Back to the badgers – the evidence base for bovine Tuberculosis control policies in England and Wales

Wildlife reservoirs for disease make control difficult.

Badgers are just one of many wildlife reservoirs for bovine Tuberculosis around the world.

So the badgers are back in the news, along with cats, of course. The Secretary of State for the Environment, Food and Rural Affairs, Owen Paterson, presented a government statement on strategy for eradication of bovine TB. In brief, his statement acknowledged the severity of the problem facing farmers, the rapid increase in the number of herds affected, the cost of the epidemic as well as the issues associated with any single control measure, none of which present a ‘magic bullet’ solution. As such, multiple measures are being pursued simultaneously, including cattle vaccination trials following EFSA recommendations that are scheduled to start in the near future, badger vaccination already being tested in the field, and programmes to enhance on-farm biosecurity. And of course badger culling.

Mr. Paterson’s statement pointed out that, in countries with a serious wildlife problem, reduction in cattle disease has followed from comprehensive approaches tackling the disease in both the wildlife reservoir and cattle, and indeed, it is likely that such an approach in England and Wales provides the best chance of achieving control. Proper consideration much also be given to the social, cultural and economic factors influencing the epidemic, including both the farming community and the wider public, and with a fuller appreciation of the ecological context of any single control measure, or suite of measures. An intriguing aspect of the problem is the role of legislation governing international trade that represents a considerable cost at the national level, was largely developed in the context of countries seeking eradication when human cases were a greater issue, but now many decades old. How this legislation will stand up in the face of increased evidence of wildlife problems across multiple EU nations including Spain and France and of tuberculosis caused by Mycobacterium caprae in Austria remains to be seen.

Consideration of bovine TB control in England and Wales must consider many inter-related factors

Consideration of bovine TB control in England and Wales must consider many inter-related factors

What makes the control of the problem particularly difficult in England and Wales is the now well accepted evidence that badger culling has the potential to result in both a positive and negative impact on cattle disease. To my knowledge, this makes it considerably different from known wildlife problems in other countries such as New Zealand or for that matter, in the Republic of Ireland, where no such perturbation problem has been observed. While well studied in the context of the randomised badger culling trial or RBCT, whether or not culling results in a positive or negate outcome is likely to be dependent in a complex and as yet poorly understood way on the underlying badger density, existing human interventions (illicit culling, sett disturbance, etc.), the as yet poorly quantified relationship between badger infection prevalence and cattle disease, and the impact of the disease in cattle on the badger population, and possibly other factors. These complex factors mean that any attempt to confidently extrapolate the results of the RBCT at a national scale are at best problematic.

So is there a solution? The statement by Mr. Paterson suggested control of bTB by 2038 would be viewed as success. In order to achieve even such a long term goal, continued investment in not just tackling the problem but understanding it is essential. Policy of course cannot wait for science to come up with definitive answers, but must be sufficiently nimble to respond when scientific evidence changes – the badgers may not have moved the goal posts, but not knowing where those posts are makes scoring that goal even more difficult.

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