward,”
Perhaps she could 'inform' the BBC of that..... ?

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