Sir

In your Editorial 'In for the cull' (Nature 450, 1; doi:10.1038/450001b 2007), you implied that my assessment of the scientific evidence relating to bovine tuberculosis (TB) in cattle and badgers was influenced by political considerations. This attack on my integrity as the government's chief scientific adviser has no foundation whatsoever. The editorial staff of a journal surely understand fully the importance of scientific challenge and debate, as distinct from personal attacks. Yet your Editorial does not address the science.

As you point out, the scientific content of the report on cattle from the Independent Scientific Group (ISG), under the chairmanship of John Bourne, has been published in the scientific literature and hence peer-reviewed, but the conclusions reached by Bourne and his colleagues in the report have not.

My role is to provide independent scientific challenge and advice on important issues, such as this, in which the science is critical. To do my assessment, I assembled a team of independent, well-respected experts who brought international expertise in the necessary disciplines, particularly badger ecology, epidemiology, immunology and bovine TB. I had no idea what conclusions they would reach.

Although the scientific conclusions produced by my experts differ from the main conclusion of the ISG report, they nonetheless follow directly from the ISG's data, which clearly show that carrying out badger removal over a large area and a sustained period of time, together with cattle removal and other controls, would deliver an overall reduction in TB incidence in cattle herds. This is the only effective course of action until efficacious vaccines become available.

Bovine TB in cattle is the most serious endemic animal disease in the United Kingdom: the ISG reports a doubling of herd breakdown every 4.5 years in the high-incidence area. These data suggest that, in the randomized badger-culling trial, badgers could account for up to 40% of new confirmed incidents of bovine TB in cattle.

On the basis of the scientific evidence, I do not believe that we can control TB in cattle — and badgers — without removing the sources of infection in both species. Other countries have been unable to control TB in cattle without addressing the wildlife reservoir (N. E. Tweddle and P. Livingstone Vet. Microbiol. 40, 23–39; 1994).

I utterly reject any suggestion that I was — or could have been — influenced in my science advice by farmers, policy-makers or politicians. My mantra of openness, honesty and transparency continues unabated.