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Badgers and bTB - a bit more info.


Kes
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I have been maintaining an interest in bTB and badger linkages - trying to get a true perspective and explain the results of recent culls and also to be better informed.

This scientific article extract is perhaps the beginning of a technique to answer the question fully in the short to medium term -

 

"Whole genome sequencing (WGS) technology holds great promise as a tool for the forensic epidemiology of bacterial pathogens. It is likely to be particularly useful for studying the transmission dynamics of an observed epidemic involving a largely unsampled reservoir host, as for bovine tuberculosis (bTB) in British and Irish cattle and badgers. BTB is caused by Mycobacterium bovis, a member of the M. tuberculosis complex that also includes the aetiological agent for human TB. In this study, we identified a spatio-temporally linked group of 26 cattle and 4 badgers infected with the same Variable Number Tandem Repeat (VNTR) type of M. bovis. Single-nucleotide polymorphisms (SNPs) between sequences identified differences that were consistent with bacterial lineages being persistent on or near farms for several years, despite multiple clear whole herd tests in the interim. Comparing WGS data to mathematical models showed good correlations between genetic divergence and spatial distance, but poor correspondence to the network of cattle movements or within-herd contacts. Badger isolates showed between zero and four SNP differences from the nearest cattle isolate, providing evidence for recent transmissions between the two hosts. This is the first direct genetic evidence of M. bovis persistence on farms over multiple outbreaks with a continued, ongoing interaction with local badgers."

 

It has also been stated that culling has eliminated some badgers and would perhaps have reduced bTB transmissions but for the "peturbation effect". This effect results from elimination of 'healthy badgers' by culling and the establishment of bTB carriers in their former territories. This latter effect can, apparently, in areas where culling is poor and bTB infection high, result is no detectable difference in bTB cattle infection rates or, in certain cases, an increase in bTB transmission and numbers of reactors. Everything I have read which is not emotionally-based conservation pleading, is in favour of culling for bTB but also environmental diversity. The arguments about environmental diversity, and the control of certain predators, carrion crows, magpies, hooded crow, badger, fox, buzzards etc will strengthen (if allowed to) and, I believe have the potential to justify future controls to maintain biodiversity. The question would appear to be - how to fund the new forms of Whole genome sequencing to disease transmission and control in widlife/economics. Its already providing answers in human transmission.

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I just see the whole BTB excuse as strange really saying its not badgers.

 

If someone could explain to me then, as a few may remember around the 1960 or a tad before we had a large problem with TB in the UK. they sorted that out, Back then they were controlled and you hardly ever heard of anyone contracting TB humans or cattle for decades after. So whats changed so much nowadays that we have out brakes of TB in the UK on quite a regular occurrence.

 

I obviously have my suspicions, and my own opinions of course.

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I just see the whole BTB excuse as strange really saying its not badgers.

 

If someone could explain to me then, as a few may remember around the 1960 or a tad before we had a large problem with TB in the UK. they sorted that out, Back then they were controlled and you hardly ever heard of anyone contracting TB humans or cattle for decades after. So whats changed so much nowadays that we have out brakes of TB in the UK on quite a regular occurrence.

 

I obviously have my suspicions, and my own opinions of course.

There is also an interesting article on the very subject of bTB in the 60's and 70's. Apparently Cheshire was a TB hotspot and now is a 'fringe' area.

Its not hard to conclude that culling eliminated the disease from Cheshire, where dairy is the main agricultural industry. Farmers here still feel that they should be allowed to cull to eradicate the disease again.

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If someone could explain to me then, as a few may remember around the 1960 or a tad before we had a large problem with TB in the UK. they sorted that out, Back then they were controlled and you hardly ever heard of anyone contracting TB humans or cattle for decades after. So whats changed so much nowadays that we have out brakes of TB in the UK on quite a regular occurrence.

It's mainly due to a number of factors:

  • Less badgers about
  • Less livestock movements
  • Lower herd sizes

When you have greater numbers of cattle on a farm the disease spreads to more animals. Farmers buy and sell stock from all over the country (and abroad).

 

Badgers are involved in the local transmission of the disease and they will cross borders and take the infection to neighbouring farms. Cattle movements bring TB into new areas. If you only shoot a few badgers their social group is broken up and they will wander to find others - this is the perturbation effect. The solution is as close to 100% kill as possible in a good sized area.

 

I don't know if any of you saw the paper published, that found hedgehog numbers double once you kill some badgers:

 

http://www.ncbi.nlm.nih.gov/pubmed/24736454

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Interesting addition to the debate confirming countryside observations. We have no hedgehogs but loads of meles meles. I agree that eradication is the only way to cull badgers to prevent bTB but, is there a way only those with bTb can be identified and cullled? ? That way the disease cannot get back into the cattle but if transmission is both ways then a negative bTB test would need to be a precursor to any cattle movement ?

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