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DEFRA publishes findings on TB vaccination and culling

by
01 December 2010, at 12:00am

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 in March this year.

The studies were carried out by the Veterinary Laboratories Agency (VLA) and the Food and Environment Research Agency (FERA).

The laboratory studies with captive badgers demonstrated that the vaccination of badgers by injection with BCG significantly reduces the progression, severity and excretion of Mycobacterium bovis infection.

Big reduction

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.

But a number of reservations are listed: (1) the blood test is not an absolute indicator of protection from disease, so the field results cannot give the degree of vaccine efficacy; (2) data from the laboratory and field studies do not lend themselves to giving a definitive figure for BadgerBCG vaccine efficacy; (3) the data do not provide information on the effect of badger vaccination in reducing TB incidence in cattle.

A paper summarising the results of the research has been accepted for publication by the journal Proceedings of the Royal Society B (Biological Sciences) and will be published shortly.

Computer modelling

DEFRA has also published the results of new computer modelling by the 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:

  1. 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.
  2. 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).
  • The results of the research have been published on the DEFRA website and are available at ww2.defra.gov.uk/food- farm/animals/diseases/tb/.