For a short time only, Defra have posted the Tb statistics for January - November 2006.
http://www.defra.gov.uk/animalh/tb/stats/latest.htm
Defra describe the results thus:
"There has been a provisional 7% reduction in the number of new bTB incidents in Great Britain in January to November 2006 compared to the same period in 2005. There was a considerable drop in the number of new incidents in the first four months of 2006 compared to 2005. However, since May the number of new TB incidents reported in 2006 was slightly up on 2005. As a result, the percentage decrease in new incidents reported in previous months has now reduced" .
From March, when the drop in New Herd breakdowns was almost 30 percent, the fall (and thus increase) in bTb incidence has reduced and now stands at 7.2 per cent lower than in 2005 at the same time.
We have tracked these results with a great deal of scepticism, and reported our thoughts regularly. The immediate candidate for the fall was the substitution from September 2005 of our own UK produced 'Weybridge' tuberculin antigen with a product made by Lelystatd in Holland, which although a similar product, was found in the CVO's report to have given "a small but statistically significant difference" in performance. Annex C of the same report described the difference thus:
"The sensitivety of the combined dutch PPD is less because of failing to pick up NVLs ( animals which could be in the early stage of disease)... [ ] This would result in underdetection of cases, resulting in a transient decline in cases reported, despite there being no true decline in cases."
We covered this at http://bovinetb.blogspot.com/2006/08/going-dutch-2mm-difference.html
At the time of the CVO's report, the authors, despite blaming their veterinary practitioners for jabbing the cattle in the wrong way (Have they all been retrained? All of them? Really? Wow..) leant towards this explanantion, but is it the whole story? For figures to be comparable, the root raw data must be from the same source, and in this case it is not.
Data in the past has been drawn solely from routine tuberculin skin tests. For sure, as bTb increased, so did the skin tests as more and more parishes fell under annual regimes.
And over the last two years, Defra has come down hard on the cattle side of bTb - short of the obvious of course, and that means testing annually every herd in the country, but let that pass.
Parish testing intervals have been extended outwards, drawing more farms into more regular testing, but also farmers' own pre movement testing results will build into these figures, giving a further increase in herds and cattle tested which was not in the data from 2005 or prior to that. Defra are compunding this increase with a 'hypothetical drop' of around 23 percent in bTb, given the increase in testing. Into this mish mash of figures add gamma interferon, now in use in all areas but under different circumstances, and the picture is even more muddled.
It is our understanding that in areas of annual and two year testing, a third time IR skin tested would only result in around 15 percent failure rate. But those animals now get no third chance; after two Inconclusive tests, gamma interferon is routinely used. And it is giving a failure rate of 50 percent. For what reason we can only repeat previous info. That this diagnostic test is different, picking up antibodies to bTb in the animal's blood and that it is much less 'specific' than the comparative skin test. We understand that it is confusing, amongst other things paratuberculosis (Johnes disease) which may or may not be a good thing - but when lumped together in a bTb statistical context, is misleading. Many will argue, probably quite rightly, that in a hot spot situation, many cattle will have had a small exposure to m bovis, and thus need a higher exposure to provoke either the disease itself, or a skin reaction to it. But Gamma interferon will take out exactly those animals who have acquired this degree of immunity. For more see: http://bovinetb.blogspot.com/2006/11/new-leaflet-farmers-would-prefer-not.html
And then there is the weather. Blazing hot sunshine - with associated ultra violet - is the single most lethal influence on m.bovis. And we've had two consecutive summers, where its survival on grassland has been severly curtailed- to the benefit of any grazing cattle who may encounter it. The downside of the heat and the hard packed ground, is hungry badgers, foraging this summer, we hear, in farm buildings. The results of which will only show up in cattle tests this winter and into the spring.
But we are aware that with all these different data streams into the statistics, it is very difficult to compare. So we will concentrate on the figure which draws the attention of our trading partners. Bearing in mind that to achieve OIE 'Tb free' trading status, the number of herds under Tb restriction in a given period must be less than 0.02 per cent of herds registered on the country's database, the only thing we see, is that headline figure of GB herds under bTb restriction as a percentage of herds registered on Vetnet, is UP.
To November this appalling figure stands at 6.10 percent. An increase of 0.2 on last year.
6 comments:
From Trevor Lawson, Badger Trust
As always, you conveniently leave out half the story. Compared to 2005, the number of herd tests in 2006 was up by 17 per cent and the number of cattle tested was up by 13 per cent.
Last year, Mitchell et al (Proceedings of the Society of Veterinary Epidemiology, Exeter 2006) reported that 83 per cent of cattle were never tested for bovine TB and that as a result the TB testing regime was missing infection. It's no surprise then, that more testing is finding more infected herds. You suggest that this must be due to badgers. This is disingenuous at best.
It is disappointing to see your vague challenge to the benefits of gamma interferon. The Government's TB Advisory Panel (which includes three individuals who have previously advocated badger culling) this week added its support for gamma interferon precisely because it detects bovine TB earlier and means that vets need only visit a farm once, thus reducing overall inconvenience.
You appear to suggest that gamma interferon culls immune animals. The very nature of the TB testing regime means that this must inevitably, on very rare occasions, be true. But are you seriously suggesting that gamma interferon is not removing cattle in the early stages of infection?
In the past, you have criticised me for not providing references (although everything the Badger Trust says is references in papers on its web site). Where are your references to support your gamma interferon hypothesis?
Best wishes,
Trevor Lawson
Badger Trust
Well Trevor, we thought we'd covered most of the 'story' - but obviously you missed our point.
You say "the number of herd tests up 17 per cent and cattle tested by 13 per cent".
We said: " .. as bTb increased, so did the skin tests as more and more parishes fell under annual testing regimes"
and "...Parish testing intervals have been extended outwards, drawing more farms into more regular testing, but also farmers' own pre movement testing results will build into these figures, giving a further increase in herds and cattle tested which was not in the data from 2005 or prior to that."
What part of that didn't cover more herds and more cattle tested?
Furthermore we went some way to explain why.
You quote "the Society of Veterinary Epidemiology, Exeter 2006) reported that 83 per cent of cattle were never tested for bovine TB and that as a result the TB testing regime was missing infection."
Havng endured several years of 60 day consecutive tests and with three contributers to the site under bTb restriction again, we find this a little hard to swallow. But we're realistic and did point out in our post that .. "over the last two years, Defra has come down hard on the cattle side of bTb - short of the obvious of course, and that means testing annually every herd in the country, but let that pass."
Sorry you missed that bit too.
Now ... "disingenuous" you say, to involve your little furry friends. No Trevor. We have asked you many times to hypothesise the source of our bTb outbreaks, as NO BOUGHT IN CATTLE were involved - or even on the database at BCMS - if badgers were to be excluded. That's the emaciated, sick, and dying badgers which were picked up on our farms, on the surrounding roads and in our buildings by the way, not the shiny, bushy tailed individuals which decorate the collecting boxes of the Wildlife Trusts and your good selves.
No cattle 'ON' movements Trevor. Not one, let alone 14 million - yes that little gem is still doing the rounds. But so far - silence.
Well there would be wouldn't there?
In areas of 3 / 4 year testing, we have no problem with gamma interferon; except the obvious of course - that in the absence of a wildlife reservoir of disease, it is unecessary and if, like the UK, a country has such a pit of infection, then it is a waste of time and resources. There is a case for it in Australia, as the bTb strains out there can take up to 7 years to appear, while ours flag up an immune response to the skin test in under 221 days.
The sensitivety of GI was explored in PQs;
8th Dec 2003; Col. 218W [141969] and pusuant to that, 23rd, March 2004 :Column 697 W [158363]
The Minister said :"The test is more sensitive than the SICC, but less specific meaning it results in a higher probability of false positives"
He upheld our figure of 60 - 65 per cent specificity, dodging - as he frequently does - the rest of the question.
We feel it speaks volumes that in areas of the country where a wildlife vector is a known and acknowledged source of infection to herds like ours, GI is not offered except as a mop on third time IR's, where SVS sources indicate a failure rate of 50 per cent compared with the intradermal skin test's rate of around 15 per cent. Our point then and now is that all these variables will affect the raw data used in Defra's monthly statistics.
So ... not 'vague' at all. Parliamentary questions, posed with the express intention of drawing out information, and experience of vets using the test in the field.
We hear that GI is not too successful on entire bulls over three years old either, giving varying degrees of accuracy - or not. But that is one contributer's personal experience - and not scientific at all. (The bull was an IR at skin test, passed a GI test, but was found at the slaughterhouse to have lesions.)
You offer your good wishes. We will pass those on to the 1400 cattle which will undergo a bTb test in our respective herds this week. Russian roulette, or a reprieve? We'll let you know.
It is not worth arguing with Trevor Lawson and his Badger Cult - they are no different from creationists. If they weren't involved in the Badger Cult they would probably be busy arguing about how the dinosaurs couldn't get on the Ark because they were too big for the doorway, or how far we have to sail before we fall off the edge of the earth.
I had my TB test on Monday, thats it over for another four years! In those four years I will put away about 350 head of clean cattle for beef and a few who have a calve but fail to stay in the dairy herd for any length of time.
It is only the breeding stock that are tested for TB in those areas fortunate enough not to have a TB problem and therefore it is quite easy to see how Trevor Lawson's figure of 83% of cattle never being tested is reached.As usual he is clutching at straws.
We lost two more cows today.One was due to calve in two weeks time. That makes over 60 slaughtered in two years. I am still waiting for Mr.Lawson to tell me how TB entered our closed herd (and come to that all the other closed herds that have been affected). It certainly was not cattle movements. Come on Mr.Lawson, don't be shy, just take a deep breath and give it a try.You have got to come out at some time and give us a reasonable explanation for our predicament.
P.S.Thanks to all who run this blog for your hardwork in very trying times.
To our last three 'Anonymous' commentators - thanks and welcome.
Yup - we christened Mr.Lawson's predecessor (Dr. Elaine King) high priestess of the 'Flat Earth Society'. Having obtained a useful addition to her CV in the shape of a doctorate whose title was "Factors influencing the risk to cattle of infection with
bovine tuberculosis (Mycobacterium bovis) from badgers (meles meles)", the lady then procedded to find gainful employment by denying any such risk.
Interestingly enough none of us have been able to view the work, which we understand lurks at Bristol University - allegedly - and which under the terms of the doctorate awarded, should be available for public view.
Anon 2. Both Matt 5 and Matt 1 used to be in such areas, (Midlands) which had a test of all breeding stock over two years old every 3 years. Routine really, but not any more. Our old stomping grounds are now caught up in the ghastly 60 day testing racket. Whether it was Tb takeaways (translocated badgers) which caused the problem, or an infected cow is now immaterial now. The fact remains that of all the AHO (Animal Health Offices) in England and Wales, not a single one had '0' herds under restriction in the reporting period to November 2006. Only the Scottish Inverness office had that honour. And the areas which saw initial cases a few years ago, are not clearing them. They are 'amplifying' (Defra speak for getting worse, I'm told) - well they will if nobody is prepared to take out the cause.
To Anon 3, you have our sympathy. Been there, done that. Shot the cows, lost the calves they were carrying too. BCMS were very helpful, and confirmed in writing that on their database we had 'No Bought in Cattle', or for Matt 1., 'none in the last 6 years'. Not that that makes too much difference if such purchases are post movement tested. If the infection is in the wildlife, anything you may do short of clearing that out, is sticking plaster. It gets you in the end - and it moves at the rate of about 6 miles / year to the next farm ... and the next .... and ..... keeps Mr. Lawson and the bTb magic circle in handbags?
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