Sunday, January 29, 2017

In the UK, we shoot the canaries, don't we?

We frequently refer to our regularly tested cattle, as 'canaries in the coalmine'. These tiny birds were taken into coal mines as an early warning system. Toxic gases such as carbon monoxide, methane or carbon dioxide in the mine would kill the bird before affecting the miners. Signs of distress from the bird indicated to the miners that conditions were unsafe due to the presence of gas.
So, if the canaries fell off their perches, it was time for the miners to leave. Quickly.

If cattle react to the skin test, they are sending a message that the bacteria which causes zoonotic Tuberculosis is around in the environment and available, not only to tested sentinel cattle, but any mammal..

From the NZ Farmer comes a much more sensible way of reacting to these 'biological markers' - [link] for a disease which may affect cattle or deer in a country which is heading for TB Free status in the very near future. In an area of New Zealand thought to be clear of TB, the disease has been found in wild pigs.
A survey of Marlborough's wild pig population is helping determine the extent of bovine TB in the region. Pig hunters have been contracted by OSPRI and Landcare Research to hunt in specific areas and collect pig heads for TB analysis since July. Lymph nodes under the neck of the animal can show that TB was evident in the region. Pigs contract TB by scavenging dead animal carcasses which have been infected, but do not pass on the disease themselves.
In New Zealand, the wildlife vector of zTB  is the brush tailed possum, so by checking wild pigs for disease, the authorities conclude:
"When TB is present in possums in an area, it is highly likely that it will also be present in local pigs. If we can pinpoint where disease is, we can be specific about possum control."
And the New Zealand authorities do 'control' those possums. Whereas in the UK, we test the canaries ( cattle) and then shoot the messenger. Leaving the wildlife vector to run wild and free. Farm to farm.

Very sensible.

Saturday, January 21, 2017

If it's good enough for the Aussies??

A new and said to be 'highly reliable' diagnostic solution - [link] for bovine tuberculosis, a major infectious disease among cattle, other farm animals and certain wildlife populations, is now on the market, reports Vet Practice magazine (Australia)
“The VetMAX M. tuberculosis Complex PCR Kit is a reliable and fast tool to confirm the presence of mycobacteria belonging to the tuberculosis complex,” said Martin Guillet, global head and general manager of AgriBusiness at Thermo Fisher Scientific, the company that has developed what is the only commercially available PCR test that detects all seven strains of the M. tuberculosis complex in a single solution.
Using the test on suspect cattle lesions, the article explains that results using this PCR approach can be returned much faster when compared to bacterial culture testing methods. While the results of a M. bovis culture can take up to six weeks, results using PCR—from sample preparation to testing—take just three hours.

 And we note that the same kit (VetMax M. tuberculosis Complex PCR) was trialed in 2014 alongside conventional culture testing on abattoir suspect lesions, in France - [link] This is the result:
The aim of this study was to estimate and compare sensitivities and specificities of bacteriology, histopathology and PCR under French field conditions, in the absence of a gold standard using latent class analysis.

The studied population consisted of 5,211 animals from which samples were subjected to bacteriology and PCR (LSI VetMAX™ Mycobacterium tuberculosis Complex PCR Kit, Life Technologies) as their herd of origin was either suspected or confirmed infected with bTB or because bTB-like lesions were detected during slaughterhouse inspection.

Samples from 697 of these animals (all with bTB-like lesions) were subjected to histopathology. Bayesian models were developed, allowing for dependence between bacteriology and PCR, while assuming independence from histopathology.

The sensitivity of PCR was higher than that of bacteriology (on average 87.7% [82.5–92.3%] versus 78.1% [72.9–82.8%]) while specificity of both tests was very good (on average 97.0% for PCR [94.3–99.0%] and 99.1% for bacteriology [97.1–100.0%]). Histopathology was at least as sensitive as PCR (on average 93.6% [89.9–96.9%]) but less specific than the two other tests (on average 83.3% [78.7–87.6%]).

These results suggest that PCR has the potential to replace bacteriology to confirm bTB in samples submitted from suspect cattle.
As regular readers will have guessed, we are fans of PCR diagnostics - [link] both for speeding up diagnosis in cattle lesions, and having pushed government to support its use, identifying infection in badgers.

So were somewhat floored by the reaction of its British developers - link] (scroll forward on the video to 20 minutes in to see that reaction which we have pasted below.)
" I’m extremely busy and it’s difficult to find time to watch the film as it is long, however, I have just watched it and I don’t feel I can be involved in the film as the tone and message are not in line with my views. Some of what has been said is unscientific, including some of the comments from your vet. Also, you have criticised scientists at least twice in 5 minutes. I am not pro cull and I do not believe the evidence supports culling badgers, even in the case of your farm. I do hope you understand that the tone of this video and the content is not in agreement with my views so I cannot be involved. "
We get the picture. Follow the money, and the 'group conformity' to keep zoonotic tuberculosis rolling  - in GB at least.

But if PCR diagnostics is good enough for the Aussies, and results compare very favourably with bacterial cultures in France and also in a privately funded study into zTB in alpacas - [link] why not here too?

Thursday, January 19, 2017


Starting with the Final Report of the RBCT (Randomised Badger Culling Trial) we have heard the oft repeated phrase that the primary, OIE approved screening test for cattle world wide, is missing shed loads of infected cattle. But only in the UK: or at least in parts of the UK. The ISG used modeling and the following hypothesis to concoct a heap of infected cattle on page 140  para 7:4
"Thus, if for example the true sensitivity of the test is 75 per cent, infection will remain undetected in one in four herds with a single infected animal. Given that only one confirmed reactor is detected at the disclosure test in about 30 per cent of breakdown herds, this represents a large number of additional infected herds that may remain undetected."
And from that hypothesis, the ISG's electronic abacus expands the risk to thousands of cattle in hundreds of herds. This was repeated more recently by Cambridge University models - [link] with Dr. Andrew Conlan, ignoring the obvious, and stating unequivocally that:
Around 38 per cent of herds that are cleared experience a recurrent incident within 24 months, suggesting that infection may be persisting within herds.
Not that those tested herds may be experiencing an insidious and constant reintroduction of infection from a non-bovine source? The cynical amongst us would suggest that would stop the funding stream generated by badger TB, stone dead. and that would never do.

 Scientists also, in the time honoured fashion of Not Made Here, ignore work done on actual transmission opportunities from reactor cattle, both in Ireland and GB.

In 1978 and 1988 Eamon Costello and Louis O'Reilly tried in Ireland with such pairings. Six months -[link] of shared feed, water, and air failed to transmit anything at all, and twelve months - link showed early lesions in just 4 out of 10 pairings. Conclusion: transmission in the field from cattle was very difficult.

The 'Pathman' project - [link] reporting in 2007, spent £2.8m trying to do the same and salami sliced reactor cattle into very tiny bits. After taking 1600 samples from that project's candidates and 1000 from a parallel study, they report that all failed to transmit. - [link]

A further overview, also written a decade ago by practising veterinary surgeon, the late John Daykin and Dr. Lewis Thomas also squashes flat, the elusive reservoir - [link] of zoonotic Tuberculosis in cattle.

But still, right up to date, we hear the same sing-song lament from this 2016 Defra tome - [link] Page 9.
Because of the limitations of the test and the nature of the response to the bovine TB bacterium we may miss 20 to 25 per cent of TB-infected cattle using the standard interpretation of the test (these animals are known as false negatives).
Defra personnel tend to ignore research and data which doesn't fit their particular bill, and true to form, they have ignored project SE4500, which examines slaughterhouse cases of TB.

Think about it: if the skin test was missing shed loads of cattle, then that abattoir surveillance - [link] designed for exactly the purpose of finding TB lesions, would be finding the 25 per cent of the annual kill that the skin test missed, would it not? So some 600,000 animals? That 'reservoir' which they seek?

Wind up your calculators dear readers, because there are too many noughts for us in that Defra paper.

But briefly it tells us, that out of 11.1 million animals from TB free herds, passing under the MHS officer's TB inspection microscope 2009 - 2013, just 5,366 samples proved positive for m.bovis. And that is nothing like 25 per cent of cattle, it is barely 0.05 per cent. We cannot find any more details as to whether these samples were from old, walled up lesions, or open active disease. But nevertheless, the figures and evidence from around the world do not support the ISG's and Defra's   mischievous assumption that  'If for example....' the skin test (as used in the UK or parts of it)  is rubbish.

So as cattle farmers, we are grateful to veterinary surgeon Den Leonard, for permission to quote his letter of explanation of the 'skin test' when used regularly  as a whole herd test. The letter was featured in Farmers Guardian January 13th.2017.
"Many people ask for a ‘better’ test for TB, quoting the low sensitivity of the single intradermal comparative cervical test (SICCT) or ‘skin test’ as we all call it. Because it has a low sensitivity it misses some infected animals. However, because so many tests are done on a farm and an area basis, infected areas are soon discovered.

When this happens many thousands of tests are performed in that area, as well as repeatedly on infected premises, which overcomes this issue of sensitivity from an eradication point of view, as the test is given many opportunities to identify the presence of TB.

This is how the test is used across the world very successfully and indeed was how our country virtually eradicated TB when we were managing the badger population density at the same time (before the 1992 Protection of Badgers Act).

However, what is needed more than sensitivity is specificity, and this is where the skin test is the best test. It has a specificity of 99.98%, which means that only 1 in 5000 of the positive test results are NOT positive. If we chose a more sensitive test, then we would reduce the specificity. If we reduced the specificity to 99.5%, which still sounds really good, then 1 in 200 positive results would be incorrect.

An area with perfectly clean cattle in it, or even a farm, would never test clear because of the increased false positive rate.

The skin test can be interpreted in a more sensitive (as in misses less positives), and consequently less specific way, by altering the skin thickness thresholds – what is known as ‘severe interpretation’. Also the gamma interferon blood test is more sensitive and less specific. This alteration in testing is appropriate when you know that infection resides in a herd as you want to ensure you find more truly positive cattle quickly, so you ‘accept’ more false positives during that phase. Using the combination of the skin test, gamma interferon blood testing, and severe interpretation, areas without wildlife infection are rapidly cleared of infected cattle throughout the world.

Farmers get frustrated when positively testing cattle do not show up with lesions. This is because nobody is explaining the test result to them properly, or because myths get perpetuated by people unwilling to understand. This aspect has been covered well in David Denny’s letter.

There is no need for any new cattle tests; we just need better education of stakeholders by the government and by practicing vets.

Den Leonard. Lambert, Leonard and May
From what we've read, perhaps we should start that education process with Defra.

We finished the previous posting with Damien Hirst's cow safe in her hermetically sealed formaldehyde tank. We'll end this one with a coughing badger similarly incarcerated.

 A much better idea for all our cattle, we think.

Wednesday, January 11, 2017

Cattle Health Schemes - an unwanted, unworkable addition.

Various bodies operate cattle health schemes in the UK, and are very enthusiastic about adding a new disease to their piggy bank  disease risk portfolio.
We mentioned this in less than glowing terms in our September posting - [link] with a withering swipe at Chief Vet, Nigel Gibbens, for describing those of us who try and farm cattle in a responsible way in his 'High Risk Area' for TB as 'unlucky'.

We are not 'unlucky' at all. As we said in the that posting, we and our half a million dead cattle, are victims of governmental neglect of the wildlife reservoir of zoonotic Tuberculosis on a monumental scale over many decades.

 But despite the fact that zTB is primarily a spill over disease into cattle, from a maintenance reservoir in an untouchable wildlife source which has acquired cult status, the umbrella organisation CHeCS ( Cattle Health Scheme Certification Scheme) have launched their New Year with a flourish.

They and Defra Ministers describe their new risk assessment for zTB as 'rewarding farmers for good biosecurity'. So how has this risk assessment been prepared?

Working from a list of some very dubious 'factoids', the ESVPS (European School of Veterinary Postgraduate Studies) have developed cobbled together a risk assessment hymn sheet [link] for vets to refer to. At the time of writing, numerous meetings have been held to promote this, but we are unsure whether the pamphlet in the link is the final draft, or a primary. The gist of it however is clear enough. Badgers with TB pose a huge problem for cattle farmers, but 'responsible cattle farmers' will keep them away from cattle.

And once again, Defra have thrown this thorny problem to another outside agency, in this instance a veterinary one, and cobbled together the risk of TB with other uniquely cattle diseases.
And that you cannot do.

To compare TB carried by wildlife and their detritus, with such uniquely cattle problems such as BVD (Bovine Viral Diarrhoea) IBR, (Infectious Bovine Rhinitis) Leptospirosis or Johnes disease etc. is both crass and unhelpful.

 The notes from which the Risk Assessment appears to have been drawn up, are mainly computer generated assumptions and factoids, bearing little relation to actual 'risks' which may practically be avoided on any working cattle farm.

Below we list them, with our interpretations:
1. In high risk areas, farms with herds of >150 cattle are 50% more likely to suffer a bTB outbreak than those with 50 or fewer

2.In herds with endemic bTB, herd sizes >300 are likely to circulate disease at a level which may be missed at individual TT test.
That computation is mathematical, not a given. Test 500 cattle in one herd and get one reactor, but test 500 cattle split between ten herds and nine herds will be clear. Simples.

3. Dairy herds tend to undertake higher risk practices including feeding. They also tend to be larger.
' High risk practices feeding Dairy herds’. Are they referring to maize or the way cattle are fed in the shed? Sheds were perfectly O.K until badger numbers got out of hand and used cattle feeding areas as their very own Badger MacDonalds on a regular basis. Grass silage too is mentioned, incurring (shock, horror) a 50% 'risk'. Just what else cattle are to fed during winter months is not explained as 'rough grazing' is also damned, incurring penalties.
4. The risk level can be assessed as highest when groups of cattle are purchased regularly and can be reduced by reducing the frequency of purchase and the size of the groups purchased.
Farmers are trying to run commercial businesses. This document appears to say that farmers should not purchase cattle, or only very occasionally and then  in small numbers. Several of our contributors run 'closed' herds using artificial insemination, have no bought in cattle at all and secure boundaries against any cattle contact. It makes no difference at all to an infected badger. He can infect any cow, any time, whatever its original home.
5. A small scale survey is ongoing to investigate whether reducing the water level in water troughs makes them less attractive to badgers who may not be able to reach in for the water level. This remains an experimental hypothesis at this time.
Experimental hypothesis??? How are smaller calves meant to drink? Via a U shaped straw?
6. Maize is grown on farm or by close neighbours and /or maize silage is fed to cattle leads to a 20% increase in TB risk per 10ha of maize grown.
So the growing of a wonderful home grown source of starch and sugar for cattle feed, is a 'risk', merely because it is also 'valued' as a magnet, by an overprotected pest? Add that to the grass silage and rough grazing previously tabled and cattle are left with precisely what to eat? Thistles?
7. Building access by badgers is recognised as a greater risk than occasional pasture contact.
It doesn't matter how or where cattle come into contact with badgers, if those badgers are infected and infectious at the time of contact and leave behind them infected evidence of their visits. That can be in farm buildings or grazed grass. A reactor is still a reactor. And she's shot.
The infectious culprit continues on its merry way.
8. Badger tracks are recognised as a lower risk than latrine and shared feeding areas at pasture
Badger tracks are still subject to the contents of leaking bladders and scent marking for territorial boundaries. They will use the same tracks too and these lead to 'badger feeding areas' (grassland) containing dung pats etc.. And badgers constantly create new latrines, now that their numbers are so great.
It is not explained how farmers can shrink wrap cattle grazing areas.
9. This [ nutritional deficiencies] may increase susceptibility to TB
That assertion was not born out by the salami sliced post mortems of reactor cattle in the the £2.8m Pathogenesis project - [link]
10. This (above?) should include Johnes disease vaccination if utilised. Using a Johnes vaccine may increase the chances of not detecting infected animals. Work is underway to investigate if the gamma interferon test may be of use in this situation.
Vaccines for Johnes [m.avium paratuberculosis] is not available in UK, as far as we are aware.
11. Evidence to support previous recrudescence or repeated incursions of bTB will need to be looked at in conjunction with the genotype results from infection in SICCT positive cattle.
How about looking at whether badgers have continued and are continuing to visit cattle areas rather than assuming recrudescence via cattle? And if you slaughter out the primary Genotype (should one be found) what happens to number two? Or three? Or four? Cognitive dissonance? No cattle = no TB.
12. There is an odds ratio of 3.1 times greater risk of lifetime risk of becoming a reactor if an individual has at any time tested as an inconclusive reactor.
Not in our, or ex DVMs practical experience over decades. Mathematical models again using assumed data?
13. Even relatively short extensions in the testing interval are associated with an increased risk of disclosing disease in the high risk area.
This will no longer apply as any farmer going over the stated window for his herd's TB testing, automatically has BPS docked and his herd put under immediate restriction. Penalties for any reactors found are also in the pipeline. All certain to focus the mind.
14. If the period of time during the test is prolonged, this can exacerbate the impact of any spread within the herd.
Some extraordinary grammar in that one. A longer time for a vet to test cattle, or a longer period between tests? We'll assume the latter. But if testing periods are extended and exposure has longer to generate lesions (as in four year testing areas) then more lesioned reactors than NVLs would be expected.
15. If this is the case, then local spread from either wildlife or locally purchased stock is suggested. If this is not the case, then purchase from outside the area is suggested.
Spoligotypes will nail that question, without making any more wild assumptions.
16. Byrne et al identified in 2012 that the average maximum distance a badger would roam was 2km. However, under exceptional circumstances hungry animals were found to roam up to 7.5km from their sett, possibly over a couple of days. The risk level can be assessed as highest when groups of cattle are purchased regularly and can be reduced by reducing the frequency of purchase and the size of the groups purchased.
One minute talking about badger ranges and then goes back into stopping farmers purchasing cattle??

And if Woodchester Park's peanut fed pets were used as the guinea pigs for Byrne et al, then forget distance. In the real world, territorial distances traveled are reported to be much, much more. In fact we have been told that one Woodchester badger, collared to track her movements, trundled 21 miles to Bristol Docks. And returned after viewing the estuary. But we don't expect Byrne or et al was told that.

We are told this is an industry led initiative. Really? The names of the AHDB, APHA, DEFRA and the NFU appear as endorsements. Did they really understand what they were suggesting?

We would reiterate, as would our supporting vets, that in no way can the disease zoonotic Tuberculosis carried by over protected wildlife,  be compared in terms of 'risk' with that of genuine cattle diseases, some of which we mentioned above and over which farmers do have an element of control..

So from that list of 'risks', is Damien Hirst's cow offering the only 'safe' place for our cattle to exist?

In a hermetically sealed tank full of formaldehyde, to protect them not only from infected wildlife, but a gravy train of hangers on intent on trousering cash from government negligence?