final report - ARCHIVE: Defra

7 MANAGEMENT TOOLS
7.1 Recommendations of the Krebs Report and subsequent research
7.1.1 The Krebs Report made a number of recommendations for research, for example in areas such as
diagnosis, epidemiology and vaccine development, that were seen as relevant to the development of
new or existing management options in the medium to long-term. Research of this type is considered
in previous sections of our report. Here, we consider recommendations that, while also containing a
research aspect, were directly relevant to the immediate management of bTB in cattle.
7.1.2 Three major recommendations of this type were made, namely that: (i) a controlled trial be carried
out of two culling methods (proactive and reactive culling) to investigate the impact of these on herd
breakdown rates; (ii) more, and transparent, data on herd breakdowns should be collected to assess the
correlates of local variation in risk, taking into account variables such as badger presence, husbandry
practices, climate, landscape, etc.; and (iii) an experiment be carried out involving the manipulation of
husbandry practices, with herd breakdown rate as dependent variable (Krebs et al., 1997).
7.1.3 The first of these recommendations, that a trial of culling methods be undertaken, was fully implemented
in the form of the RBCT (Bourne, 2007). Briefly, the RBCT showed that reactive culling failed to
reduce, and may even have increased, the incidence of bTB in cattle. As a result of this finding, the
reactive culling part of the trial was terminated and reactive culling is no longer regarded as a viable
control option. With respect to proactive culling, the trial showed that while this did reduce cattle bTB
within the culled areas, it increased it in a region, about 2 km wide, immediately surrounding each of
the culled areas (the so-called ‘edge effect’). As a result of this finding, the ISG concluded that proactive
culling was not cost-effective (see also sections 7.2–7.5).
7.1.4 The second of the Krebs Report recommendations, concerning the collection of better data on herd
breakdowns, was implemented in the form of a questionnaire survey. The initial intention was to
collect detailed data on every breakdown that occurred within the RBCT trial areas, and on three
times as many control farms, using a questionnaire called TB99. For logistical reasons, the survey was
subsequently scaled down and a simplified version of the questionnaire (CCS2005) was introduced,
but a substantial amount of data were nevertheless collected. Unfortunately, while the analysis of these
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