Bovine TB: 12 Summary of the Group's Approach
12.0.1 This report details the programme we have put in place over the last 16 months and explains the philosophy we have adopted. Set out below is a summary of our approach, which we intend to use as both the platform and framework for our future annual reports.
The ISG’s role
12.0.2 The Independent Scientific Group on cattle TB was set up following the acceptance by Ministers of the recommendations contained in the Krebs Report (1997). From this it was clear that the problem of TB in cattle was extremely complex, still poorly understood and that previous policies to control the disease had been inadequate. It recognised that substantial further work was necessary if an informative framework was to be established that would be adequate to underpin an effective policy to control the disease in the future.
12.0.3 The role of the ISG is to provide the scientific base for such a policy. From the outset we have adopted a holistic approach, recognising that sustainable control policies could only be achieved through a better understanding of the epidemiology of TB in cattle and wildlife reservoirs. Implicit in our approach is the recognition that the widespread elimination of badgers from large tracts of the countryside would not be politically or socially acceptable, hence we have sought to explore a much wider consideration of the problem and its possible solution(s).
Epidemiology and pathogenesis
12.0.4 We considered at length the TB problem and the approaches that might be taken at some length and put forward initial proposals, which were approved by Ministers in August 1998. Since then we have, with MAFF, put in place a major research programme on the epidemiology and pathogenesis of the disease. This is designed to advance our understanding of the determinants and dynamics of its persistence and its transmission between and within animal populations, and to explore explicitly the link between TB in badgers and the occurrence of TB breakdowns in cattle herds. Our working approach is built around identifying the major epidemiological questions that needed to be answered and then considering how answers can best be found.
TB diagnosis
12.0.5 The cornerstone of an epidemiological study is accumulation of accurate data on the prevalence and distribution of infection and appropriate analysis and interpretation of the data. But above all there is a need for accurate and sensitive disease diagnosis. There is currently no reliable TB diagnostic test, or range of tests, that can be used in live wildlife. A reliable diagnosis can only be made by post mortem examination and bacteriological culture of body tissues. Thus, regrettably, accurate data on TB prevalence in wildlife - essential to answer critical questions on the maintenance of TB in wildlife and its potential for transmission to cattle - can only be obtained by killing samples of wildlife populations, including badgers.
12.0.6 The accurate diagnosis of TB in cattle is also essential if we are to understand the epidemiology of the disease and put in place effective controls. Current methods of diagnosing TB in cattle have been highly effective in controlling the disease in many countries and in parts of Great Britain. However, given the increased risk of infection in those areas of Great Britain where TB has remained a problem there is a need to question whether cattle TB control in this situation is constrained by limitations in current diagnostic procedures, and to consider the impact this may be having on persistence of the disease and cattle to cattle transmission. A clearer understanding of the dynamics of the disease in cattle and how this relates to and influences diagnosis and disease transmission and prevalence is essential. There is a need for greater effort in this area.
12.0.7 The comprehensive package of research now in place includes therefore, as a crucial component, the use of modern technologies to develop new and improved diagnostic tests for cattle and wildlife. These techniques are also being used to develop molecular tools to discriminate more clearly between the different TB strains, to track more accurately the precise movement of TB organisms between and within species, to understand genetic typing of badger populations and to develop effective vaccines.
Risk factors
12.0.8 A major component of our research initiative is the implementation of a detailed on farm epidemiological survey, collecting information using a carefully designed questionnaire (TB99). This questionnaire is to be administered to all farms experiencing TB breakdowns and, for comparison within trial areas to comparable nearby farms in which no infection has recently been detected. This study is designed to evaluate risk factors which may predispose herds to infection and includes questions relating to herd characteristics, husbandry, land use, and exposure to external and internal sources of infection. The questionnaire has been devised and piloted, staff have been trained in its use and it is currently being applied to breakdown farms within and outside of the trial areas. The questionnaire is comprehensive and demands a high degree of involvement from farmers, which we have consistently received, and for which we are most grateful. We are conscious of criticisms that it is too detailed (though some by contrast believe it could usefully be even more detailed). However, we considered the information needs extremely carefully and recognise that, in the current poor state of understanding of the epidemiology of TB, there is no escape from the need to assemble a database from farms that will allow full analysis of the possible risk factors and characteristics which may explain the occurrence of herd breakdowns, together with other appropriate datasets (including geographical and climatic features). We plan to use the data collected and experience gained in the implementation of TB99 thus far to review its design next year.
The field trial
12.0.9 The randomised field trial is but one part (albeit important) of our holistic approach. It is also the most contentious. There are major epidemiological questions relating to the role of the badger in cattle TB that must be answered, and policy options to be explored if we are to develop a sustainable control policy. These can only be addressed if we have the information to be derived from the trial. Past policies on badger control have not provided quantitative information on the role of the badger in the continued high incidence of herd breakdowns in the “hot-spot” regions. Also it has left open the question whether selective badger culling, improves, worsens or has no effect on the situation. Only by carrying out the randomised field trial in well defined areas can we answer these questions once and for all.
12.0.10 As well as demanding rigorous operational procedures we continue to place great weight on welfare issues in the conduct of the field trial. Culling operations are carried out by specially trained Government personnel and use cage traps only and these are widely considered as a humane form of capture. Standard operating procedures for field work are clearly defined and constantly reviewed and subjected to internal and external audit in order to assure that the highest standards of welfare are met.
Data analysis
12.0.11 Both the randomised field trials and the TB99 investigation will have to be implemented for a number of years before they can generate sufficient information to allow us to offer dependable advice for farmers and Ministers. In an attempt to provide some advice more rapidly we have initiated a full evaluation and in depth analysis of existing data held by MAFF and its agencies.
Interim measures
12.0.12 Realistic and effective proposals, particularly for the short term, for the better management of cattle TB may come from organisations and individuals from outside the ISG and MAFF. We have consistently taken the opportunity to consult widely, and we welcome the creation of the new "TB Forum" to solicit constructive input from interest groups and stake holders. We also welcomed the Agriculture Select Committee’s review of TB control policy and were reassured by their firm support for our activities contained in its report of April 1999.
12.0.13 We are aware that cattle TB incidence continues to rise especially in the south west but also with the emergence of new areas, and this creates a pressure for us to provide answers as quickly as possible. Extreme factions who see badgers as either the villains of the piece or innocent victims have heightened emotions and encouraged increased resistance to the work we are doing. If a lasting answer to the TB problem is the goal - as it must be - the outcome of our work must not be prejudged and our epidemiological investigation, including the randomised field trial, must be allowed to run its course without interference. All elements of the programme, many of which are interlinked, must be run in parallel and to completion. This programme has been carefully planned as a comprehensive and integrated approach to the problem and any lessening or diversion of the effort will result only in an incomplete picture which will benefit no-one in the longer term.
Evaluating progress
12.0.14 Given the scale and complexity of the programme of research that we have proposed some problems in implementation are perhaps inevitable. However, the Road Traffic Accident survey is the only element of the programme we have recommended on which almost no progress has been made so far. This is disappointing since the survey is necessary to yield valuable information. Of greater concern is the delay in getting all the field work in place. Slippage in the programme has allowed only two proactive culls to be completed to date. We accept that it would not have been logistically possible to put all the triplets in place in a short space of time but illegal interference with the field work causes further unwarranted delay, practical concern and frustration in pursuit of the study’s objectives. Nevertheless, by the end of 2000 we will expect all of the planned triplets to have been enrolled and the majority of these to have been proactively culled.
12.0.15 We will continue to monitor the progress of the programme of work now in place and advise on the commissioning of other work as opportunity or need arises. During the next few months we shall finalise triplet selection, and by this time next year, would expect to be in a position to carry out an initial analysis of data.
On to Appendix
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Page last modified:
12 August 2003
Page published: 5 February 2003