Reports published by DEFRA show how the injectable BCG badger vaccine “significantly reduces the progression, severity and excretion of M. bovis infection” – but computer modelling by FERA claims that a programme of culling plus vaccination would prevent the most cattle herd breakdowns.
Reports published by DEFRA show how the injectable BCG badger vaccine “significantly reduces the progression, severity and excretion of Mycobacterium bovis infection” – but computer modelling by FERA claims that a programme of culling plus vaccination would prevent the most cattle herd breakdowns.
Supporting data behind the successful licensing of the first tuberculosis vaccine for badgers (Badger BCG), which was licensed by the VMD in March, has been published on the DEFRA website. The studies were carried out by the Veterinary Laboratories Agency (VLA) and the Food and Environment Research Agency (FERA).
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% 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 confirm 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 Badger BCG vaccine efficacy – nor do they provide information on the effect of badger vaccination in reducing TB incidence in cattle.
A scientific paper summarising the results of the injectable BCG badger vaccine research has been accepted for publication by the scientific journal Proceedings of the Royal Society B (Biological Sciences) and will be published shortly.
Glyn Hewinson, head of the TB research group at the VLA, and Robbie McDonald, head of the wildlife and emerging diseases programme at FERA, said: “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.”
DEFRA is also publishing the results of new computer modelling by 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.
The results of the modelling were that:
- 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 (while this is not the case for vaccination).
The supporting data for the injectable Badger BCG vaccination and results of FERA’s computer modelling are available at: http://ww2.defra.gov.uk/food-farm/animals/diseases/tb/