Bovine TB: 8 Data Handling
In this section:
8.0.1 A considerable body of data will be generated by the field trial and related research. This chapter sets out what is or will become available, how the data will be analysed and when we recommend they should be released.
8.1 Data availability
8.1.1 Section 7.1.1 outlines the existing TB data that are available. Not all of these are in a user-friendly format, and part of the ongoing research effort is to computerise existing paper records, and render other datasets more accessible.
8.1.2 Data from the field trial are provided to the ISG as soon as they become available, and are regularly updated. As a Group, however, we are deliberately not informed of the incidence of TB in cattle in the trial areas, once selected, in order that our deliberations are not unconsciously influenced by this information.
8.1.3 Of the research projects which have been put in place we will have a direct input into the multivariate analyses of risk factors. These will link with the outcomes of our own analytical work. Similarly, we would expect to direct the analysis of any retrospective husbandry information deriving from the trial areas. With other research work the ISG will play its part in ongoing review procedures, and obviously draw on the results of the various projects when presenting advice to Ministers.
8.2 Analysis
8.2.1 The Group has drawn up a rolling data analysis programme, to take account of existing and future data.
Existing data
8.2.2 Our priorities in this area are to consider:
- cattle testing data (matched, as appropriate, against farm census data) - beginning with a spatial/temporal descriptive analysis of data from the last five, and then ten years;
- BRO data - although badger removal operations, carried out over several decades, were not the subject of scientific controls, it should be possible at least in part to assess their impact on badger populations, the extent of TB infection in badgers, and should also provide a picture of repeat breakdown rates;
- TB49 data (in conjunction with other data sources) - looking for pointers on husbandry and other relevant factors. Much will depend here on the strength of the data the old incident management forms can provide.
Further studies will assess, inter alia, the Woodchester Park data on badger populations, the strain typing database, and the findings from the multifactorial analyses of risk factors.
Trial data
8.2.3 Various elements of the composite trial database will be analysed on an ongoing basis. However, the first comprehensive evaluation will not take place until a sufficiently large sample of data is available (see paragraph 8.2.8 below).
TB99
8.2.4 The use of the TB99 questionnaire for all TB outbreaks since the beginning of 1999 presents, for the first time, an opportunity to establish a comprehensive descriptive database on cattle TB in Great Britain. Initial analyses of the 1999 data by spring 2000 will serve to test the robustness of the data being collected and to help identify where changes to the form could improve its quality and coverage.
8.2.5 The use of both the TB99 case and control forms within field trial areas is crucial. It provides a unique opportunity simultaneously to analyse the data contained therein alongside the information collected during the culling trial on the distribution and the pattern of TB in badgers. In addition, a comparison of TB99 data for case and control farms may identify husbandry and/or farm management practices associated with risk of infection. It will also be possible to undertake further multifactorial analyses by examining TB99 data alongside other datasets (for example, meteorological data) to help determine which factors seem to be associated with TB in cattle.
Working practice
8.2.6 The analytical work will initially be carried out by two research assistants, reporting jointly to the ISG through the Group’s and MAFF’s epidemiological advisors. A composite trial database, including the TB99 epidemiological survey, has been developed by the Veterinary Laboratories Agency, working with the MAFF Wildlife Unit, and building on design work carried out by a contracted spatial epidemiologist during the early part of this year. The research assistants will further develop the database, linking it as appropriate to other datasets.
8.2.7 The ISG has consistently emphasised the importance of blind analysis of the impact of trial strategies on TB incidence in cattle and the absolute need for data confidentiality. The practical considerations of this requirement have been carefully considered. The epidemiologists, supported by their research assistants, will be the only individuals with access to all the relevant data.
8.2.8 After 100 TB incidents have occurred in trial areas (or one year from the end of the second proactive cull) - in other words, November 2000 if not before - a code should be assigned to each of the treatments in the trial areas implemented, and the data presented to the Group. The ISG, directed by its statisticians, will then undertake an initial blind analysis. A similar analysis will be repeated at six-monthly intervals thereafter until the end of the trial.
8.2.9 In the interim, discussions of trial operations data will exclude any cross reference to TB breakdowns in the areas concerned.
8.2.10 The final analysis of the very extensive data that will be available at the end of the trial will, among other aspects, examine the following:
- the overall comparison of the effects of culling on breakdown rates, providing a quantitative assessment of the contribution of the badger to TB in cattle;
- the nature of the differences between and within triplets, and of differences between individual farms within the trial areas including data collected from TB99;
- the significance of prevalence of infection and disease state of badgers.
A synthesis of these and other data, combined with the conclusions from economic and ecological analyses, will form the basis of our advice to Ministers on possible control options.
Timescales
8.2.11 We anticipate that the first analyses of existing TB data (as set out in paragraph 8.2.2 above) should be complete by the close of 2000, and this should help inform the Government’s efforts to strengthen existing TB controls and to advise the farming community on appropriate husbandry practices.
8.2.12 The Group intends that TB99 data arising from the trial areas should be analysed to the same timescale as the trial data (November 2000, if not before). Major revisions of the questionnaire should not be contemplated before then, although MAFF may of course wish to amend the layout of the questionnaire for operational reasons in the light of the interim examination of the 1999 TB data next spring.
8.2.13 Section 4.1 on the design of the trial explains when the trial might deliver final results. The Group understands the enormous pressure from interested parties, and particularly the farming community and conservation bodies, for data from the trial and related studies to be generated, analysed and published as soon as possible. Although it is unlikely, we do not discount the possibility that significant effects from the trial or wider research programme might become apparent before the scheduled end of the trial. However, we emphasise that if future TB control policy is to be put on a sound scientific basis, accurate and comprehensive quantitative data must be gathered and the subsequent analyses carefully carried out. We also emphasise that the integrity of the trial must not be jeopardised at any stage by premature disclosure of data - see paragraph 8.3.5.
Auditing
8.2.14 We have considered the audit of data collected and analysed in the trial, which we referred to in our first report. The ISG intends to carry out its own audit of data (in connection, for example, with the application of TB99) and this will supplement MAFF’s own internal quality checks. However, we plan to return to this area - and the possible need for additional, external audit - during the course of next year.
8.2.15 An analysis of the power of the trial was originally conducted to determine the extent of trial activities necessary to generate sufficient data to allow dependable conclusions to be drawn. The Agriculture Select Committee could find no flaws in this design, but recommended that the original data and accompanying analysis be verified by an independent expert. We accept this recommendation and MAFF has the appointment of this auditor in hand.
8.3 Data release
8.3.1 Our objective throughout has been to be as open as possible about the trial within the constraints imposed by participant confidentiality, safeguarding staff security and protecting the integrity of the trial. This is reflected in the number of meetings and other communications initiatives we have been involved in during the last 18 months.
8.3.2 As far as possible, given the need to protect
personal and commercial information, and resource constraints, we recommend
that MAFF make existing TB data available to the wider research community.
We welcome the publication of monthly
incidence statistics
on the Ministry’s TB Website, and the Government’s more general
efforts to improve understanding about its TB research and control strategy.
Data to be released
8.3.3 The ISG has given very careful consideration to the timing and nature of the release of trial data and operational information. We have concluded that for each triplet the following background and operational details will be routinely released:
- the rough location of trial areas and the treatments allocated to them
- the aggregated history of herd breakdowns across the triplet
- the percentage of the area for which permission for survey and culling was given
- the number of traps used
- the number of badgers and non-target species trapped
- aggregated data on past badger removal operations (including numbers of badgers caught and TB prevalence).
However, in order not to assist those seeking to disrupt the trial and, particularly, for reasons of staff safety, the above information will not normally be released until after completion of initial proactive culling. Those details applying to the first two proactive culls are set out in Appendix B. Hereafter triplet details will be published on MAFF’s TB Website.
8.3.4 Trial data relating to reactive culling and follow-up treatments in proactive areas will be published in the Group’s annual reports. Data from reactive areas will be aggregated to protect landowner privacy.
Risks associated with premature disclosure
8.3.5 It is a fundamental principle of scientific trials that data must not be released prematurely since that could compromise the subsequent integrity of the trials. The Group is concerned that no data should be released from the field trial and related research which could discourage farmers’ willingness to participate in the trial, or encourage either illegal killing of badgers or interference with trial operations. For this reason, we have recommended that a narrow band of data covering the prevalence of TB in badgers caught in the trial, locations of capture, and the number and location of cattle TB breakdowns in trial areas following the selection of trial areas, should not be disclosed. The Group has asserted and reinforced the need for total confidentiality of these data within the Ministry. They will be kept confidential until such time as they can be safely released with a considered analysis by the Group.
Other data
8.3.6 The ISG will consider with MAFF any specific and targeted trial-related data requests not falling into the categories in paragraphs 8.3.2 and 8.3.3 above.
Research projects in trial areas
8.3.7 A number of the research projects commissioned by MAFF on the Group’s advice involve work in trial areas, or with trial-related data or material. Mindful of the risks associated with unguarded or premature release of sensitive details, we have recommended to MAFF that specific confidentiality clauses be inserted in the contracts of the relevant contractors. These oblige the researchers involved to obtain the permission of both MAFF and the ISG before disclosing any such details ahead of the completion of their projects and normal publication of their work. MAFF has accepted this in principle, and we welcome, with our thanks, the understanding and constructive response of the research groups involved.
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Page last modified:
12 August 2003
Page published: 5 February 2003