Bovine TB: Chairman's Introduction
1.0.1 It is now over a year since the Independent Scientific Group (ISG) published its first report "Towards a sustainable policy to control TB in cattle". Many challenges have been faced and much has been achieved since then. This report provides an update on progress (up to and including 30 November 1999), sets out the processes we and the Ministry of Agriculture, Fisheries and Food (MAFF) have gone through to develop and implement the programme recommended, and outlines key issues for the future.
1.0.2 From the outset, the ISG, encouraged by Ministers, has seen the logic of taking a holistic view in the search for a sustainable base to underpin future cattle TB control policies. An over-arching objective of our work is to control TB in such a way as to allow the harmonious co-existence of cattle and wildlife, specifically badgers, since Ministers have made clear that the elimination of badgers is not an option for future policy. We recognise the need to understand the epidemiology of TB in cattle and wildlife better, and the programme of research we have recommended is designed to achieve this. There is a widespread misconception that the research strategy of the Group is concerned only with the field trial. Our first report made clear that a combination of research measures was essential if we were to understand more clearly the epidemiology of the disease in all the species implicated and develop sustainable control policies.
1.0.3 The Group has therefore developed a wide-ranging epidemiological investigation into TB in both cattle and wildlife, of which the randomised field trial - a central plank of the Krebs proposals - is just one part. The approach of the ISG has been to identify the major questions that need to be addressed and how answers can best be obtained. Major questions relate to factors influencing the prevalence and persistence of the disease in cattle and wildlife, risk factors contributing to the development of the disease in cattle, transmission routes between and within species, the use of effective diagnostic techniques and the effectiveness and economic value of potential control options.
1.0.4 Given the lack of investigative tools for studying the epidemiology of TB in wildlife, the field trial is currently the only way we can collect much of the essential epidemiological information and relate the underlying pattern of TB infection within the wildlife population to the incidence of TB in cattle. It is also the only way of quantifying the contribution of wildlife to cattle TB and of determining if culling badgers is an effective method of controlling TB in cattle. It is essential to find an effective and acceptable way to control cattle TB in the long term. Failure to complete our work successfully could leave the whole issue in limbo for a further extensive period.
1.0.5 An extensive package of research has been put in place by the Government on our advice. Many of its components are interlinked, and need to be run in parallel with the field trial. In addition to the studies mentioned above, work is ongoing to develop new technologies to improve disease diagnosis in cattle and wildlife and to develop effective vaccines, to track the movement of tubercle bacilli between and within species more accurately and to gain more information on the ecology of wildlife hosts.
1.0.6 An important component of the research is a comprehensive risk assessment. A great deal of attention has been paid to the design and the implementation of a new TB risk factor questionnaire, known as TB99, which, along with other studies, will dovetail with the field trial and enhance the data that are yielded to answer important questions.
1.0.7 Existing TB data, collected in the past primarily to aid on-farm management of incidents, will be evaluated and analysed to provide additional information, particularly on risk factors and the effectiveness of diagnosis.
1.0.8 Factors influencing the persistence of TB in cattle herds and the contribution of cattle-to-cattle transmission to the disease need to be better understood. We are advising in this report that additional work be put in place as a matter of priority to better understand the pathogenesis of TB in cattle. Key questions are: how quickly does the disease develop in cattle, at what stage in the disease process is transmission to other animals likely to occur, how early in the disease process can accurate diagnosis be made, and how effective is the tuberculin skin test in situations of increased disease risk?
1.0.9 It is to be expected that a considerable amount of time and energy has been devoted to the randomised field trial given its scale and complexity. We are committed to the approach which is based on three treatments (proactive culling of badgers, reactive culling after a TB breakdown and no culling at all) applied to discrete areas assembled into “triplets”. Progress with this aspect of our work has been considerable, although not as rapid as initially hoped. Operating procedures have been devised and tested, new staff recruited and trained, and auditors appointed. Six triplets have been identified; work has begun in all of them, though badger culling has so far only been undertaken in two.
1.0.10 It is disappointing and frustrating that circumstances have limited the number of triplets put in place. But, as the Government made clear in its response to the recent Agriculture Select Committee report, there have been unrealistic expectations about the rate at which our programme could be implemented, and we have maintained that it is vital to ensure all elements of the trial and the related research programme are carefully thought-through before initiating any action in the field. It would not have been practically possible to put all ten triplets in place in a short space of time. Nevertheless, we will identify all, and expect to have implemented the majority of, the remaining triplets by the end of 2000.
1.0.11 Difficulties with the course of the trial have undoubtedly served to fuel the fires of the pro- and anti- badger critics and this encourages interference with the work. At one extreme are those who are convinced that badgers are the prime source of TB in cattle and that the only acceptable and effective way to control cattle TB is to eliminate badgers from large tracts of the countryside. At the other are those who believe that the badger is the innocent victim, that culling badgers achieves nothing under any circumstances and should not be countenanced, and that the answers lie in improved cattle disease management and husbandry. Both of these views are based on presumptions coupled with selective interpretation of limited, and often conflicting, available data. We simply do not know enough about the dynamics of the disease at present to eliminate lines of enquiry. The ISG has consciously sought to stand back and take an objective view of the TB problem, and identify, through the best available science, a path to resolving the complex problems posed by bovine TB. If a lasting answer to those problems is the goal - as it must be - the outcome of our work should not be prejudged and our epidemiological investigation, including the trial, must be allowed to run its course without interference. All elements must be pursued; an incomplete picture will benefit no-one.
1.0.12 The ISG and MAFF have taken this message to various organisations and individuals over the last sixteen months, and of course to the Agriculture Select Committee, but it is clear we must extend our efforts in the future. We look forward to working with the Ministry in their continued efforts at improving public understanding of the problem and the Government’s strategy for addressing it. For the year ahead more generally we hope to see more research work initiated, as well as substantial progress in the enrolment of new trial areas. The fruits of some retrospective analyses of existing TB data should become available, and we aim to undertake an initial analysis of the information accumulated through TB99. Outside our immediate sphere we welcome the creation of the new TB Forum to address the continuing rise in TB incidence in cattle, and we will be playing our part in that initiative.
1.0.13 While the ISG is convinced of the need to maintain its independence, and has not been afraid to assert this, we have necessarily worked in close partnership with MAFF across the broad range of our activities. I owe gratitude to Ministers and MAFF senior management for their support and vocal endorsement. The ISG support team has made a major contribution to our work and especially the advisors from the Central Science Laboratory (CSL), the Veterinary Laboratories Agency (VLA) and the Chief Scientist’s Group. The skills and professionalism of the MAFF Wildlife Unit, tasked with translating our designs into the field, continue to impress - their teams do an excellent job in very difficult circumstances. We are grateful to the Veterinary Field Service for piloting and implementing TB99 and to the VLA Investigation Centres for their support and constructive inputs. My continued appreciation goes to members of the ISG who give patiently and generously of their time in pursuit of a difficult goal, remaining committed to the approach that we are taking.
1.0.14 Lastly, a word about the layout of this report. We have moved away from the format used in our first publication towards the one we adopted for our response to the Agriculture Select Committee. We identify the major questions relating to the epidemiology and pathogenesis of TB in cattle and wildlife, and then comment on how these can be best answered. Other issues relating to development of future policy options are highlighted and we move on to describe progress being made, problems that have been encountered and lessons learned. The extensive appendices add to the information provided in the report. It is certainly my hope that the report is accessible and readable, and that it gets across the breadth and depth of our work.
1.0.15 This report and further information about the ISG and MAFF’s TB strategy as a whole can be found on the Ministry’s Website at the following address: www.maff.gov.uk/tb/
John Bourne December 1999
On to Chapter 2 - Understanding the
epidemiology of cattle TB 
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Page published: 5 February 2003