A controversial badger cull in the south west of England has reignited the controversy surrounding their role in increasing rates of bovine TB infection, with opponents slamming the slaughter as ineffective and inhumane.
While supporters claim the shootings will control rates of infection, wildlife organisations including the RSPCA and The Wildlife Trusts say a cull is unnecessary and are in favour of a policy based on vaccination.
‘The RSPCA supports the use of vaccines and has actively been urging for a policy based on the vaccination of badgers rather than culling them,’ says the RSPCA’s Andy Robbins. ‘There is a vaccine available for badgers now, but it can only be deployed through injection. A vaccine for cattle is not yet commercially available.’
The Wildlife Trusts (TWT) is also calling on the government to ‘push for changes to allow the cattle vaccine to be deployed. Only then will be able to get on top of this disease in an effective way.’
Vaccination of cattle against TB is currently prohibited by EU legislation because it interferes with the standard tuberculin skin test to detect for TB infection. However, small-scale field studies in Ethiopia and Mexico have recently reported protective effects of between 56% and 68% among vaccinated cattle.
A badger Bacillus Calmette-Guerin (BCG) vaccine – an attenuated strain of the bacterium Mycobacterium bovis (rather than M. tuberculosis in the human vaccine) administered by injection – has been licensed since 2010. Twelve local Wildlife Trusts have vaccination programmes in place or are developing them ‘to demonstrate the practicalities of deploying the injectable badger vaccine’ on nature reserves, according to The Wildlife Trusts’ head of living landscape, Paul Wilkinson.
He points to a study published in 2011, which shows that BCG vaccination of free-living badgers reduced the frequency of M. bovis infection as seen in clinical samples by 73.8% (Proc. Roy. Soc. B., doi: 10.1098/rspb.2010.1953). The study followed TB progress in a badger population in Gloucestershire from 2006 to 2009 and involved 179 vaccinated badgers and 89 controls.
Oxford University researchers, writing in an August 2013 review paper (Proc. Roy. Soc. B., doi: 10.1098/rspb.2013.1634), note that ‘vaccination would be expected to reduce the prevalence of M. bovis infection within badger populations over time,’ with annual vaccinations required to reduce the risk of infection from new cubs.
The paper also refers to efforts to develop a more practical oral badger BCG vaccine by Defra’s Animal Health and Veterinary Laboratories Agency (AHVLA), for which the main technical obstacle is ensuring that individual badgers receive a sufficient dose of live BCG to confer immunity.
‘The draft TB eradication strategy that’s just been released by Defra suggests a timeline of 2019 for the first availability of an oral vaccine,’ says TWT’s Wilkinson.
Speaking on BBC News at the start of the cull, UK environment secretary Owen Paterson commented that ‘if we had a workable vaccine we would use it’, but he added this was at least 10 years away.
According to TWT, meanwhile, the current development of a new EU Animal Health Law also provides an opportunity to change the current legislation to allow TB vaccination of cattle alongside an alternative so-called DIVA test to differentiate infected from vaccinated animals.