August 27, 2013

expert reaction to the badger cull beginning in Somerset

The long-proposed badger cull commenced in England, with controlled shootings going ahead in Somerset and more planned in Gloucestershire. 

Professor Christl Donnelly, Professor of Statistical Epidemiology, Imperial College London, said:

“Careful consideration should be given to the role of badger vaccination.  The fact that it does not cure infected badgers does not make it ‘pointless’.  The purpose is to limit the spread to as-yet-uninfected badgers.  We know that, while badger culling decreases the number of badgers in an area, culling increases the proportion of badgers which are infected with the TB bacteria (M. bovis), probably due to disruption of territorial organisation elevating contact rates between badgers.  Also, the increase in prevalence of badger TB is more marked close to the borders of culling areas and in areas lacking geographical barriers to badger migration*. Thus, waiting until after culling to begin badger vaccination will almost certainly make vaccination proportionately less effective among the remaining badger population.”

*Woodroffe R, Donnelly CA, Jenkins HE, Johnston WT, Cox DR, Bourne FJ, Cheeseman CL, Delahay RJ, Clifton-Hadley RS, Gettinby G, Gilks P, Hewinson RG, McInerney JP and Morrison WI. Culling and cattle controls influence tuberculosis risk for badgers. Proceedings of the National Academy of Sciences 103, 14713-14717, 2006.

Prof Lord Krebs, Professor of Zoology at the University of Oxford, said:

“The scientific evidence relating to the impact of badger culling on TB in cattle has recently been reassessed*.  There are no substantial new conclusions.  Long term intensive culling will have a modest effect in reducing TB in cattle, with great uncertainty about the precise magnitude of the effect, but the central estimate is a 16% reduction.

“The two pilots will not yield any useful information.  Defra Ministers have said that the pilots would not enable Defra to “statistically determine either the effectiveness (in terms of badgers removed) or the humaneness of controlled shooting”.  Given this, how can the pilots be a basis for future policy?”

*H.C.J. Godfray, C.A. Donnelly, R.R. Kao, D.W. Macdonald, R.A. McDonald, G. Petrokofsky, J.L.N. Wood, R. Woodroffe, D.B. Young, A.R. McLean (2013), ‘A restatement of the natural science evidence base relevant to the control of bovine tuberculosis in Great Britain’, Proceedings of the Royal Society, Biological Sciences – http://rspb.royalsocietypublishing.org/content/280/1768/20131634.