The 'Early detection' potential of gammaIFN

Following our postings below on Defra's newly discovered love affair with gammaIFN, and its subsequent carnage , the twitterings spirited defence of the test from London continues to concentrate on its ability to facilitate 'early detection' of Tb. In written parliamentary questions - the answering incorrectly of which is a hanging offence - an epidemiological roadmap of bTb has emerged, which has proved most useful.

Dec 2003: Column 218W

Mr. Paterson: To ask the Secretary of State for Environment, Food and Rural Affairs what plans she has to replace the TB skin test used on cattle as a preliminary diagnostic aid with a more accurate and sensitive test. [141969]

Mr. Bradshaw: Improved diagnosis of TB in cattle is a major objective of Defra's wide-ranging research programme. The current most promising candidate is the gamma interferon test, a laboratory-based blood test that measures the immune response to M. bovis (the causative agent for bovine TB) of T-cells in cattle blood.

This test was officially recognised by the EU in July 2002, but only for use as a supplement to the Single Intradermal Comparative Cervical Test (SICCT) in TB affected herds. The test is considered more sensitive than the SICCT, but less specific, meaning that it results in a higher probability of false positives. For this reason, the gamma interferon test cannot be used on its own as a screening test for TB for the time being.

So, a supplementary test with a higher probability of delivering false positives, but are Defra correct in informing their ministers and the public that gammaIFN will detect Tb at an 'earlier stage'. No. From answers to written parliamentary questions, they are not.

23rd March 2004: Column 689W
Mr. Paterson: To ask the Secretary of State for Environment, Food and Rural Affairs how long after exposure to an infective dose of M.Bovis bacilli a bovine animal becomes infectious, and what the typical duration of infectivity is [159074]

Mr. Bradshaw: Published figures for the time from exposure to being infectious include 87 - 226 days after natural exposure in a United Kingdom study.[ ] The typical duration of infectivity is not known.

Now we are sure you don't need reminding that Tony Yewdall's cattle waited in limbo for at least six months before slaughter, as did those of the Somerset based Burrough Farm Partnership. And we have discussed before the latency of the skin test as being a published 30 - 50days from exposure to flagging up an immune response to a bovine tuberculin antigen jab. (Gamma has a latency of approx 28 days) The maximum exposure window for these cattle, could have been that length of time before the previous skin test which may have been at 60 days, six months, a year or several years, depending on herd and parish disease status.

Only 7 of 177 cattle slaughtered after gamma bloods had visible signs of Tb. And those were not necessarily at an infectious stage. How long had they been waiting? The thick end of eight months - or 240 days from the latest possible exposure. And how long did PQs tell us was the maximum time of an animal becoming infectious after natural exposure? Yup, you read it correctly. A range " 87 - 226 days ".

So we repeat - as does our big sister site, what an appalling, absolutely avoidable waste.

Bring on the clowns...

Periodically, Defra produce a Departmental Report which sets out PSAs (Public Service Agreements) which are then presented to parliament.
The 2008 report gives an overview of Defra's activities 2007-08 and looks ahead to what they hope to achieve in 2008-09.

The report highlights Defra's target for bTb thus:

A reduction in the spread of Bovine tuberculous (TB) to new parishes to below the incremental trend of 17.5 confirmed new incidents per annum by the end of 2008.

A singularly modest aim, in which they award an overall self assessment described as 'On Course'. But while a great deal of back slapping and self congratulation may take place in the corridors of Noble House, or wherever they hang their hats presently, out here in the sticks things are far from rosy.

On a different part of Defra's labyrinthine website are the figures for Tb reactors tabulated over nine years. And they certainly do not give the impression of being 'on course' for anything at all except total annhilation of the UK cattle industry. Official figures show a staggering increase in cattle slaughtered, especially in new areas.

In 1998 GB recorded 6191 animals culled as reactors, IRs or DCs. But in 2007 that figure had increased to 28,200 - and increase of 355 per cent.

The West region suffered worst losses, with 4339 cattle slaughtered in the year after the moratorium of badger culling, while the 2007 figure had jumped to 16,492. But despite Defra's warm assurances, areas not particularly affected by TB in 1997 showed much bigger increases, with Wales jumping from 1046 cattle slaughtered nine years ago to 7913 last year. And in the Eastern region of the UK, from just 81 cattle slaughtered in 1997, a staggering 1162 per cent increase took that figure to 1022 last year.

And the TB figures for March are not in any way 'on course' for a decrease with GB recording an extra 579 herds under restriction due to a 'Tb incident' in the first three months of the year. Cattle slaughtered jumped by 24.5 per cent, from 7816 to 9732 and that on less herds and less cattle tested.

So 'On Course' we feel is a comfort blanket too many. For sure 1400 staff have had the push, so that's saved on wage bills, but with a disease increase of the magnitude we have outlined and its associated costs, 'on course' depends aspirations, expectations and on high one puts the bar.

And from where we sit, that is barely off the ground.

More comment on this story fromFarmers Guardian

Carnage

... or death by one thousand cuts. Today, over 80 of Tony Yewdall's newly calved pedigree guernsey cattle were slaughtered. We covered the story of this farm's Tb problems here in 2004, but last November two further reactors were identified by the skin test. Defra moved in to blood test the cattle. Why, when the herd had ongoing Tb problems, a history of Johnnes disease and hundreds of badgers, is for them to comment on. Not the brightest idea, one would have thought. The result was a far cry from a couple of reactors identified by the primary skin test. A devastating 89 cattle failed the blood test.

This led to the appeal in the High Court last month, on behalf of several farmers including Mr. Yewdall, who requested a judicial review into the use of this test. Meanwhile the cattle have been in isolation and on regular Defra watch pending the outcome which we covered in this posting.

The farcical failure of this appeal for Common law over disputed statute, is one of life's mysteries. And today, Tony Yewdall's cattlepaid the price.

South west newspaper, Western Morning News carried the story:

Today, the Yewdalls are debating whether to remain in the business amid the double blow of losing a third of their valuable dairy herd and the fear many of them may be perfectly healthy. Mr Yewdall, who successfully resisted having his herd culled during the foot and mouth crisis, said today's blow could be the last straw. "It's a difficult decision, but getting out of farming is certainly an option," he said. "We will have to see what happens with TB in the future. The really hard thing is that we question how many of these animals actually have TB, and that won't be answered until tests are carried out once they are dead.It's a dreadful situation for us."

His son, Jonnie Yewdall, estimated the episode would cost the family about £100,000 -particularly as Defra is paying the [tabular] compensation value for each cow based on November's prices, which were lower than today's.

He said the family had offered to pay for a retest privately, but Defra had refused to grant the necessary authority to do so. "Why would they refuse if they are confident in their results?" he asked.

"Nobody's doing anything to stop badgers spreading TB to cattle. If we carry on in farming, it's as if we're sentencing our cows to a premature death. It's like banging your head against a wall."

A Defra spokeswoman defended the differences between the skin test and the blood test, known as the gamma interferon test. She said:

"Research shows the two tests identify different populations of infected cattle. The gamma interferon test can identify infected animals at an earlier stage in the disease as well as infected cattle that simply fail to react to the skin test. In herds with confirmed infection, the use of both tests in parallel offers the best prospect of detecting all infected at the earliest opportunity."

Well she would say that wouldn't she? Sheesh - that 'earliest opportunity' is just 12 days. The difference between the latency of the skin test (picking up exposure to m.bovis) at 30 - 50 days post exposure, and gamma at 28 days average. Of course it also, as that shambles of a Pilot study found, picks up a whole shed load of other contaminants and relabels them 'm.bovis'.

And joining in the clamour to use this bluntest of blunt instruments, is none other than our old friend, Trevor. Yup, Mr. Lawson loves it, arguing that gamma interferon

"... provides a very rapid and very reliable test for bovine
TB.It only requires one visit from the vet and the results can be ready in 48 hours. Furthermore, the cut-off point for the test can be adjusted, so that a 'false positive' diagnosis can be virtually eliminated. Although this does mean that some infected animals could be missed, it is still far better than the skin test, which misses around one third of infected cattle. If a positive diagnosis were in doubt, it could then be verified by a more specific gamma interferon test to minimise the risk of slaughtering a healthy animal."

Although we are delighted that our Trevor has concerns about slaughtering healthy cattle, his spin interpretation of the test sounds to good to be true. And of course it is. We are not sure which planet - or should that be sett? - Trevor Lawson inhabits but not the same one as the rest of us. Flexibility? Not on this watch. And not at all in Tony Yewdall's case. Cut-off point adjusted? Nope. It's set at 0.1 and not adjusted for farm circumstance, contaminant circumstance or any other goddamn circumstance. False positives virtually eliminated? Well, we'll see. Skin test reactors show about half +/- 50 percent to have confirmed disease, compared with 18.6 percent 'reactors' to gamma. As Mr. Yewdall said, only postmortems will tell the whole story. These cattle failed the blood test in November. Six months ago. They were slaughtered today. And if Defra are right, every last one should have developed full blown disease, defined by Visible Lesions or cultured samples. And of course that will be the end of Mr. Yewdall's Tb problems won't it? The blood test having hoovered up all the cattle the skin test failed to find? Not necessarily. In fact highly unlikely. And that 'thirty percent of cattle' that the skin allegedly misses ? Selective spin. For goodness sake man. Get a grip. Or better still read this

But we are not alone in wishing that a blood test would sort the problem out - the problem of 50 per cent of skin test reactors proving negative to tuberculosis on postmortem would be a good start. (94 per cent of ours) But it won't. In fact the rigid cut off may actually target cattle which have acquired a degree of resistance to TB infection, so it could actually be counter-productive. There will still be infected animals on Tony Yewdall's farm - but they won't be the cattle...

An MRCVS veterinary surgeon described his experience of the gamma test thus;

All my clients who were ‘conned’ into having the blood test - one twice -lost many times (10/20? times) more cattle than would have been expected and therefore necessary. All of them still have a TB problem in their herds. None would “go down that route again”.
One client with a long standing, ongoing problem, had had tuberculin tests virtually every 60 days for the previous 4 years. A tuberculin test with 2 reactors, was followed 21 days later with a blood test with 23 more ‘reactors’. 41 days later, I found 27 more reactors of which 13 had lesions. There was a lot of badger activity.

Until the infected badgers are culled there is no place for the blood test. When they have been culled there will be no need for the blood test!

We will add more links from other publications on this story, as we get them.

UPDATE
The postmortem results on Mr. Yewdall's cattle are now to hand. After 6 months in isolation, just 2 cattle had Visible Lesions and a further 3 were found to have the very beginnings of small closed granulomas. Over 80 cattle were slaughtered in this carnage - as 'reactors' to the secondary, ancillary gamma interferon blood test. They had survived under an injunction for the best part of eight months in which the opportunity was there to produce full blown disease and prove Defra's point.

What a splendid result for our beloved Defra.
What a total waste of £200,000 for the UK taxpayer.
What a devastating and irreplaceable waste for the Yewdall family.

And a similar result has come from the Burrow Farm Organic Partnership, whose case for a Judicial Review of the secondary, ancillary blood test after some more spectacular results failed last month.

88 cattle went for slaughter this week. Just two had visible lesions consistent with confirmed tuberculosis. These cattle, as with the Yewdall's herd, had been in isolation for several months, pending the court decision. Defra's defence of this brutal of blunt instruments as 'flagging up early detection' of Tb, is looking decidedly thin.
See also comment below from a farmer who kept a gamma postive cow for twelve months, arguing for a skin retest. The animal was negative on both VL and culture but at postmortem was found to have harmless epidermal granulomas known as 'skin tb'.

We did entitle this posting 'carnage'....

More on this story from Christopher Booker's Notebook
in the Sunday Telegraph.

Top of the pile

Farmers Guardian this week carries an exclusive report into a prize winning dairy herd near Cardigan in SW Wales. In last year's National Milk Records competitions for Pembrokeshire, the Vaughan family's 'Cilast' herd swept the board, winning five classes, including the overall large herds section, and being placed second or third in eight others, based both on inspection and production criteria.
But the Vaughan family are now among the top contenders for another title – one that no-one wants to hold. Since a bTb breakdown in 2001, a total of 521 of their prize winning cattle have been slaughtered, with 366 going since last August - when the cattle were judged for the NMR competitions.

The farms lie near the Pembrokeshire border with Carmarthenshire, which is at the heart of Wales' 'hot-spot' areas, and after this latest devastating clearout, the sheer numbers of cattle affected probably ranks the herd as one of, if not the worst, of Britain's cattle herds devastated by bTb, which of course remains unchecked in its maintenance reservoir.


Farming as Cilast, the family’s 550-acre, two-farm dairying operation based at Boncath, not far from where Pembrokeshire borders on both Ceredigion and Carmarthenshire, lies at the heart of one of the country’s top ‘hotspot’ areas for the disease.

The Vaughans have no doubt either that infected wildlife is the most likely cause of their prolonged misery. Evidence of badger activity has been seen on the land and the farm has 50 acres of woodland.

Such reasoning is backed, too, by the fact that ever since Mr and Mrs Vaughan first began keeping pedigree black and whites 40 years ago – based on Hunday breeding – the emphasis has been on maintaining a closed herd. That was certainly the case in the run-up to the first case of TB being diagnosed back in 2001, when four animals were taken out.

After that initial breakdown, in a herd with no bought in cattle, the relentless round of 60 day testing clanked into action. And doing exactly what it says on the tin, the skin test picked up a further 15 animals with exposure to Tb. In 2003, 35 were lost and 15 in 2004. It was then that the number of cases started to explode.

In 2005 the figure jumped to 44 and in 2006 a further 26 failed the testing. Last year eight went in February, another eight in May, 74 in August, and 65 in October – before hitting three figures in December when 106 cattle went for slaughter. Another 106 failed in January this year, 10 in February and five in March.
Of the 366 slaughtered since last August, 250 have been milkers – 47 classified as Excellent, 103 VG and 36 VG two-year olds.

By any standards these were superb cattle. And after six years exposure to an increasing burden of Tb infection in the wildlife sharing their habitat, they are dead. Three quarters of this long established and home bred herd have gone - on the altar of prevarication and political expediency. Farmers Guardian continues:

The consequence is that the heart has been ripped out of a herd proud of its pedigree status and riding high as a result of the selective breeding that has gone into moulding such a high-flying herd with an average yield consistently topping the 9,700 litre mark. Such decimation means that two-thirds of the unit’s fully-modernised cubicle housing is now lying empty, more than £300,000 has been lost in milk sales in the past six months alone and there is no longer enough work for an employee.

Having been in the same position - but on a smaller scale - as the Vaughan family, we understand their feelings and utter frustration. Barry Alston's full report and pictures can be read here