Pembrokeshire against the Cull

PAC, PO Box 65, Cardigan SA43 9AD

PEMBROKESHIRE AGAINST the CULL

ATAL y CWLIO SIR BENFRO

Contents:

Definitions

RBCT

ISG

WAG

IAA

The Badger (Control Area) (Wales) Order 2011

Perturbation

TB

Excretors and super-excretors

Confirmed and Unconfirmed breakdown

Questions and Answers

General

What is Bovine Tuberculosis?

What is the risk to human life?

Is Bovine TB found in other animals?

Is Bovine TB increasing in the IAA?

Culling

What is the proposed cull in Wales?

Surely we have to do something?

But we need a holistic approach to TB?

Why can culling not be used in any TB hot spot?

Is the IAA a suitable area?

But the cull would reduce TB in cattle in the IAA?

Why do you say culling will only reduce 'confirmed' TB cases?

Can't we just kill infected badgers?

Don't most landowners in the IAA support the cull?

If most landowners will grant access, why force entry?

Didn't the King Report show that culling is justified?

Doesn't the Thornbury cull prove that culling works?

Vaccination

Isn't it true that vaccination won't work on infected badgers

Could vaccination work in a population with 30% or higher TB?

So DO 30% of badgers in the IAA have bovine TB?

Would a high level of badger TB favour a cull?

Won't sick badgers keep spreading the disease?

Isn't culling better proven than vaccination?

But still, vaccination is unproven?

Won't vaccination take much longer than culling to work?

Definitions:

RBCT

The Randomised Badger Culling Trials (sometimes called the Krebs trials) were a detailed study carried out in England to assess whether badger culling was a viable method of controlling bovine TB. The supervising scientists concluded that "badger culling cannot meaningfully contribute to the control of cattle TB in Britain" and recommended a raft of cattle control measures instead.

ISG

The Independent Scientific Group on Cattle TB were the scientists who supervised the RBCT trials. Among others these included:

Professor John Bourne, Chairman and veterinary medicine expert

Professor Christl Donnelly, Deputy Chairman and epidemiologist

Professor Rosie Woodroffe, ecologist

All three of these have spoken out against the current proposed culls.

WAG

The Welsh Assembly Government. Not to be confused with the Welsh Assembly (the elected Assembly members) this is the organisation that would be running the cull in Pembrokeshire.

IAA

The Intensive Action Area (map here) is an area of 288 km2 mainly in North Pembrokeshire. An area of high bovine TB, WAG have already introduced stricter cattle based measures in the IAA - and indeed TB statistics in the area do seem to show a significant and steady drop since 2008, although it is early to conclude whether this is a blip or the start of sustained reduction in TB.

This is the area where WAG propose to force entry onto private land to slaughter badgers, for at least the next 5 years - although the draft legislation places no upper limit on how long the slaughter or the right to force entry would persist.

The Badger (Control Area) (Wales) Order 2011

This is the piece of legislation that gives the Welsh Assembly Government the right force entry onto private land to slaughter badgers, and makes it an offence to do or say anything that might interfere. The full text is available here.

Perturbation

In the UK, at least, badgers tend to live in family groups in small, well defined territories and don't naturally travel very far from home.

It was found that culling disrupts this, causing badgers to roam much further afield. It is thought that this gives them much more opportunity to catch TB from or transmit TB to other badgers or cattle.

The observed effect is that TB goes up in badgers in the culled area, and in cattle in the surrounding area. This effect, and the increased range of badgers, is referred to as 'perturbation' or 'the perturbation effect.'

TB

'TB' in this document refers to 'bovine tuberculosis', a disease caused by the organism M. Bovis, which can in principle infect any mammal, and notably cattle, humans and badgers. Most tuberculosis in humans in the UK is caused by a related organism, M. Tuberculosis. Since the advent of pasteurisation of milk, bovine TB is only a health risk to those working with infected animals.

Excretors/super-excretors

Not all badgers who are infected with TB are found to excrete detectable levels of TB. Those that do (often sporadically) excrete detectable levels of TB are referred to as 'excretors.' Those badgers who are found to excrete bacteria in largest numbers or most often are referred to as 'super excretors.'

Excretors and super excretors are in the later stages of the disease and are likely to have significant health problems such as visible lesions in their body.

During the RBCT, 16.6% of badgers were found to be carrying TB, but only about 1.6% of the badgers culled were found to be super-excretors.

Confirmed and Unconfirmed breakdown

A 'breakdown' is an incident in which an animal, usually a cow, tests positive for TB in a herd that was previously clear of the disease.

This means that the whole herd is under stricter controls, whether one cow or several tested positive, so we generally refer to a 'herd breakdown.'

Cattle who are tested positive are called 'reactors', and are sent to slaughter where further tests look for visible 'lesions' in the body, caused by the advanced stages of TB infection, and try to culture TB from samples taken from the body. If either lesions are found, or TB is successfully cultured, that reactor would be termed a confirmed reactor

A herd breakdown where at least one of the reactors is 'confirmed' is a 'confirmed breakdown.' If none of the reactors are confirmed, it is an unconfirmed breakdown. An unconfirmed breakdown is not necessarily a case of a healthy cow being wrongly diagnosed with TB. Veterinary opinion is that the vast majority of these cases are simply cattle who were caught very early in the progress of the disease, and so have no lesions and little TB present.

Questions & Answers

General

What is Bovine Tuberculosis?

Bovine Tuberculosis is a disease caused by the organism Mycobacterium Bovis, best known for its effect on cattle and humans. Its name comes from the formation of lesions or 'tubercles’, most often in the lungs although other organs can be affected.
It is most easily caught through the respiratory tract, by breathing in bacilli shed by coughing animals, or through the alimentary tract, such as by humans drinking infected milk or badgers foraging for insects in infected cowpats. In cattle, the respiratory tract is the most common route of infection. In humans drinking infected milk is historically the most common route, although pasteurisation has largely eliminated this risk.

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What is the risk to human life?

Humans can catch the disease, most easily by drinking contaminated unpasteurised milk. Since the advent of widespread pasteurisation, only those people working with infected animals are at risk. Most famously a researcher working at the UK's FERA badger research facility at Woodchester was suspected to have contracted bovine TB in 2009.
While resistant to some common tuberculosis drugs, it is treatable.

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Is Bovine TB found in other animals?

In 1971 bovine TB was found to be present in a dead badger from an infected farm. This was the first time that the presence of bovine tuberculosis was suspected. Further testing showed that the disease was present in many wild badgers, leading to the assumption that badgers were the source of many, if not most, bovine tuberculosis outbreaks and should therefore be culled to contain the disease.
Since then we have learned that most mammal species are susceptible to bovine tuberculosis, including rats, foxes, deer, goats, sheep, cats and dogs.

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Is Bovine TB increasing in the IAA?

During the debate on the annulment of the Badger Control Area Order Elin Jones claimed that TB was increasing in the IAA on the grounds that the number of new herd breakdowns had increased from 55 in 2009 to 79 in 2010. But why quote herd breakdowns, which can be anythng from one cow found with TB to hundred? Why quote new herd breakdowns?

According to the figures released by WAG the total number of cattle being slaughtered for TB in the IAA has been dropping since 2008. This is arguably a more reliable statistic.

Cattle slaughtered in IAA for TB
2005 - 692
2006 - 749
2007 - 948
2008 - 1,725
2009 - 1,528
2010 - 850

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Culling

What is the proposed cull in Wales?

According to the "Badger (Control Area) (Wales) Order 2010" WAG is granted the right to force entry onto any land in the Intensive Action Area in order to slaughter badgers.

This would take place for a couple of weeks, once a year for at least five years, although the proposed legislation places absolutely no upper limit to how many years this could be continued. Badgers would probably be caught in cages and shot, although this legislation also allows the possibility of shooting badgers not trapped in cages - a culling method that has not been tested during the RBCT trials. WAG claim they will not be exterminating all badgers in the area, only about 70%. However the RBCT trials achieved a 70% reduction in badger numbers with only about 70% land access (see the ISG's Final report, Land access cited on page 46 paragraph 2.49, badger activity reduction cited on page 19 paragraph 5.) As WAG, based on the 2009 cull, are pushing for 100% land access it is likely that the impact on the badger population will be significantly higher, assuming similar trapping efficiency.

Landowners do not have to give their consent to this slaughter, and many oppose it vociferously. In principal contractors will give reasonable notice of when they would be coming onto land and would identify themselves when they did so. However when WAG attempted a cull in 2009, 'reasonable notice' often consisted of being told on the day when they turned up or only being informed after the event, and 'identification' consisted of masked men showing cards with a photograph (allegedly of their faces, although they would not remove their masks to allow this to be verified) and a number that could be 'verified' by calling WAG.

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Surely we have to do something?

Of course. We don't advocate doing nothing, we advocate vaccinating badgers instead of slaughtering them. This not only a more humane option, but it is also cheaper, can be deployed in any TB hot spot whereas culling can only be used in suitable geographical areas, and does not require the breaches of civil liberties required by culling.

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But we need a holistic approach to TB?

'Holistic' has emerged as a favourite buzzword for politicians defending a cull.

Statistics for the IAA suggest that the current approach is working just fine. A holistic approach may be even better, but is arguably not 'needed' to the extent of justifying breaches of civil liberties, for example.

In any case a true 'holistic' approach would treat the whole system, so reduce TB in both the badger and the cattle population. WAG themselves state that the cull is not expected to reduce the prevalence of TB in badgers, and experimentally culling is shown to be likely to increase TB in badgers, whereas a vaccination programme clearly would reduce TB in badgers.
So a vaccination programme is more truly a 'holistic' approach than a cull would be.

Holistic: "relating to or concerned with wholes or with complete systems rather than with the analysis of, treatment of, or dissection into parts" from the free Merriam-Webster

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Why can culling not be used in any TB hot spot?

Culling badgers causes 'perturbation', spreading TB to surrounding areas. So even pro-cull advocates admit that it can only be used in areas surrounded by 'hard boundaries' such as coast, large rivers or motorways which will prevent badgers from moving in and out of the area.

The perturbation effect also means that culling will be more effective if done on large areas, to maximise the area where beneficial effects are seen and proportionately minimise the area around the edge where harmful effects are seen.

So a cull can only be deployed where you have a large area which is a TB hot spot and is surrounded by 'hard boundaries.'

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Is the IAA a suitable area?

Probably not - the coast and the Teifi river as far as Cardigan are reasonably hard boundaries. However the remainder of the boundary is arguably very permeable to badgers. A recent study used genetic evidence to show that while large, wide rivers and motorways formed effective barriers to badger dispersal, smaller roads and rivers did not.

Indeed many of the boundaries have been chosen simply to be woodland or sheep farming areas. In other words badgers will move freely across the boundary, but there will be no increases in cases of TB in cattle to show for it. While that is a good thing in itself, the perturbation effect also resulted in a massive increase in TB in badgers, and there is no reason to believe that woodland or sheep-farming boundaries will do anything to mitigate that effect.

So far from 'tackling the wildlife reservoir' this cull may well massively increase the level of TB in the badger population.

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But the cull would reduce TB in cattle in the IAA?

Compared to doing nothing to badgers, the cull should reduce cases of confirmed TB cases in cattle if carried out at least as well as in the RBCT. But, for example, if the cull is not carried out simultaneously over the whole area, then the effects could be far worse than predicted, possibly to the extent of increasing cattle TB cases. The results promised by the WAG consultation documents are based on those achieved by the RBCT, where the areas were culled in the space of two weeks. It seems unlikely that the IAA (much larger than the areas used in the RBCT) could be culled in that space of time.

If you compare culling to vaccination, rather then to doing nothing, then it is even more dubious whether culling would reduce cattle TB cases. Certainly the reduction would be massively lower than the figures quoted by WAG - especially if you take into account the fact that culling will cause increases in cattle TB just outside the IAA, whereas vaccination would not.

This chart shows the results of a computer simulation of culling, vaccinating and doing nothing to badgers, showing the expected number of cattle herd TB breakdowns over time as a result. It is taken from Annex 9 (page 15 figure 3(A)) of the evidence submitted to Elin Jones to justify the cull, and has been edited to remove two curves that are irrelevant to this discussion, to make it easier to read. Culling or vaccinating began in year 120.

The results shown are the levels of cattle herd breakdowns predicted in Pembrokeshire if either nothing is done to badgers (green line), badgers are culled (brown line) or vaccinated (blue line). It can be seen, despite the scale, that the vaccination option not only has as rapid an effect as culling, but actually produces better results than culling for the expected duration of the cull.

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Why do you say culling will only reduce 'confirmed' TB cases?

This is the experimental evidence from the RBCT. See for example the final sentence of paragraph 5.22 on page 95 of the Final Report of the ISG:

We therefore conclude that there is no evidence of an impact of proactive culling on unconfirmed breakdowns within trial areas and focus our attention on the analyses based on confirmed breakdowns only.

We don't know why this should be, but it does have a significant impact on any potential gains from a cull. According to DEFRA statistics in 2010, in Dyfed (the region containing the IAA) only 167 out of 479 new herd breakdowns (35%) were 'confirmed'.

WAG appear to be dismissing this concern. The Submission to the Minister (paragraph 141 page 26) states that:

Taking into account the disease situation in endemic areas (i.e. that the majority of unconfirmed breakdown herds are genuinely infected with M.bovis) , it is concluded that an effect of proactive badger culling in endemic areas on unconfirmed herd breakdowns should be expected.

It is not clear why WAG dismiss the experimental result - the fact that we do not understand the mechanism does not change the reality. If true, and taking the DEFRA herd breakdown figures for Dyfed as a guideline for the number of confirmed and unconfirmed individual breakdowns, this could reduce an expected reduction of 28% to less than 10%.

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Can't we just kill infected badgers?

WAG have currently rejected this on the grounds that current on-the-spot tests for TB, such as the BrockTB Stat-Pak test used in the vaccine field trial, are not sensitive enough for such an approach to be feasible. Otherwise they would either have to trap the badgers and remove them to a lab for several days for testing before returning them to where they were trapped- a logistical nightmare.

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Don't most landowners in the IAA support the cull?

Again, this is often claimed but never proven. During the last cull WAG claimed that they were granted 'voluntary access' to more than 90% of the land, yet admitted that over 100 landowners had refused access to their land, despite the threat of arrest, and this admission was made long before the most vocal opponents of the cull had been visited. Of course 'voluntary access' might have been meant to include 'access granted under threat of arrest.'

e.g. Dr Glossop,Wales Online

"We have the legal powers to access land, but it is worth noting that by far the majority of landowners are willingly working with us. Over 90% of landowners in the area have co-operated voluntarily."

Farmers Weekly "Welsh Farmers Block Badger Cull":

"About 100 farmers within Wales' badger cull zone are refusing to allow Welsh Assembly officials on to their land just days before the first badgers are likely to be trapped."

PAC later found more than 300 landowners in the area (out of ~1500) willing to sign the open latter against the cull - and almost as many opposed to the cull, but unwilling to sign a public document for fear of reprisals.

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If most landowners will grant access, why force entry?

This raises another point - the submission to the minister (paragraph 105) claims that the cull, in order to meet the minimum requirements to be effective, needs "land access compliance of greater than 60%" but that the difference in effectiveness between a cull with 70% land access and 100% land access is 'small'. Yet if they genuinely have voluntary access to more than 90% of the land, then they do not need the draconian right to force entry to opponents' land.

If they do need the right of forced entry, it is because WAG and the minister have misled the people of Wales, and the Assembly, about how much land is voluntarily opened to the cull.

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Didn't the King Report show that culling is justified?

The 'King Report' is a curious document. It did indeed conclude that culling was justified, but the way this report came about casts some doubt on its impartiality.

As stated above, in 2007 the RBCT trial's final report, as written by the scientists involved in the study, was published and concluded that "badger culling cannot meaningfully contribute to the control of cattle TB in Britain."

The UK Government Scientific Advisor at the time, Sir David King almost immediately published his own report. He had not been involved in the study, and his field of expertise, surface chemistry, is not obviously relevant to this subject. He spent ~10 hours talking to 5 experts in relevant fields, but who had not been involved in the study, then published what looks like his own final report contradicting that of the scientists who supervised the RBCT, and is often presented as the results of the RBCT trials.

For more information, including the response of the scientific community to the King report, see the PAC science pages.

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Doesn't the Thornbury cull prove that culling works?

Debatable. Certainly there was a dramatic drop of TB in the Thornbury area after the cull, but there is some doubt whether this drop was related to the cull. This graphic seems to show that the drop started years before the cull did. Since there was no control area in this study, it is impossible to be sure that the cull had any influence on the continued drop after culling started.

Also, the Thornbury cull used a different culling method and culled essentially ALL badgers in the area. Since the Welsh cull cannot legally use gassing or 100% extermination, the Thornbury trial is not that relevant to predicting results.

Similar arguments apply to the other culling trials occasionally cited as 'proof' that culling works. For a more detailed discussion see Martin Hancox's excellent site.

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Vaccination

Isn't it true that vaccination won't work on infected badgers?

It is true that vaccination won't have any benefit for infected individuals, but it does not mean that vaccination won't work on a population with some infected badgers. WAG themselves have published computer modelling studies showing, if only in simulation, vaccination working on infected populations.

Even according to WAG only 30% of badgers in the area are infected, implying that 70% are not. So vaccination, by protecting the healthy population, will still be effective in a hot spot. Indeed studies published by WAG clearly showed that vaccination would be most effective (in terms of number of cattle TB cases prevented) when used in areas of high TB.

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Could vaccination work in a population with 30% or higher TB?

A recent study showed a 74% reduction in the new incidences of previously healthy badgers testing positive to an antibody test for bovine TB when they were vaccinated. As the antibody test is less sensitive to badgers in the early stages of TB, at least part of this reduction is likely to be due to the vaccine reducing the severity of, but not completely preventing, infection. However, from the point of view of reducing the infectious shedding of bacteria by badgers, this is still excellent news.

To measure this the experimenters first had to reject any badgers that already had, or were suspected of having bovine TB, and a staggering 43% failed this test. This was a deliberately stringent test - the researchers were prepared to reject a few badgers who might be healthy in order to be as certain as possible that none of those included in the test were infected, but it still shows an impressive level of protection from the BCG vaccine in what must have been a highly infected population.

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So DO 30% of badgers in the IAA have bovine TB?

The assertion that 30% of badgers in the area have TB is scientifically dubious. The badgers found dead survey found that 15% of badgers in Pembrokeshire had TB, and WAG appear to rely on another article (Crawshaw, T. R., Griffiths, I. B., & Clifton-Hadley, R.S. 2008, "Comparison of a standard and a detailed postmortem protocol for detecting Mycobacterium bovis in badgers", The Veterinary Record, vol. 163, no. 16, pp. 473-477. ) to double that figure.

However the whole of Pembrokeshire figures are not the finest level of detail we have. The map published (originally from "Selection of IAPA Locations", page 17) by WAG during its consultation on the cull shows the results of the Badger Found Dead Survey and Road Traffic Accident Survey - and you can see that there are far far fewer than 15% infected badgers. For the area marked by the circle, or for the whole page, the figure is nearer 5%. So even accepting the WAG's doubling of the measured figure, we only have a figure of around 10%.

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Would a high level of badger TB favour a cull?

Not necessarily, at least at the kind of levels that are reasonable from what we currently know.

After all, while the WAG documents optimistically states that "there is not expected to be a significant change in the prevalence of bovine TB in badgers following culling" (http://wales.gov.uk/docs/drah/publications/100920tbconsubmissionen.pdf para 117) this is the best case scenario. The experimental evidence is that culling increases the level of bovine TB in badgers, doubling it in the RBCT trials.

Either way, culling clearly cannot eradicate TB entirely as it at best has no effect on the prevalence in badgers. Only vaccination offers a reasonable chance of addressing TB in badgers.

So, bearing in mind that the long term strategy is likely to be vaccination anyway, once the oral vaccine for badgers is licensed, any measure that makes that option less effective is to be discouraged. The higher the level of TB in badgers now, the less we can afford to use a strategy that might risk making it even higher!

To illustrate, if the current level of bovine TB in badgers is 10%, then a cull that risks raising that to 20% is harmful, but not disastrous, for an eventual programme to eliminate TB from badgers using the oral vaccine. If this had a significant benefit for TB in cattle, and no other alternative was available, it might be argued that culling badgers was worthwhile for the short term benefit despite the set back for the long term aim of eradicating bovine TB entirely.

If the current level is 30%, then doubling that to 60% does become a major setback to the long term strategy. If the current level could be as high as 50% , as sometimes claimed, then doubling that to 100% would clearly be disastrous, both for the long term bovine TB strategy and from the humanitarian point of view.

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Won't sick badgers keep spreading the disease?

Badgers in the wild only have a life expectancy of 4-5 years, and the infected animals are naturally somewhat concentrated in the higher age brackets. A study at Woodchester Park found that while badgers who are infected but are not excreting M. Bovis do not have significantly reduced life expectancies, but excretors and super excretors do.

This article shows that 'infected badgers' (in this case arguably meaning 'excretors', given the test used to detect infection) live an average of 360 days after detection - the longest seen was 709 days. So if new infections in the badger population are significantly reduced, the number of infected badgers will drop rapidly as the infected ones die off.

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Isn't culling better proven than vaccination?

It is true that there has been an extensive and very thorough field trial of culling, the RBCT trials, but the conclusion of that trial was that culling "cannot meaningfully contribute to the control of cattle TB in Britain." WAG seem to try to use the trial as proof that culling has been 'tested' while ignoring its conclusion.

Indeed there is some argument that the results of culling would be more uncertain than those of vaccination. Culling produces two effects that are in opposition:

So anything that disturbs the balance of those two effects could radically influence the results of a cull - even, if the perturbation effect were significantly increased, potentially to the extent of producing an overall harmful effect.

The ISG were very clear that their results can only be extrapolated to other culls that are done in exactly the same way as theirs. For example, during the RBCT areas were normally culled in a two week period - cases where the cull took place over longer periods showed dramatically poorer results. It seems unlikely that the much larger IAA can be culled in such a period of time, and if so we could not confidently extrapolate the results of the IAA cull from the RBCT results.

Vaccination, on the other hand, has no competing negative effect. So we can at least predict for certain that it can only have a positive effect on TB in cattle, a statement we cannot make so surely for culling.

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But still, vaccination is unproven?

No - vaccination in general has been extensively proven as a means of controlling and even eradicating disease in wild animals.

This particular vaccine has also been tested both in the lab and in field trials and a practical trial is currently underway near Stroud. The vaccine is shown to work, even in highly infected populations, and to be safe. It does not, for example, exacerbate TB in infected animals if they are vaccinated, as can happen with some vaccines. So there is no sensible scientific argument that vaccinating "might not work."

What we do not have is absolute experimental evidence for the efficacy of the vaccine - how much to would be expected to reduce the incidence of TB in healthy, vaccinated badgers in the field. The field study only used tests on bodily fluid samples, whereas to measure efficacy they would have had to slaughter and post-mortem the badgers, the commonly accepted test for infection. While this result from the field study should not be confused with efficacy, it did show a 74% reduction in vaccinated, healthy badgers later testing positive to the 'StatPak' antibody test. Some of this might have been due to the vaccine reducing the severity of TB in vaccinated animals, not preventing infection entirely, but this would also be very valuable.

Likewise, we don't have experimental evidence for the effect that vaccinating badgers would have on TB in cattle. We do have extensive modelling studies, including some published by WAG.

Given the conclusions drawn in the various field trials of culling and vaccination, and the uncertainty about the extrapolating the effect of culling from these results, experimental evidence is not a strong argument for culling over vaccination.

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Won't vaccination take much longer than culling to work?

This is often claimed, but appears to have no scientific basis. The experimental evidence is that culling takes about three years to show a beneficial effect. Many models, including those published by WAG during the consultation, also suggest vaccination would have the earliest beneficialeffect.

This graph Graph of simulated results of culling and vaccination is taken from Annex 9 (page 15 figure 3(A)) of the evidence submitted to Elin Jones to justify the cull. It has been edited to remove two curves that are irrelevant to this discussion, to make it easier to read. Culling or vaccinating began in year 120.

The results shown are the levels of cattle herd breakdowns predicted in Pembrokeshire if either nothing is done to badgers (green line), badgers are culled (brown line) or vaccinated (blue line). It can be seen, despite the scale, that the vaccination option not only has as rapid an effect as culling, but actually produces better results than culling for the expected duration of the cull.

Computer models are, of course, only as good as their assumptions, but there is no comparable evidence that we have found to support the often-made claim that vaccination will take much longer than culling to take effect.

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