By Joseph Bailey, University of Nottingham, UK.
If I mention bovine tuberculosis (bTB), I imagine that a badger, not a cow, would come to mind for many people. British news has recently reported a push for culling these mammals and calls from others for vaccination, with the intention of curbing the spread of bTB. Some famous faces have also engaged in the anti-culling debate (e.g. see ‘Stop the Cull’). There are strong views on both sides because of the damage that bTB can do to cattle herds and farmers’ livelihoods. All parties, of course, want to see a decrease in bTB cases; it is just the preferred means that differ. Here, I outline the debate and move on to discuss how geographical research can help.First, why are badgers getting all of the press? Badgers, along with a number of other mammals, are capable of contracting bTB and spreading it to cattle, the result of which can be devastating because cows that test positive are compulsorily slaughtered. Badgers, perhaps justifiably (they can and do infect cows with bTB), perhaps not (reported infection rates vary but can be very low), are often referred to as a natural ‘reservoir’ of the disease and there is now a strong association between badgers and bTB in cattle. The Government has approved badger culls in England, whilst the Welsh Assembly has favoured a vaccination programme. .
The BBC recently reported on the decision for future culls in England to not be independently monitored as they have been previously. Naturally, this has been heavily criticised and it is disturbing considering the outcome of last year’s pilot culls. However, to many, culling generally seems to not be a sensible or sustainable solution, not least because of the high uncertainty surrounding badger numbers and the associated need for highly costly surveys to decrease this uncertainty and reduce the risk of causing local extinctions, costs which potentially make the whole process financially impracticable (Donnelly & Woodroffe, 2012). Most importantly, such local extinctions would be a tremendous natural loss to an area.
Culls in England were criticised by a Welsh Minister earlier this year who referred to ‘promising’ results from the vaccination efforts in Wales. It has been shown that only a minority (even with varying figures) of badgers actually carry bTB (see The Wildlife Trusts infographic and references therein), meaning that many uninfected, healthy badgers are likely to be killed during a cull. Unlike with vaccinations, culling can also cause badger populations to spread unpredictably (known as perturbation), making control of any infected badgers not killed during the cull more difficult, thus potentially increasing the likelihood of the disease spreading.
Nationally, the Wildlife Trusts are leading the way with badger vaccination efforts and no Wildlife Trust allows culling on its land. Given that badgers live for 3–5 years, it is estimated that herd immunity could be achieved within 5 years (see bottom) as infected animals die over time and the proportion of vaccinated animals increases. How to target vaccination efforts, though? This is where geographers can help.
A recent article in Area (Etherington et al., 2014) recognises the importance of landscape isolation and connectivity, alongside data on badger presence and abundance, in mapping the spatial variation in bTB. Such knowledge is potentially very valuable for bTB management strategies. Indeed, understanding badgers’ local or landscape scale population dynamics and their isolation or connectivity within that broader landscape could allow for more effective vaccine distribution within an area surrounding a farm, for example. Namely, if a population is likely to be connected to certain other populations and a certain farm, it follows that these populations should be vaccinated in parallel. That is of course a simplification of reality, but an enhanced understanding of such dynamics will hopefully be able to contribute to bTB management.
It shouldn’t be forgotten that bTB in badgers represents a small, albeit significant, part of the overall bTB crisis. Overall, it seems to me that targeted vaccination of badger populations in combination with enhanced biosecurity (I have not discussed this here but it is a significant part of the solution; e.g. ‘badger proofing’), is clearly a superior solution to culling when it comes to achieving long-term reductions in bTB. Such an approach also ensures the survival and welfare of the badgers that so many people deeply care about.
(For another Geography Directions blog post on bovine tuberculosis, see ‘Badgers, borderlands and security‘ (by Helen Pallett), which discusses the inherent complexities of disease in nature.)
Donnelly, C. A. & Woodroffe, R. (2012). Epidemiology: Reduce uncertainty in UK badger culling. Nature 485, p. 582.
Etherington, T. R., Trewby, I. D., Wilson, G. J. & McDonald, R. A. (2014). Expert opinion-based relative landscape isolation maps for badgers across England and Wales. Area 46, 50-58.