Tuesday, September 02, 2008

European perspective - SCFCAH

Today the European SCFCAH (Standing Committee on the Food Chain and Animal Health) met to discuss, amongst other things, an ....
"Exchange of views on measures which may be required to prevent the spread of bovine tuberculosis from areas with a high prevalence of the disease via intra-community trade in live cattle: outcome of the working group of 2 September.(MZ)"

They could start by making sure that a maintenance reservoir of disease is not allowed to flourish amongst the tuberculin-tested cattle sentinels in GB. That would be sensible, as they outlined in this document which we posted in July. The responsibilities of EU member state governments with regard to such reservoirs are described quite clearly. One would assume that not even Defra could misunderstand them, but on the experience of the last decade, one would be quite wrong..
... in order to address the role of infected wildlife in the persistence of TB [measures] should be implemented without any delay so as to allow the progress of the eradication programmes. Removal of wildlife, either proactively or reactively following outbreaks, has proven to be an effective ancillary, and in certain situations necessary, measure to control and eradicate TB.

and to reinforce the point:
The elimination or reduction of the risk posed by an infected wildlife reservoir enables the other measures contained in the programme to yield the expected results, whereas the persistence of TB in these wildlife populations impedes the effective elimination of the disease.

Major socio-political resistance (lobbyism) against any measure involving the removal of infected wildlife or interventions affecting the environment are to be expected. The additional costs associated with these actions are not likely to be negligible."
As we pointed out before, the costs of not removing an infected wildlife reservoir are infinitely greater, both in straight monetary terms or the long term transmission opportunities afforded to the many and increasing spillover victims. But Defra's figures for TB incidence in GB in the first five months of the year are appalling. In fact they are a damned disgrace, with cattle slaughterings up a staggering 42 per cent, and confirmed new breakdowns increasing by almost 200 herds. Herds under TB restriction due to a TB breakdown, increased from 4391 in 2007 to 5209 this year.

(Note: The link to Defra website for the May 2008 figures will automatically update when later figures are available. )


Farmers Guardian reports that early indications from the SCFSAH meeting in Brussels suggest that the European Commission has decided against adding further restrictions to UK cattle exports despite European fears that TB could be spread to the continent. But the cattle industry and Defra cannot breath easily yet, as the committee are said to be considering the risk of TB-infected exports at a meeting in October.

So while SCoFCAH monitor the situation without further sanctions at present, official trade restrictions demanded by the Dutch and Belgian veal importers, already imposing their own unofficial boycott, in the short term, have been avoided.

And 'short' is the appropriate word, as cattle slaughterings and herds under TB restriction mount. A week maybe a long time in politics, but a month is very short time span indeed in the life cycle of the bacterium quite misleadingly known as micobacterium bovis. This autumn's casualties are already in the pipeline.


Anonymous said...

Could you please explain your statement "the bacterium quite misleadingly known as micobacterium bovis"?

I thought bovine TB was a worldwide disease of cattle

Matthew said...

Anon 12.51 said:
"I thought bovine TB was a worldwide disease of cattle"

No. That is a common misconception. It is a zoonosis which can affect any mammal, including and especially human beings. All countries test, and slaughter cattle which react to the test, to protect human health. In some countries the disease is found in wildlife, and in most instances such countries control to eradicate the disease in wildlife. We do not, and a substantial spillover into other mammals including domestic pets and their owners is the result..

Recent research has shown that the ancestral DNA of the bacterium christened 'm.bovis' last century, has been found in Egyptian mummies which date from 3500BC. This predates the human form of tuberculosis, also found in Egypt, by 2000 years.

Molecular geneticists say that analysis of recent work suggests that true TB in cattle was eliminated by the 1970s and what we have now, is badger-adapted TB spreading back into the environment.

Anonymous said...

"Molecular geneticists say that analysis of recent work suggests that true TB in cattle was eliminated by the 1970s and what we have now, is badger-adapted TB spreading back into the environment."

where are the references for this? sounds like interesting reading.

Anonymous said...

Anon 12.51 said:
"I thought bovine TB was a worldwide disease of cattle"

Matthew replied:

No. That is a common misconception. It is a zoonosis

Yes it is a zoonotic disease but 'the common misconception' would also seem to be held by the OIE who list bovine TB as a cattle disease.

The OIE is the intergovernmental organisation responsible for improving animal health worldwide.

It is recognised as a reference organisation by the World Trade Organization (WTO) and as of January 2008, had a total of 172 Member Countries and Territories. The OIE maintains permanent relations with 36 other international and regional organisations and has Regional and sub-regional Offices on every continent.

But of course Matthew knows better

Matthew said...

Anon 9.35.
It was always assumed that bTb was an offshoot of what is known as 'human' tb, or m.tuberculosis. But recent work published in a subscription mag. indicates this may not be the case. Ancestral DNA of bovis predates human form by 2000 years, and has been isolated from Egyptian mummies. The abstract is below. The overeview is from an epidemiologist who has the paper, and sent us the abstract:

Research Article
Molecular history of tuberculosis from ancient mummies and skeletons
A. R. Zink 1 2 *, E. Molnár 3, N. Motamedi 2, G. Pálfy 3, A. Marcsik 3, A. G. Nerlich 2
1Department of Earth and Environmental Sciences, LMU Munich, D-80333 München, Germany
2Division of Palaeopathology, Institute of Pathology, Academic Teaching Hospital München-Bogenhausen, D-81925 München, Germany
3Institute of Anthropology, University of Szeged, H-6722 Szeged, Hungary
email: A. R. Zink (albert.zink@lrz.uni-muenchen.de)
*Correspondence to A. R. Zink, Department of Earth and Environmental Sciences, LMU München, Theresienstr. 43, D-80333 München, Germany.

ancient DNA • M. tuberculosis • evolution • PCR • genotyping


The origin and evolution of the infectious disease tuberculosis (TB) and its pathogens is still not fully understood. An important effort for a better understanding of the underlying mechanisms of TB evolution lies within the investigation of skeletal and mummified material dating back several thousand of years. In this work, molecular data from mummified and skeletal material from different time periods of the Old World are compared, and the current status of ancient mycobacterial DNA analysis in ancient human remains is discussed, with particular reference to the genetic evolution of human TB. The molecular analysis of material from southern Germany (1400-1800 AD), Hungary (600-1700 AD) and Egypt (3500-500 BC) revealed high frequencies of TB in all time periods. In several individuals from ancient Egypt the mycobacterial DNA could be further characterised by spoligotyping. Thereby, evidence for ancestral M. tuberculosis strains was found in the pre- to early dynastic material from Abydos (3500-2650 BC), while typical M. africanum signatures were detected in the Middle Kingdom tomb in Thebes-West (2050-1650 BC). Samples from the New Kingdom to Late Period tombs (1500-500 BC) were characterised as modern M. tuberculosis strains. In concordance with other studies on ancient skeletal and mummified samples, no evidence for the presence of M. bovis was found. These results contradict the theory that M. tuberculosis evolved from M. bovis during domestication, but supports the new scenario that M. tuberculosis probably derived from an ancestral progenitor strain. Copyright © 2007 John Wiley & Sons, Ltd.

Anon 11.42
Pedantic barbs won't stop this disease of mammals spreading from its maintenance host, the badger. And it doesn't make a 6-9 month course of a cocktail of drugs with particularly nasty side effects, any easier on those unfortunate enough to encounter it. That's if they are diagnosed in time.
OIE - Office of International Epizootics - diseases which affect animals and humans.

Anonymous said...

thanks for the reference!

you say:

"It was always assumed that bTb was an offshoot of what is known as 'human' tb, or m.tuberculosis. But recent work published in a subscription mag. indicates this may not be the case. Ancestral DNA of bovis predates human form by 2000 years, and has been isolated from Egyptian mummies."

Actually, the paper doesn't say that at all.

First off, the original hypothesis was that bovis predated tuberculosis and the (primarily) human pathogen arose from bovis around the time of domestication of herd animals

Second - these scientists failed to isolate ANY M bovis DNA from the ancient samples (although they did state that due to m bovis having a lower copy number of the marker they were looking for m bovis may have been missed).

They go on to conclude that there was an ancestral mycobacterium similar (which they found evidence of) to the modern M tuberculosis (which they did isolate) and that the other pathogenic strains (bovis and africanum) were derived from that strain.

it is a very interesting bit of research.

Matthew said...
This comment has been removed by the author.
Matthew said...

Anon 10.02.
Sorry for the confusion. We quoted from two pieces of work, gave reference for one and a combined overview. The other is:

"A new evolutionary scenario for the Mycobacterium
tuberculosis complex."
R. Brosch*, S. V. Gordon†, M. Marmiesse*, P. Brodin*, C. Buchrieser‡, K. Eiglmeier*, T. Garnier*, C. Gutierrez

Put simply, - and we have to do this as we are taking very detailed and complex information from people who know about these things - organisms within the tuberculosis complex, including m. tuberculosis and m. bovis, instead of evolving one from the other fairly recently, came from the same ancestral progenitor strain which produced 'branches' several thousand years ago.

This work (Brosch) explains that these 'branches' have remained distinctly separate and are identifiable by lost chunks of DNA. However some (human) strains still retain ancient ancestral m. tuberculosis characteristics.

Thus although strains of both m. bovis / m. africanum complex and some of the m.tuberculosis are occurring in parallel time frames, going back much further, the paper above (Brosch) concludes with the following observation:

"More insight into this matter could be gained by RD
analysis of ancient DNA samples, e.g., mycobacterial DNA
isolated from a 17,000-year-old bison skeleton (19). The Mycobacterium whose DNA was amplified showed a spoligotype that
was most closely related to patterns of M. africanum and could
have been an early representative of the lineage M. africanum3/
M. bovis. With the TbD1 and RD9 junction sequences that we
supply here, PCR analyses of ancient DNAs should enable very
focused studies to be undertaken to learn more about the time
scale within which the members of the M. tuberculosis complex
have evolved."

From the diagrams within this work, from a single ancestral progenitor strain, several strands evolved and m. canettii, and the m.africanum / m.microti / m.bovis (RD9) line separated and predated the more modern m. tuberculosis strains.

This paper also points out the M.bovis complex appears very 'species adaptable', showing "natural host spectra as diverse as humans in Africa, seals in Argentina, goats in Spain and badgers in the UK." (Interestingly they do not mention cattle)

They continue "For this reason it is difficult to imagine that the spread and adaptation of RD-9 deleted bacteria to their speciic hosts, could have appeared within the 15,000 - 20,000 years of specification of the M.tuberculosis complex."