Bovine TB: APPENDIX E - Possible Action outside Trial Areas - Advice to Ministers
BACKGROUND
1.The Group is pleased to respond to the Minister's invitation to take stock and consider whether any steps might be taken outside of the trial areas that might control the rising incidence of TB in cattle.
2.The Group has considered whether the trial should be:
- run as an isolated approach in trial areas alone but combined with a pre emptive culling strategy applied outside those areas (i.e. a combined strategy);
- replaced by pre-emptive culling in areas of high incidence of TB in badgers (i.e. a replacement strategy.)
3.The Group is implementing a strategy based on the conclusions of Krebs. This strategy recognises that while available scientific evidence suggests badgers are involved in cattle TB incidents, it is not presently possible to quantify their involvement or to evaluate the benefit of badger culling. In such circumstances, it is difficult to defend the routine culling of badgers as a disease control policy.
4.The Group has, therefore, advised Ministers to put in place an integrated and open-minded approach to consider what contribution the badger makes, along with other wildlife and cattle, to TB in cattle. The emphasis is on securing a clear understanding of the epidemiology of TB in cattle and other possible wildlife reservoirs in order that future cattle TB control policies can be rationally based.
PRE-EMPTIVE CULLING OUTSIDE TRIAL AREAS
5.In summary, pre-emptive culling outside trial areas would be inconsistent with the objectives and methodology of the trial programme the Group has established. If pre-emptive culling outside currently identified trial areas were to take place in areas of high cattle TB incidence, it would seriously compromise the scientific approach adopted by the Group and effectively nullify the whole trial programme. In order to meet its objectives the trial needs to be located in areas of high TB incidence in cattle; however, the majority of these trial areas have yet to be identified. Any intervention to cull badgers in the potential trial areas would, therefore, render them useless for trial purposes and hence would undermine the trial programme. In addition, it would send a message to farmers inside and outside trial areas that the badger was 'culpable', thereby encouraging many (including those within the "survey only" areas of the trial) to take action into their own hands e.g. by illegally killing badgers. Widespread illegal culling within triplet areas could compromise the integrity of the trial.
6.Furthermore, pre-emptively culling badgers anywhere outside the trial would be inconsistent with the open-mindedness and objectivity that Ministers insisted the Group take in approaching this complex problem, since the philosophy of the trial is that it is currently impossible to assess whether the badger is, or is not, a significant factor in the cattle TB problem. While we recognise the serious dilemma that Government faces as a result of the rising incidence of cattle TB, and that Ministers might wish to adopt the "precautionary principle" and anticipate the possible trial findings on the extent of the badger's contribution, we believe that this would be premature, possibly ineffective and in the longer run damaging. We are unanimous in considering this undesirable.
PRE-EMPTIVE CULLING IN AREAS OF HIGH INCIDENCE OF TB IN BADGERS
7.The Group has considered in depth whether a pre-emptive culling strategy could be applied as an alternative to the trial in areas of high incidence of TB in badgers i.e. a replacement strategy.
8.It is important to appreciate at the outset that there is a major conceptual difference between the replacement strategy approach and that of the Group. Proponents of the replacement strategy make the assumption that badgers are the principal source of infection for cattle, that they contribute considerably to outbreaks of TB in cattle, and that culling badgers is a cost effective means of controlling TB in cattle. This conflicts both with the conclusions of the Krebs report (on which Government policy is based) and with the guiding presumption of the trial programme, namely that the extent to which badgers contribute to TB in cattle remains to be determined. It is possible that the badger removal operations of the past 25 years have been based on a false assumption.
THE REPLACEMENT STRATEGY AS A SCIENTIFIC INVESTIGATION
9.Advocates of the replacement strategy have suggested that it differs little from that of the ISG, although they generally accept that it does not have the same degree of scientific rigour (rigour which, they argue, is unachievable in a field experiment).
10.The Group does not agree that scientific rigour cannot be achieved in a field trial. In addition, it does not accept the assertion that the differences between the replacement strategy and the trial are minor. There are of course some features that are, or could be, common to both approaches. For example:
- accumulation of data on badger density, social group structure, TB prevalence in badgers (but only in areas of assumed high badger TB prevalence where it is suggested pre-emptive culling should be targeted).
- risk analysis could be carried out through the use of an epidemiological questionnaire.
- an ecological impact assessment could be undertaken.
- collateral research (e.g. investigation of TB infection in other wildlife species, validation of observational methods for estimating badger density etc.) could be carried out in pre-emptive cull areas.
- the use of cage-traps only for catching badgers.
- a no-cull period to reduce cubs' deaths in setts.
11.However, as well as the conceptual difference highlighted at paragraph 8 above - concerning the presumed role of the badger - there are other major differences. These relate to the method of selection of triplet areas in the trial and the pre-emptive culling areas proposed as part of the replacement strategy, and the central importance, in the Group's proposals, of the adoption of controls and randomisation. These features are key to the avoidance of misleading conclusions and possible wrong policy choices subsequently.
12.The Group identifies triplets for the trial areas on the basis of specific criteria. These include surface area, a minimum number of holdings and in particular the immediate and past history of cattle TB breakdowns, for which there are reliable, current data. It is anticipated that ten triplets will be enrolled into the trial.
13.By contrast, the replacement strategy proposes that pre-emptive culling should centre on "areas of high badger TB incidence", the assumption being there are "foci" of high and low TB prevalence in badgers. However, it is unclear how such areas are to be identified given the data that are available. Post-mortem data from Road Traffic Accident (RTA) surveys and badger removal operations are the only source of information on prevalence of disease in badgers. These data are limited in both space and time, and are subject to possibly significant bias. Since the RTA survey was suspended in 1990, data on current TB prevalence in badgers are not available. TB in cattle has spread considerably (and unpredictably) in this time, and it is possible that the distribution of TB in badgers has changed in a similar manner. Consequently, there is no rigorous methodology that could be applied to the selection of areas for pre-emptive culling.
14.The proposed replacement strategy raises other fundamental questions that are left unanswered. What TB prevalence would be sufficient to trigger a cull? What prevalence would define the edge of the culling area? Where would the culling stop (in space and time)?
15.The absence in the proposed replacement strategy of comparable "survey-only" (i.e. no culling) control areas eliminates the scientific rigour necessary to quantify the contribution of badgers to cattle TB, or properly to evaluate different culling strategies as future policy options. It is claimed that the "next" identified pre-emptive areas would provide a contemporary control, but these would not be randomised and could not provide a control over time. At best the outcome would be that while a crude, qualitative assessment of the contribution of badgers to TB in cattle might be made, the quantitative effects could not be determined. Hence the proposal amounts essentially to a speculative "clearance strategy", not a structured trial designed to resolve the outstanding questions that have characterised the badger and bovine TB problem for the past 25 years.
WHAT DOES THE KREBS/BOURNE STRATEGY PROVIDE WHICH THE REPLACEMENT STRATEGY DOES NOT?
16.The Krebs/Bourne approach yields a number of benefits, including:
- a scientifically based approach to understand the role of various factors in the development of TB which will provide Government with the information to consider a greater range of policy options for the future.
- an approach with reflects current Government guidelines on basing policy on sound science.
- an objective assessment of the contribution of cattle, badgers and other wildlife to cattle TB incidents with the aim of controlling TB in cattle, not conditioned by the prior assumptions concerning the role of the badger.
- an assessment of reactive culling as a possible future policy option.
- an economic assessment of the costs and benefits of alternative approaches, including badger removal measures.
- collation of scientific data from outside trial areas in later stages of the study.
LOGISTICS AND COST
17.The proposed Krebs/Bourne trial will cover 3,000 sq. km of the South West of England, plus buffer zones, comprising about 10% of the south West (31,210 sq. km in total). Proactive culling will take place in a third of the trial area and reactive culling will also cover a third of the trial area. However with an assumed breakdown rate of less than 30% of the herds in the reactive treatment areas badgers will be culled from not more than 4% of the total South West land mass in the proactive and reactive trial areas.
18.The field programme envisaged for the trial will employ 60 MAFF Wildlife Unit (WLU) staff for the first two and a half years of the trial in order to complete the proactive cull (ten triplets) and concurrently carry out the reactive culls. The final two and a half years will require a lower intensity of culling in the trial areas, but studies outwith the trial areas during this period will involve WLU staff in collecting data from TB breakdown and control farms in addition to trial area incidents.
19.By contrast under the proposed replacement strategy, 12% of the land area of the South West would be pre-emptively culled. A one-off cull with no repeat surveying after the initial pre-trapping survey is outlined in the proposal. It is logistically possible that the goal of completing two proactive culls per year and culling 12% of the South West land mass over a five year period is not unrealistic using the same complement of WLU staff used in the trial. The costs of the proposed replacement strategy fieldwork would not, however, be less than the field trial, and may be more because of the culling intensity over the full five years.
20.Were the replacement strategy proposal to be accepted and implemented concurrently with the field trial, the competition for resources could seriously compromise the field trial and the proposed extension of investigations outside the trial areas. It would also take time for staff to come on stream; the training requirements for surveying, trapping and humanely disposing of badgers are considerable.
21.It is impossible to be precise about the number of badgers that would be killed, but on a straightforward projection based on the area covered, the replacement strategy approach would result in up to three times as many badgers being culled as in the field trial.
CONSIDERATION OF THE REPLACEMENT STRATEGY PROPOSAL AS A POLICY OPTION
22.In view of the acceptance that the replacement strategy proposal would not have scientific rigour, and therefore would not offer the opportunity to resolve the long-standing questions over the nature and quantitative significance of badger involvement in cattle TB, the Group has considered its likely impact simply as an attempted disease control policy. In summary:
- the replacement strategy proposal is based on the twin assumptions that the badger is a major source of infection for cattle, and that the culling of badgers is the most cost effective way of dealing with this. This questions Professor Krebs's conclusions and the Government's decision to implement his recommendations;
- a pre-emptive cull as proposed in the replacement strategy without any attempt to build in scientific rigour would repeat the omissions of the past. It could be designed to provide more high quality data than earlier large-scale culls (e.g. Thornbury) and might also provide an indication whether badgers contribute to TB in cattle. However the central question - what is the quantitative significance of the badger? - would not be answered. As a result of this, the development of future policy options and the economic evaluation of their potential merits would be severely constrained;
- because the pre-emptive cull would be focused on specific areas it is inevitable that large numbers of farmers would feel left out and that their own problem was not being addressed. Even if the assumption on the role of badgers were to be proved correct, the replacement strategy approach is very limited in scale and would likely do little to reduce TB incidence across the wider South West region in either the short term or over the longer term. The resulting demands would be for an even more widespread cull (a reactive strategy?). It is not clear where culling would end - at a point in time or at Land's End? This emphasis could encourage farmers more widely to take the law into their own hands;
- consideration must be given to the influence on cattle TB incidence of repopulation of pre-emptively culled areas. Proponents of the replacement strategy assume that these areas would be repopulated by relatively TB-free badgers, but there is no evidence for this and it must be open to question. A one-off pre-emptive cull would be likely to remove up to 80% of the badger population. One cannot predict how long repopulation would take. It is likely to be shorter than the 10 years or so claimed following the Thornbury cull, where virtually all badgers were eventually removed as a result of an intensive three-year gassing programme;
- there is no evidence to support the claim made for the replacement strategy that fewer badgers would be culled than in the Krebs trial or that Government costs on TB control would be reduced; and
- the message that would be given to conservation groups in the UK and Europe - if unrestricted badger culling was being allowed, at the same time that the Government accepted there was inadequate scientific evidence for involvement of badgers in cattle TB breakdowns - would invite very predictable reactions.
OTHER ISSUES
23.The Group has considered a number of other options including the use of TB 99 outside trial areas, the design of the RTA survey and proposals for cattle free zones and "firebreaks", put to the Agriculture Select Committee, and its views are as follows:
- the new TB 99 questionnaire should be applied nationally as soon as practicable, but its primary benefit in the short term will derive from the detailed data gathered from breakdown farms and controls in the trial areas;
- the new RTA survey, which is an integral part of the trial programme, should proceed on the basis recommended, so that its findings on the distribution, and possibly prevalence of TB in badgers can be validated. It would not be appropriate to extend it beyond the seven counties at this early stage, although the RTA survey's coverage could be regularly reviewed; and
- because of the lack of quantitative data on the contribution of badgers and other wildlife to cattle TB breakdowns, it is not possible to evaluate the benefit of some of the recent proposals relating to cattle free zones and "firebreaks". However, the Group believes there would be merit in exploring the various "cattle-based" options with interested parties, to see if any practical benefits could be gained.
COMPLEMENTING THE TRIAL - FUTURE POLICY OPTIONS
24.It has been clear from the outset that in the short-term neither farmers nor environmentalists were likely to be appeased by the Krebs/Bourne proposals. It must remain a priority for Government to explain to all interested parties that the trial is a carefully thought-through attempt to find sustainable answers to a difficult problem.
25.Planned, targeted meetings with farmers, conservationists and other pressure groups are necessary to get across the objectives of Government policy and the logic of the trial study. Some useful work has already been done. A more general public relations strategy incorporating these meetings, leaflets and publications, and broadcast media could be built up.
26.The precautionary principle could be adopted by the Government in respect of immediate implementation of measures to reduce cattle to cattle transmission, together with consideration of the "cattle" options that have been proposed. This would serve to boost the fourth element of the Government's five point TB research and control strategy:
- protection of public health
- vaccine development
- research into transmission
- strengthening cattle controls
- the field trial
and provide an obvious platform for interested parties (industry groups, environmentalists, veterinarians, scientists, government officials, etc.) to meet and discuss and plan future options. We recommend such a forum be instigated, and would be happy to play an appropriate part in it.
CONCLUSION
27.The Group believes killing badgers outside trial treatment areas should not be sanctioned. It is possible, dependent upon available data, that as the trial continues this policy option could be reconsidered. In the meantime we advocate strengthening cattle controls together with methods for further improving understanding about, and co-operation with, the trial.
April 1999
On to Annex F 
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Page last modified:
12 August 2003
Page published: 5 February 2003