Thursday, November 02, 2006


The map of GB bTB outbreaks, as determined by the spoligotyping ferrets at VLA, is not - as one would expect if cattle to cattle transmission and cattle movements were the primary cause of the disease, - like a kaleidoscope of scattered strains. We have updated the post below: to show the results of a thirty year survey which concludes:

"In general the spoligotype and VNTR patterns obtained from badger isolates between 1972 - 1976 were the same as those observed in the same geographical areas today. This suggests that the geographical clustering of strains has not changed since the first isolation of M.bovis from badgers over thirty years ago."

The results of the geographic spoligotyping excercise on reactor cattle is below:

Type 9 isolated in 44% Cornwall/Devon 20% Dyfed

Type 17 " 66% Here /Worcs / Glos.

Type 21 " 74% Somerset / Avon

Type 35 " 77% Here / Worcs /Shrops.

Type 10 " 79% Glos.

Type 25 " 79% Staffs / Derbys.

Type 22 " 84% Gwent / Here / Worcs.

Type 15 " 89% Cornwall

Type 11 " 93% Devon / Somerset

Type 12 " 94% Cornwall

Type 20 " 95% Cornwall

So, up to 95% of m.bovis isolates identified from reactor cattle, are identical to the strains identified and persisting for over thirty years in ....... badgers indigenous to the same geographical area? Yup, they are.

We accept that the 5 - 25 per cent of isolates identified outside their indigenous home deserve attention, but what about the cause of up to 95 percent - which is getting absolutely none?


Anonymous said...

From Trevor Lawson, Badger Trust.

The Badger Trust would like to respond to two issues raised on this blog: spoligotyping and pre-movement testing.

It has been argued that if cattle movements were responsible for bovine TB transmission and persistence, you would expect to see an even spread and density of spoligotypes across the country. It has also been claimed that the apparently low number of infected stock identified by pre-movement tests proves that cattle have not been spreading bovine TB.

In both cases, these claims result from a misunderstanding of the data.

The simplistic argument that spoligotypes should be more evenly mixed in the national herd pre-supposes that cattle movements are evenly distributed. They are not. Evidence presented at TB meetings for the last two years shows that 86 per cent of cattle movements are in the same TB hotspot. Therefore, you would expect to see pooling of each spoligotype and that is exactly what happens.

Since the latest research from the Krebs trial also shows that cattle transmit TB to badgers very quickly, the pooling effect is likely to be mirrored in badgers.

In his blog, Matthew quotes a single paragraph from research project SE3020 and draws a conclusion from it that is not made by the authors themselves. Whilst they note that spoligotype patterns are "in general" the same, they point out that:

"the restocking of herds had resulted in the introduction of M. bovis isolates with spoligotypes that had not been seen in these areas of the country before. These data were used to underpin a policy of pre-movement testing of cattle to prevent movement of infected animals, especially those that are to be moved from areas of the country that are at high risk of M. bovis infection to areas of low risk for the disease".

So, whilst Matthew deduces that the evidence shows that cattle movements were not significant, the authors draw the opposite conclusion.

Matthew also fails to mention another very serious finding that should be of concern to all farmers. The authors note that:

"results indicate that clonal groupings of M. bovis share distinct phenotypic characteristics, possibly cell wall differences, that may result in differences in virulence, transmission or ability to evade the tuberculin skin test".

For those farmers who have been told by the SVS that badgers are to blame for repeated TB outbreaks, consider the significance of this finding. It means that the skin test might successfully find some strains of TB, but miss others. This is supported by evidence that confirms that the skin test misses around 33 per cent of infected animals in a herd.

This makes evolutionary sense, too. Year after year of testing will remove cattle infected with spoligotypes that the skin test finds easily, but better hidden, genetically mutated spoligotypes will evolve and spread precisely because they are better at avoiding the test.

Another important factor is that more than 50 per cent of the TB testing effort in England and Wales is focused on just four per cent of herds. This shows that the bulk of the TB problem is concentrated in specific problem herds (and gamma interferon testing should help to address this). But it also corresponds to the pooling effect described above.

Matthew draws the conclusion from SE3020 that the primary home of each spoligotype is "badgery". But he ignores the authors own statement:

"These observational data support the hypothesis that transmission occurs between the two host species; however they could not be used to evaluate the relative importance of badger-cattle and cattle-badger transmission."

The second argument postulated is that the small number of cattle so far found by pre-movement tests proves that the testing is unnecessary and that cattle movements have not played an important role.

But the "pre-movement test" data from Defra do not include normal annual tests that have been moved to just before a planned movement of livestock, in order to avoid the cost of repeat tests. Since the "pre-movement" data is wholly incomplete, the conclusions drawn by Matthew are meaningless.

The scientific evidence that is emerging is very significant and paints a far more complex picture than Matthew would have us believe. It also shows that eradicating bovine TB is impossible given the control mechanisms currently available. Badger culling only inflames the situation and would cause immense damage to the public's perception of and support for farmers.

So, smart farmers will protect their own badgers and support better TB testing.

The Badger Trust believes that only a minority of farmers think that badger culling will work, as evidenced by how relatively few farmers actually responded to the Government's consultation (despite being encouraged to do so by the NFU) and our own contact with farmers on the ground.

Matthew said...

Forgive the delay in answering your post Mr. Lawson.You claim we 'misunderstand the data', citing "evidence presented at TB meetings for the last two shows 86 percent of cattle movements are in the same TB hotspot". Your source?

Without a source for that information, it is impossible to quantify its context, but if past experience of data hoovered up by attendees of TB meetings, and then regurtitated back to a gullible public, out of context or just plain wrong - 14 million animal movements? - we cannot comment.
If however those 86 per cent of movements are within counties, which may have the same ISG identification number, then be aware that from the data published in this paper, most counties have at least two m.bovis spoligotypes and some have three, in distinct geographic areas.

We do not "deduce that cattle movements are not significant", in fact we do not 'deduce' anything. But the authors of paper SE3117 may do.
They state in their assessment of cattle - cattle Tb that following "initial investigations via CTS, results for 2002/03 (which included post FMD whole herd restocks) 25 - 85 percent of all breakdowns could have been caused by badgers".

Post FMD, any Tb problems would have been found at a post-movement test, (which is what we have been calling for, for over ten years)But the point is, they were found. By the skin test. Slaughtered out. End of problem. The authors of the paper are correct in their conclusion that the observational data which we showed (of the same spoligotypes in two host species for 30 years in the same geographical area) cannot be used evaluate badger - cattle and cattle - badger tramsmission. But combined with CTS cattle movement data, and pathological data of the candidate animal's ability to sustain onward transmission, it is very important.
Unless cattle have open lung lesions, which very few have, (SVS source) then onward disease transmission either to other cattle or anything else is unlikely (Ref: Drs. R. Clifton-Hadley & J. Gallagher)

It is the other end of the scale of up to 85% herd breakdowns that the Badger Trust would ignore, and which has affected the authors of this site with such devastation.

That cattle transmit Tb to badgers very quickly (after FMD - and "there can be no other explanation")are the latest outpourings from Rosie Woodroffe. We have posted on the site. 2 + 2 in this case, do not make 4. See below for what happens to your badgers if their food source disappears.

You say we have ignored the "clonal groupings" and "differences in virulance, transmission or ability to evade the skin test" part of the paper.
Not at all. But we take it in the context of UK AN5 being the root strain for worldwide PPD tuberculin antigen since 1948, of cattle prior to 1975 being tested quite satisfactorily with human Tb strains DT, C and PN and post 1975, with a product that PQ's confirm has enabled, "in the absence of a wildlife reservoir", most of the rest of the world to consign this dreadful disease to history.

But in every cloud, there is a silver lining, and we have described the 'benficial crisis' this level of bTb has spawned many times - including 'research'. So it is no surprise to find lurking in the paper under discussion, this gem: "M. bovis AN5, a strain originally isolated in England c 1948 and is used world wide for bovine PPD production. However the spoligotype and VNTR profile of this strain is not shared by any extant strains in the dtabase. This raises the possibilty that AN5 strain may not be optimal for the detection infection of M. bovis strains currently prevalent in GB and highlights further work should be done to resolve the matter”

So having said the strains today are the same as thirty years ago, and in the same areas. And that AN5 is used all over the world as a PPD base, and prior to 1975, human tb m tuberculosis strains DT, C and PN were used at VLA for bovine diagnosis, with it has to said pretty good results, the VLA spoligotyping team would like “further work to resolve the matter” of AN5's efficacy.
I’m sure they would.

Re: Pre Movement Testing. We quote Defra's figures. We are not happy with the dangerous complacency or cost a pre movement test invokes and note that the R of Ireland withdrew them in 1996. A post movement test of all breeding cattle we would support.

Slaughterhouse cases of cattle which the skin test has not picked up, at 247 confirmed (Aug figures) out of an annual cull of 3.4 million animals, all inspected both by vets and MHO staff at slaughter, is not indicative of the 'huge reservoir' of infected cattle attributed by the Badger Trust to be spreading the disease far and wide.

That "50 per cent of the testing is focused on 4 per cent of herds" is again a meaningless figure unless a source/context is given.

If you mean that herds are not getting clear after repetitive 60 day testing, then after five very long ones (years) I would agree. But we had no 'Bought in Cattle either.

You say "Scientific evidence emerging is significant". We do hope that you are not including anything from the the Krebs Badger dispersal trial in that context?

And this 'smart farmer' did just that. No bought in cattle, and a healthy respect for 'our badgers'. Unfortunately that comfort blanket disappeared when 'our' badgers became infected and Bourne's badger dispersal teams stirred the whole lot up, leaving social groups shattered and the area heaving with sick, stressed and very infectious badgers.

400 head of cattle on five farms down this valley paid the ultimate price of this prevarication. As did the hundreds of dead badgers found on roads and in fields in various states of emaciation.

Mr. Lawson, when herds like those belonging to the contributers to site, go under continued bTb restriction, and 'No bought in Cattle' appear on their TB 99's, it is up to those denying the role of the badger to hypothysise an alternative source of infection.