Tuesday, July 10, 2012

Anytime soon would be good...

We read last weeks' news from Northern Ireland with great expectations. With a strapline "Northern Ireland Announces a Badger control Programme", one would expect the thing to be on the starting blocks.
The research project, which will involve a combination of culling and vaccination of badgers, could begin in targeted areas of Northern Ireland as early as next year, the Minister told the Agriculture and Rural Development Committee. She has tasked her officials to develop an approach to bTB control that would involve testing live badgers in the targeted areas. Badgers that test negative for bTB will be vaccinated and released back into the wild, while those that test positive will be ‘removed'.
The majority of farmers we speak to, want this type of approach. Not 'wipe out', not 'extermination' or any other emotive claptrap designed on a Pythagoras based model, but a measured and parallel strategy to protect other mammals from tuberculosis carried by free ranging wildlife. What was interesting was the reported response to this announcement. A measured welcome from Ulster Farming union with the caveat that this approach might take a while, but from the Belfast Telegraph report:
The Northern Ireland Badger Group also said it welcomed the minister’s announcement of a science-led badger strategy.
Well ain't that a surprise? After decades of blaming cattle and their owners for the spread of tuberculosis among many other mammals (and human beings), they 'welcome a science led badger strategy'. Mmmm.
So we asked exactly what 'screeening tests' would be used to identify groups of infected badgers. Together with others who enquired, we received what can only be described as a 'fudge' :
“Considerable preparatory work is required before the TVR approach can be finalised. The first step will be to commission the necessary mathematical modelling in order to help us design this wildlife intervention research to ensure that it is scientifically robust. This modelling will help us to answer “what if” questions, identify the most appropriate area, the optimum size of that area, and the appropriate duration of the intervention.
Methods of badger capture and removal and the types of tests to be used are also under consideration as part of this preparatory work. Animal welfare considerations will be paramount in the test, vaccinate, remove (TVR) approach that we are planning to pursue in the north of Ireland. We are committed to ensuring that any badger removal will be undertaken in as humane a manner as possible and in compliance with the terms and conditions of any legal requirements.”
So what is on the table to 'model' as a screening test for TB ridden badgers? This has been trialled before. First a lab based blood assay, known as the 'Brock Test' about which the ISG in their Final Report had this to say:
1.7 [] ... A live test for badgers had been developed and subject to trial from 1994-96, but its sensitivity was much poorer than had been hoped, successfully detecting only about 40% of infected badgers (Clifton-Hadley et al., 1995-a,Woodroffe et al., 1999)
Then Chambers et al, they of the '74 per cent' fame at FERA had the following comments having investigated the Stat-Pak blood screen :
The Brock TB Stat-Pak is a lateral flow assay to test for the presence of antibodies in serum to M. bovis antigen MPB83. It has an estimated sensitivity of 49.2% and an estimated specificity of 93.1% based on a study of 1464 badgers naturally infected with M. bovis as determined by culture (Chambers et al., 2008). Sensitivity of the Stat-Pak varies according to disease severity, such that sensitivity was found to be 34.4% in infected badgers with no visible lesions at post mortem, 66.1% in infected badgers with visible lesions at post mortem, 41.7% in infected badgers that excrete M. bovis; rising to 78.1% in so-called "Super-Excretor‟ badgers (Chambers et al., 2008).
So, to date, with much fanfare publicity, not born out by the results of 40% and 49% sensitivity respectively, two laboratory based blood tests, which require animal capture and blood samples before action - in either direction. Compare this, to the total media silence on this screening test, which can be field based, uses faecal samples, is pretty much instant and whose candidates may either vaccinated or 'removed' on results of over 80 per cent sensitivity - and no false positives. PCR is now a peer reviewed and validated test for TB in badgers, and awaits a larger field trial. Where? Ireland? Wales? England? Don't all shout at once.

We wait with baited breath, the results of the 'modelling' described in our reply to 'how are you going to do this'. Of course, being simple souls, we could suggest using the sentinel tested cattle as 'canaries' of a wildlife problem. But that wouldn't involve a 'scientist' or a model. We are assured that no coughing badger will be harmed in this exercise, but don't expect anything to happen any time soon. They still have to work out the 'removal' bit.

(With acknowledgement and thanks to Ken Wignall for the use of his cartoon, first published in Farmers Guardian)

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