Badger vaccine partial success – But culling still recommended

Badger vaccine and culling

December 2010. Control of bovine tuberculosis (TB) in cattle has proven particularly challenging where reservoirs of infection exist in wildlife populations. In Britain and Ireland, control is hampered by a reservoir of infection in Eurasian badgers.

Badger culling
Badger culling has positive and negative effects on bovine TB in cattle and is difficult, costly and controversial. A new study, published in the Royal Society's scientific journal Proceedings, shows that Bacillus Calmette-Guérin (BCG) vaccination of captive badgers reduced the progression, severity and excretion of Mycobacterium bovis infection after experimental challenge.

Reduced infection levels
In a clinical field study, BCG vaccination of free-living badgers reduced the incidence of positive serological test results by 73.8 per cent. In common with other species, BCG did not appear to prevent infection of badgers subjected to experimental challenge, but did significantly reduce the overall disease burden. BCG vaccination of badgers could comprise an important component of a comprehensive programme of measures to control bovine TB in cattle.

First badger vaccine licensed
Defra has made public supporting data behind the successful licensing of the first tuberculosis vaccine for badgers (Badger BCG), which was licensed by the Veterinary Medicines Directorate. The studies were carried out by the Veterinary Laboratories Agency (VLA) and the Food and Environment Research Agency (Fera).

74% reduction in infection
A key finding of the field study, conducted over four years in a naturally infected population of more than 800 wild badgers in Gloucestershire, was that vaccination resulted in a 74 per cent reduction in the proportion of wild badgers testing positive to the antibody blood test for TB in badgers.

The blood test is not an absolute indicator of protection from disease, so the field results cannot tell us the degree of vaccine efficacy. While the findings indicate a clear effect of vaccination on badger disease, data from the laboratory and field studies do not lend themselves to giving a definitive figure for BadgerBCG vaccine efficacy. Nor do they provide information on the effect of badger vaccination in reducing TB incidence in cattle.


Professor Glyn Hewinson, Head of the TB Research Group at the VLA, and Professor Robbie McDonald, Head of the Wildlife and Emerging Diseases Programme at Fera, said: "VLA and Fera are very proud to have conducted the programme of work on BadgerBCG and that a vaccine is now available for use in the field as one of the tools for tackling bovine TB. In making the data available today, we hope that people will be able to see for themselves the detailed research that went into the development of the vaccine and understand the opportunities and challenges of using vaccination."

Positive result?
Defra has also published the results of new computer modelling by the Food and Environment Research Agency (Fera), which has examined different strategies for controlling TB in badgers, including both culling and vaccination.

The results of the modelling were consistent with the conclusions of the Randomised Badger Culling Trial indicating that there were both positive and negative effects of culling. The modelling shows that badger vaccination could make a positive contribution to disease control in its own right and was consistently positive when used in combination with culling in a ring vaccination strategy. Wildlife Extra questions what measure has been used for ‘positive'? Has this been taken measured from the point of view of farmers or wildlife?

The results of the modelling were:

A combined strategy of vaccination in a ring around a culling area was more successful than the cull-only strategy, which in turn was more successful than the vaccination-only strategy, both in reducing the number of TB infected badgers and cattle herd breakdowns. Ring vaccination partly mitigated the detrimental effects of culling. However, the combined strategy requires about twice as much effort than either single approach done in isolation

Culling of badgers should continue for at least four years to realise a clear benefit. However, low rates of land access for culling, or low culling efficiency, or the early cessation of a culling strategy was likely to lead to an overall increase in cattle herd breakdowns (whilst this is not the case for vaccination).

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