Sunday, February 18, 2007

SVS has already ruled out infected cattle...

A high profile Tb breakdown was reported this week on the farm of one of the industry's leading government advisors on ... bovine Tb.

During a routine test in december, almost 10 per cent of Bill Madders' dairy cattle were found to be reactors, and subsequently slaughtered, reports

This is another case for those who would defend the badger / villify cattle (and raid the taxpayers' purse) to explain. The article describes the State Veterinary Service investigation as "ruling out infected cattle as the source of the outbreak", and quotes Mr. Madders confirms that he is 99 - 100 per cent certain that a badger sett near his grazing ground is the problem. " Local SVS say it [the breakdown] is almost certainly the result of badger contamination of the pastures last spring", he said.

Mr. Madders now joins the rest of us trying to balance his books with cattle numbers wildly fluctuating, influencing milk or meat output and thus his income, against his business's fixed costs, accentuated by testing all his cattle every 60 days. The cause of the problem, as ever is ignored. Mr. Madders comments that the future of this family dairy farm is in doubt unless he can resolve the problem of reinfection.

"If we are going to keep going down, it becomes uneconomical because we cannot replace the herd witin the levels of compensation currently available".

Mr. Madders was the chairman of the preMT group, but is adamant that the policy should have accompanied with a parallel policy to control bTb in wildlife. "The consistent view coming out of the SVS is that until we do something about the disease in wildlife, it will get worse. It is the politicians we are up against".

"Unless we do get action, the whole country will be infected within a couple of years. In places like the North West, it is going to spread everywhere", he said.

There really is nothing like a herd restriction order, combined with several slaughter notices to concentrate one's mind is there? Our sympathies go to Mr. Madders and his family - and especially to his cattle of course - it's reassuring to have a high profile ally. Mr. Madders will give a background briefing of his breakdown to the TB Advisory group on March 1st. The group reports to Ministers and the CVO - who will probably then ignore the fact that Mr. Madder's farm is surrounded by motorways, rivers or arable land, has had no breakdowns at all in two generations and has been a 'self contained' herd for 20 years.


Anonymous said...

So the SVS blames badgers? Is the same SVS that blamed wild birds for the bird flu outbreak in Suffolk? The same SVS whose senior staff have been blaming badgers for TB for their entire careers? The same vets who said that the skin test for bovine TB was the gold standard? The same SVS whose senior staff were actively briefing against gamma interferon in Defra? Well, I'm sure we can rely on them.

Matthew said...

Don't confuse the foot soldiers of the local SVS offices with the computer led politicos in London who make the noises.
The skin test is used all over the world with no problems at all. It is the primary tool of bTb detection and control. You have a problem with that, go tell the OIE.

We understand Mr. Madders' farm has no cattle neighbours at all, and his brief to Farmers Guardian described a 'self contained' herd.
What part of 'No Bought in Cattle' do you not understand? Sheeesh.

Isabel Davies said...

Great blog (I've given you a plug from Food For Thought):

You may have already seen it, but if you haven't then DEFRA has now published its provisional TB stats for the whole of 2006.

Matthew said...

Thanks Isabel. We appreciate that.

Matt 5

Anonymous said...

From Trevor Lawson, Badger Trust

Matt claims that "The skin test is used all over the world with no problems at all". Why, then, have the following countries (which have failed to control bovine TB with the skin test) introduced gamma interferon TB testing? Australia, New Zealand, the United States, Ireland, Italy, Spain, Portugal ... oh, and Britain.

The skin test isn't working. Today, the Badger Trust has issued a press release revealing that Defra's vets advised Ministers last November that:

"Current tests available are insufficiently sensitive to eliminate the risk of spreading TB through the movement of cattle. The only effective risk management measures are based on strict movement controls."

Matthew said...

Trevor, Trevor Trevor ... they have not 'failed' to control tb, as you so quaintly put it.

According to the OIE site and answers to PQs, the intradermal skin test is the PRIMARY tool for Tb diagnostics world wide. Other tools in the bag may be used, but ultimately for the cattle to comply with OIE Tb-free status, it is the skin test they must pass.

PQs which relate are:
8th Dec 2003 Col 218W [141968] where Ben Bradshaw answered a question on the intradermal skin as a primary diagnostic tool thus:
"The tuberculin skin test has been compulsory in GB since 1950. This is the test prescribed by the OIE for international trade, as well as under EU directive 64/432/EEC..."

and 30th Jan 2004 Col 540W [150492] " All countries that have eradicated, or have a programme to control bTb use one or more forms of the skin test. Government are not aware of any country that has replaced the skin test as a primary test for bovine tuberculosis".

Some countries with an unpolluted atmosphere only use a single bovine jab in the caudal fold, but in the UK and Ireland, a 'comparative' test with avian tb is used - in a slightly cleaner part of the bovine anatomy, the neck.

To clear herds where no wildlife reservoir is involved, gamma interferon may have a place, bearing in mind that its specificity is compromised in that it will pick up shed loads of other bacterium as well as m bovis.

To answer your specific point of why other countries have introduced it; maybe because different strains of m bovis in different countries lurk for different lengths of time.

Countries like Australia and NZ have found it useful as a tool to use ahead of the skin test, because of the length of time m bovis takes to manifest its presence from exposure to flagging up on the skin test.

This is not the case in GB and Ireland, where PQs confirmed that our strains of Tb will show in a minimum of 30 - 50 days ( 6th Jan 2004 Col 251W [ 144437] and a maximum of 226 days (23rd March 2004 Col 689W [ 159074]factors depending on the infective dose route of transmission etc.
However the Australian strains can take up to seven years.(same PQ answer)

In the absence of a wildlife reservoir, and with strains of bTb which take longer to manifest their presence via the intradermal skin test, then yes, a place it may have. Here, it is keeping 'scientists' happy and giving the public and your good self, the impression that they are doing 'something', when in fact the statistics show that the opposite is the case. We do not think you will find the local SVS officers in high Tb incidence areas too enthusiastic over its use, where the primary source of infection, even and especially into 'closed' herds - is not cattle.

Your quote from Defra's 'vets' - Page St? - is probably correct, in that the intradermal skin test is designed as a herd test and not for use on individual animals.
We have explored that long and hard, and favour a post movement test in preference to anything else. But primarily of course, if we sort out the wildlife reservoir, no other add-ons are necessary at all. And we do not, then they will not work anyway.

Anonymous said...

From Trevor Lawson, Badger Trust

Matt: In focusing on Australia you've ignored the fact that other countries, including several in Europe, have failed to control bovine TB using the skin test alone. Even then, if TB can take 226 days to manifest itself, that's plenty of time for it to infect other cattle before the skin test finds it.

Of course no-one has abandoned the skin test. Not only is it required to meet current OIE advice, but the research also shows that gamma interferon delivers best results when used in parallel with the skin test. The point that we make is that the skin test on its own is not effective, particularly in a country like Britain where there is a clear correlation between increased incidence of bovine TB and large average herd size.

OIE advice has not been updated since 2004. Even then it noted the potential benefits of blood based assays, but required more data. That data is now available and whenever the OIE gets around to updating its advice, we can expect to see gIFN getting a higher profile.

Meanwhile, since you're a stickler for references, here's some other scientific research that might interest you:

Carrique-Mas, J.J., Medley, G.F., Green, L.E. 2006. Risk of bovine tuberculosis in British cattle farms restocked after the foot and mouth disease epidemic of 2001. (submitted for publication in the Proceedings of the National Academy of Sciences). The authors used a binomial logistic regression model on VetNet and CTS data to investigate variables associated with TB herd breakdowns on 2,941 cattle herds re-formed after the 2001 FMD epidemic. The three significant risk factors were: sourcing cattle from herds that were tested for TB at least every 2 years, having a history of TB breakdowns on the restocked farm between 1997 and 2000 and increasing herd size.

Christiansen, K.H., O’Keeffe, J.J., Harrington, B.P., McDonald, E.P., Duggan, M.J., Hayes, M.C., McINerney, P., McSweeney, P.T. 1992. A case-control study of herds which fail the tuberculin test six months after being de-restricted for tuberculosis. In: Selected Papers 1992. Tuberculosis Investigation Unit, University College Dublin, pp 45-48. This study found that herds in Ireland which purchased cattle between the clearance test and the six-month check test were twice as likely to fail this test than herds which did not purchase animals.

Collins, J.D. 2006. Tuberculosis in cattle: strategic planning for the future. Veterinary Microbiology 112, 369-381. The author advocates the use of pre- and post-movement tuberculin testing (voluntary or otherwise) for movements of cattle out of herds in known areas of high TB prevalence as a basic principle of preventive medicine and cattle herd health.

Gopal, R., Goodchild, A., Hewinson, G., de la Rua-Domenech, R., Clifton-Hadley, R. 2006. Introduction of bovine tuberculosis to north-east England by bought-in cattle. Veterinary Record 159, 265-271. A detailed investigation into the 31 confirmed TB breakdowns detected between January 2002 and June 2004 in the Northeast of England (old counties of North, South and West Yorkshire, Northumberland, Durham, Tyne and Wear and Cleveland). The affected herds were all in 4-yearly tested parishes at the time of their breakdowns. Using CTS, VetNet and M. bovis typing data, the authors identified purchased cattle (mainly from Wales and endemic TB areas of England) as the most likely source of infection in all but one of the breakdowns. Three breakdowns were traced to cattle imported from Ireland. Some evidence of within-herd spread was found in five herds. In 11 of the breakdowns, the animals that became reactors had originally moved off their most likely source holdings when they were one year old
- 4 -
or younger (10, 12, 13, 14, 15, 20, 261, 299, 400, 400 and 410 days). Such detailed information was not available in another 12 breakdowns, although it was possible to establish that in 7 of those 12 breakdowns the moved animals were less than one year old when disclosed as reactors at the destination herds. This multiple case study provided a concrete example of the potential for young cattle to carry infection and cause TB breakdowns when moved between herds.

Johnston, W., Gettingby, G., Cox, D., Donnelly, C., Bourne, J., Clifton-Hadley, R., Le Fevre, A., McInerney, J., Mitchell, A., Morrison, W., Woodroffe, R., 2005. Herd-level risk factors associated with tuberculosis breakdowns among cattle herds in England before the 2001 foot-and-mouth disease epidemic. Biology Letters 1, 53-56. This paper describes a case-control study of the factors associated with the risk of TB breakdowns in three RBCT areas of southwest England active before the 2001 FMD epidemic (TB99 study). The factors most significantly associated with an increased TB risk were the movement of cattle onto the farm from markets or farm sales, operating a farm over multiple premises and the use of covered yards or other cattle housing types.

Marangon, S., Martini, M., Dalla Pozza, M., Neto, F. 1998. A case-control study on bovine tuberculosis in the Veneto Region (Italy). Preventive Veterinary Medicine 34, 87-95. Identified bought-in cattle as one of the main risk factors associated with the occurrence of TB herd breakdowns in Northeast Italy and concluded that where a region is importing large numbers of cattle from infected herds or geographical areas, a sustained incidence of TB can be maintained in an area without a wildlife reservoir.

McIlroy, S.G., Neill, S.D., McCracken, R.M. 1986. Pulmonary lesions and Mycobacterium bovis excretion from the respiratory tract of tuberculin reacting cattle. Veterinary Record 118, 718-721. Based on the findings from his study, the authors concluded that cattle were the major source of TB in Northern Ireland at the time, with infection derived from purchased cattle accounting for approximately 30% of breakdowns (spread from an infected contiguous herd accounted for 40%).

Mitchell, A., Bourn, D., Mawdsley, J., Wint, W., Clifton-Hadley, R., Gilbert, M. 2005. Characteristics of cattle movements in Britain – an analysis of records from the Cattle Tracing System. Animal Science 80, 265-273. Presents an analysis of the main temporal and spatial characteristics of cattle movements in GB for the period 2001-2003, based on the CTS database. There were several hundred thousand cattle movements from herds in the West of England and in Wales each year, the majority of which remained within those regions (43% of movements were over less than 20 km). Although a substantial number of long-range movements took place, the implication is that, in addition to the risk of transmission from badgers, there is also a real and increased risk of moving infected cattle to other premises within areas of high TB incidence. See also Mitchell (2006), Government Veterinary Journal 16(1), 46-52.

Matthew said...

Too broad a brush stroke Trevor.

The skin test shows the animal's immune response to EXPOSURE to m.bovis - you know that. It does not indicate full blown fulminating infectious status. That, if it occurs at all, comes much later. And in the case of regularly tested cattle, rarely.

Most of the research references you quote are the recent work of the 'magic circle' of ISG members / VLA / Defra whose conclusions we have found lightweight or just plain wrong. Our palette is somewhat wider, having access to the brain power of leading epidemiologists.

Think postulates, Trevor. And in particular 'Evans Postulates', which superceded the Koch Postulates of the late 19th century. And then explore the archive of PQ's and you will see, as did we, that the conditions of this gold standard of epidemiology were satisfied as to transmission and spread of bTb.

The broad brush weilded by the 'magic circle', ignores herds like those of three of our contributers, to whom the ingress of bTb via cattle did not apply. But the breakdowns still cost the taxpayer a packet in extra testing, samples and very dead home bred cattle.

That is why we started this site; to explain that the view being spoon fed (that cattle are wholly responsible for bTb spread) is just plain wrong. And sooner or later, those defending the survival of grossly infected badgers - in which bTb has now become 'endemic' (PQ : 30th. Jan 2004 Col 538W [150508])- will have to explain to taxpayer's, domestic animal owners, parents and other spill-over victims, why.

Matthew said...

Isabel, thanks for the link again. We've posted the very sad end to Richard Bown's dream in a new post.

Blogger changed format over Christmas, and those of us more 'technically challenged', have found the new version very unstable and frustrating to work. Our senior partner, Richard, has had a lot of sorting out to do. Hopefully, posting difficulties and glitches with links are now a bit better.