Badger cull scheme ‘risks spreading TB’

A pilot scheme to selectively cull badgers testing positive for tuberculosis risks spreading the disease further, scientists have warned.

The new bovine TB control strategy to be piloted in the Banbridge area will carry out live tests on badgers with the aim of vaccinating healthy animals and culling infected ones, as part of efforts to reduce the disease in livestock.

In England the Government has gone ahead with controversial pilots in Gloucestershire and Somerset for large-scale culling, which a long-term “randomised badger culling trial” showed could reduce infection in herds.

But the benefit of culling large numbers of badgers was undermined by the remaining animals moving around more, infecting more cattle with the disease, the trial showed.

New research published in the journal Proceedings of the National Academy of Sciences (PNAS) warns the small-scale, selective culling approach known as test-vaccinate/remove (TVR) being piloted locally could have a similar effect.

The findings are likely to be a blow to those trying to find an alternative to large-scale culling of badgers to tackle TB.

Existing models had predicted that TVR could reduce cattle TB if small-scale culling did not disrupt the remaining badgers into moving around more, but if they did, TB in livestock could increase.

The number of badgers killed in the TVR approach is likely to be low, as there are limits to the numbers of badgers that will be trapped and found to be infected, and only around half (49 per cent) of infected badgers test positive for the disease.

To predict the impact of the TVR pilot in NI, researchers used data from the randomised badger culling trial to analyse badger movement in territories in England where previous small-scale culling had taken place between 1986 and 1998.

The analysis showed that removing a small number of badgers from a social group led to increased dispersal and wider ranging of the remaining animals, researchers from the Zoological Society of London (ZSL), Imperial College London and the University of Sheffield said.

There was also greater influx of badgers from outside the group, individuals were less genetically related within the group and there was a higher prevalence of the bacterium that causes bovine TB.