Tuesday, August 27, 2013

All clear - in 5 years?

We have been alerted to literature produced by Wildlife Trusts in the English midlands, which tell their members and contributors that if badgers are vaccinated, tuberculosis, the disease which is endemic in them, will cease to be a problem in 5 years. Thus the conclusion is no cull, vaccinate instead.

Sounds easy doesn't it? But is it?

 The Leicestershire and Rutland Wildlife Trust are confident that there will be no bovine TB in badgers after their five year vaccination programme.

 They do mention that vaccination only works in badgers that do not have the disease already.

 But Neil Pilcher, the Senior Conservation Officer at the Trust, says
"..those badgers in the area that are already infected with the virus will die off within the project timescale."
Very comforting. For the pedants amongst us (and of course for Mr. Pilcher ) mycobacterium bovis is a bacterium. The clue is in the full title. It is not a virus. And it would be naive to assume that all or most of uninfected local Leicestershire badgers will be cage trapped and vaccinated annually over the next 5 years, and equally naive to assume that because this product is licensed, it actually works.

As we've said before, the license was issued by the Veterinary Medicines Directorate (VMD) in 2010 on 'elf and safety' data, holds a Limited Marketing Authority (LMA) license only and as VMD so quaintly point out, its efficacy is the 'responsibility of the end user'. 

 Also piling in on the act is the Derbyshire Wildlife Trust, who point out that the pilot culls are "being undertaken as part of measures against the devastating impacts of bovine tuberculosis (TB), a disease which is carried and transmitted by badgers and other wildlife (one water vole??) as well as cattle, and costs the UK cattle farming industry tens of millions of pounds every year".

They also say that:
With the Derbyshire/Staffordshire border identified as another hotspot for bovine TB, a cull could be carried out in Derbyshire in 2014.
After this overview they then regurgitate - incorrectly - the conclusions of the Badger Dispersal Trial RBCT, and thus the Trust condemns culling. Not culling ' as done in this trial', but completely. They point out that an injectible badger vaccine is now available and has been used by Gloucestershire Wildlife Trust.
They continue:
In Derbyshire, we are planning a five-year programme of badger vaccination, starting in 2014. This will contribute to the local control of bovine TB by creating immunity in a population of Derbyshire badgers.

Badger BCG vaccine alone is not the solution to bovine TB, but it does have an immediate effect with no known negative impact other than cost.

Our five-year programme aims to make a worthwhile contribution towards finding a solution to a serious animal disease problem and to explore the practicalities of vaccination. This important work will take a great deal of our time and resources and is currently unfunded.

Please make a contribution to this appeal to help protect Derbyshire’s badgers and fight the scourge of bovine TB.
He's right about badger BCG not being the solution to the problem but no known negative impact? And the cost is £2500 - £4000 per hectare. Or as Wales found out, £662 per badger in one year ?
With already infected wild badgers cage trapped, stressed out, jabbed and released, the jury is out.

So where has this mythical '5 years' to achieve badger immunity come from? Look no further than a Jack and Jill Q & A page on the Defra / AHVLA website. Of course neither of these august bodies are interested in the health of badgers, only in so far as it affects cattle and taxpayer's cash. For this they have a statutory responsibility to test and pay up for tested cattle reactors. A responsibility they seem loathe to shoulder, but let that pass.

The Q & A goes like this:
How long will it take to see a positive effect on the levels of bovine TB in cattle? Mathematical modelling work carried out by researchers at both the Food and Environment Research Agency (FERA, formerly the Central Science Laboratory) and Veterinary Laboratories Agency (VLA) showed that a number of factors will influence the how long it will take for a reduction in disease levels in badgers to translate into an impact on cattle disease.

Whether wild badgers can be caught at all ? We understand there are not many volunteers from genuinely wild populations which are completely different from Woodchester's peanut fed pets.

These include vaccine efficacy, the proportion of badgers vaccinated, what contribution badgers make to the disease in cattle and how effective cattle controls are at preventing cattle to cattle spread.
As we have said, no data was submitted for BCG vaccine efficacy. And all these assumptions for badger BCG rely on mathematically modeled blood tests of those badgers which turned up for a health check.

The contribution to the spread of zoonotic tuberculosis made by badgers is easy. AHVLA risk assessments after new breakdowns, say up to 90% in endemic areas.

And as for the last 40 years of collating information on strains, cattle haven't plastered the countryside with a kaleidoscope of different TB spoligotypes, cattle movements and cattle to cattle spread is overstated by a long mile.
The vaccine is unlikely to benefit already infected badgers, in which case these animals will need to die off naturally for the disease risk to cattle from badgers to be reduced.

Unlikely? It could finish them off, but let that pass.

How long will allowing diseased badgers to 'die off naturally' take and how many victims skin test reactors or pets and companion mammals will die on the way?

Most badgers have a lifespan of just 3 to 5 years and the annual population turnover of the UK badger population is estimated to be 30%, therefore we expect that it will take 5 years to vaccinate a sufficient number of naive badgers to achieve herd immunity and reduce TB incidence within a badger population.
Other work by FERA suggested that an infected badger can live for up to 9 years: an infected sow produces cubs annually over that time and in the confines of the sett, it is likely she will have infected her cubs before they see daylight - or a needle.
And finally from this comforting load of tosh, where all badgers will volunteer for their jabs, the vaccination miraculously works - immediately and no one sees the death throws of a tuberculous badger:
We do not know how long it will take for this to translate in to a reduction in cattle herd breakdowns
Actually, you do. Defra predicted that in some of their paperwork - and it ain't 5 years. A thumbnail of facts about badger BCG can be found here, where Defra quote an estimated time frame for the procedure to affect the population and its upspill into sentinel tested cattle, thus:
"If only 50% of badgers can be trapped and injected with a vaccine which is only 50% effective, and only 50% of farms are involved the disease control benefit becomes rapidly diminished in any given year - 50% of 50% of 50% = 12.5% of the potential available benefit. While there will be a benefit, as any level of vaccination will produce a benefit, it will take substantially longer to appear in terms of reduced cattle breakdowns and vaccination will have to continue for a much longer time in order to accrue the benefit."
That paragraph contains a lot of 'ifs' - as do most of Defra's predictions about badgers and the zoonotic tuberculosis which they carry. But the first 50 per cent (badgers trapped) appears optimistic when applied to a wild population, with single figures being bandied about by some areas.
The 50 per cent efficacy is also a mathematical model, but possibly a good deal more accurate than the mischievous and misleading headline of '74 per cent' which is still doing the rounds.
But bear in mind that BCG does not prevent tuberculosis in any candidate. It may, if it works at all, reduce the size of and spread from lesions. So over generations may damp down disease.

 But Defra have also told us why they are so keen on badger BCG.

This phrase is contained in a 2011 paper on controlling zoonotic tuberculosis:
a): Bovine tuberculosis Animal species: Badger vaccination: Description of the used vaccination, therapeutic or other scheme Badger BCG licensed in March 2010 has been used as part of the Badger Vaccine Deployment Project to build farmer confidence in vaccines as a key tool in an eradication programme.
To build farmer confidence?
What an extraordinary reason for promoting a vaccine which may not work at all, or may not work in an acceptable time scale, for a zoonotic disease which kills.

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