A new bovine TB control strategy to be piloted in Northern Ireland risks spreading the disease rather than supressing it, scientists warn.
Researchers from the Zoological Society of London (ZSL), Imperial College London and the University of Sheffield predict that culling badgers which test positive for TB could increase the movement of remaining badgers, potentially infecting more cattle with the disease.
Published today in the journal PNAS, their paper shows that small-scale, selective culling may have the same effect on badger behaviour as the Randomised Badger Culling Trial, where the removal of large numbers of animals led to expanded badger ranging.
The Test-Vaccinate/Remove (TVR) pilot will carry out live TB tests on badgers, aiming to vaccinate healthy animals and cull infected ones. However, the test does have its limitations. In a previous study, only 49 per cent of badgers later shown to be infected tested positive in the live test. This means many badgers carrying TB could be missed.
To predict the impact of the TVR pilot on the remaining badgers, the researchers analysed badger movement in 826 territories where small-scale culling took place between 1986 and 1998.
Their results show that removing a small number of badgers from a social group led to increased dispersal and expanded ranging of remaining badgers, more frequent immigration of badgers from outside the group, lower genetic relatedness of individuals within a group, and an elevated prevalence of the bacterium that causes bovine TB.
Prof. Rosie Woodroffe, Senior Research Fellow at ZSL said: "TVR sounds appealing because only infected badgers are killed. Unfortunately our findings suggest that the planned TVR pilot could alter badger behaviour in ways which risk exacerbating the bovine TB problem, rather than controlling it. This is one reason why ZSL is exploring alternative options to reduce transmission between badgers and cattle."
The researchers recommend that if the TVR pilot goes ahead, then intensive monitoring of badger behaviour should be put in place, and stopping rules enforced if significant changes are observed.
Dr Jon Bielby, Research Fellow at ZSL said: "Our research is the first to look at the effects of removing small numbers of badgers from social groups. The results reinforce the need to fully understand the consequences of methods to control the spread of bovine TB before we embark on them. Otherwise we risk complicating what is already a very complex issue."
Editors' Notes
Copies of the embargoed PNAS paper 'Badger responses to small-scale culling may compromise targeted control of bovine tuberculosis' are available via EurekAlert: http://www.eurekalert.org/
ZSL
Founded in 1826, the Zoological Society of London (ZSL) is an international scientific, conservation and educational charity whose mission is to promote and achieve the worldwide conservation of animals and their habitats. Our mission is realised through our groundbreaking science, our active conservation projects in more than 50 countries and our two Zoos, ZSL London Zoo and ZSL Whipsnade Zoo. For more information visit http://www.zsl.org
About Imperial College London
Consistently rated amongst the world's best universities, Imperial College London is a science-based institution with a reputation for excellence in teaching and research that attracts 14,000 students and 6,000 staff of the highest international quality. Innovative research at the College explores the interface between science, medicine, engineering and business, delivering practical solutions that improve quality of life and the environment - underpinned by a dynamic enterprise culture.
Since its foundation in 1907, Imperial's contributions to society have included the discovery of penicillin, the development of holography and the foundations of fibre optics. This commitment to the application of research for the benefit of all continues today, with current focuses including interdisciplinary collaborations to improve global health, tackle climate change, develop sustainable sources of energy and address security challenges.
In 2007, Imperial College London and Imperial College Healthcare NHS Trust formed the UK's first Academic Health Science Centre. This unique partnership aims to improve the quality of life of patients and populations by taking new discoveries and translating them into new therapies as quickly as possible.
The University of Sheffield
With almost 25,000 of the brightest students from around 120 countries, learning alongside over 1,200 of the best academics from across the globe, the University of Sheffield is one of the world's leading universities.
A member of the UK's prestigious Russell Group of leading research-led institutions, Sheffield offers world-class teaching and research excellence across a wide range of disciplines.
Unified by the power of discovery and understanding, staff and students at the university are committed to finding new ways to transform the world we live in.
In 2011 it was named University of the Year in the Times Higher Education Awards and in the last decade has won four Queen's Anniversary Prizes in recognition of the outstanding contribution to the United Kingdom's intellectual, economic, cultural and social life.
Sheffield has five Nobel Prize winners among former staff and students and its alumni go on to hold positions of great responsibility and influence all over the world, making significant contributions in their chosen fields.
Global research partners and clients include Boeing, Rolls-Royce, Unilever, AstraZeneca, Glaxo SmithKline and Siemens, as well as many UK and overseas government agencies and charitable foundations.
Journal
Proceedings of the National Academy of Sciences