Memorandum submitted by the RSPCA
The RSPCA is not surprised that badger culling
in the reactive treatment areas of the badger culling trials has
been shown to result in an increase in the TB incidence in cattle.
What is perhaps more surprising is that the trial has shown such
a clear result at this stage.
However, dealing with the initial point first,
we would highlight a few examples from the scientific literature
which illustrate why the recent result is not surprising. Assuming
that badgers have some part to play in disease transmission to
cattle, it has long been argued that badger culling might be counterproductive.
For example, Eunice Overend, writing as long ago as 1980, raised
the question as to whether the gassing of badgers (which was then
the control method used) was "as likely to aggravate the
situation by the disruption of social groups and consequent stress
for survivors, as to improve matters by the elimination of infection".
(Badgers and TB—Does gassing spread the disease? Oryx. August
1980. pp 338-340.)
Some of the research undertaken during the 1980's
supported the suggestion that the disturbance from control operations
affected badger organisation and movement. Badger movements were
more frequent in areas where badger densities were lower and the
social groups and territorial boundaries less well defined. In
an area of Gloucestershire where badger clearance had taken place
the increased mobility of recolonising badgers suggested a more
fluid and disorganised social organisation. (Cheeseman, C L et
al (1988). Mammal Review. 18, 51-59.
The concept of perturbation became more widely
discussed and was examined in modelling work undertaken in the
early 90's (eg, White, P C L and Harris, S (1995). Phil Trans
R Soc Lond B 349, 391-413.)
The Krebs review considered the effect of badger
removal on badger dispersal behaviour and concluded that "Small-scale
badger removals, such as those carried out under the interim strategy,
may not substantially reduce contact between cattle and infected
badgers because partial removal of social groups causes disruption
in territorial and dispersal behaviour. Altered territorial behaviour
may increase the risk of transmission to cattle . . . Furthermore,
changes in dispersal behaviour might lead to spread of the disease
amongst the remaining badgers." Bovine Tuberculosis in
Cattle and Badgers. 1997. MAFF. PB 3423.)
Continued work by MAFF biologists illustrated
that ". . . in low-density or perturbed populations where
there is more movement, the risk of transmission of M bovis between
social groups may be even greater. This is of fundamental importance
in the formulation of badger control policy, because a possible
consequence of limited control operations might be an exacerbation
of disease spread." (Rogers, L M et al 1998. Proc
R Soc Lond B 265, 1269-1276.)
The consequences on aspects of badger behaviour
were specifically studied following a typical badger removal operation
at North Nibley in Gloucestershire. Badgers moved more between
social groups at North Nibley than in the other study areas particularly
in the aftermath of the removal operations. The disease dynamics
were thought to be different in disturbed compared to undisturbed
badger populations. (Tuyttens, F A M et al (2000) Journal
of Applied Ecology. 69, 567-580.)
The Independent Scientific Group believed that
the randomised badger culling trial ". . . will allow
us to test theories concerning how social group structure and
perturbation affect the distribution, prevalence and severity
of TB infection." (para 7.5.2. Second Report of the Independent
Scientific Group on Cattle TB 1999)
Thus, given the previous research, the outcome
of interim analysis by the ISG that led to the Ministers decision
to suspend badger culling in the reactive areas is, we believe,
not surprising. It is, however, the first time that the effect
in relation to TB incidence has been quantified.
However, what we did find rather surprising
was, at this stage, the ability of the ISG to produce such a clear
and statistically significant result from the reactive element
of the trial. On 23 June 2003, discussions at the TB Forum included
consideration of a review by the ISG of the implementation of
the reactive strategy. (Document TBF90) From this it was apparent
that implementation of the strategy had faced considerable difficulties.
Various proposals were made to improve procedures. Data accumulated
at that stage (as of May 2003) amounted to 23.4 triplet years
and it was considered that 50 reactive trial years worth of data
would not accrue until 2005. Similarly, there was no indication
at the last meeting of the TB Forum on October 16th that an announcement
was imminent regarding the suspension of the reactive cull. This
seems a little puzzling.
20 November 2003
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