Research into Bovine TB
A significant amount (around £6.9 million in 2010/2011) is spent on a wide-ranging bovine TB research programme with a portfolio comprising projects looking at vaccine development, licensing studies, new diagnostic tests, disease epidemiology, social science, and economic analysis.
- For details of ongoing, or completed, research projects go to http://randd.defra.gov.uk/ and search for eg “bovine tuberculosis”.
Independent advice to Defra on bovine TB-related research is provided by the Bovine TB Science Advisory Body (bTB SAB). This group reports to Defra’s Chief Veterinary Officer and Chief Scientific Adviser through Defra’s Veterinary Research Unit, who act as the secretariat.
The Bovine TB Science Advisory Body (bTB SAB) has three working subgroups focusing on specific areas of Defra’s bTB research portfolio:
- Vaccines Programme Advisory Sub-Group
- Epidemiology & Wildlife Risks Programme Advisory Sub-Group
- Diagnostics Programme Advisory Sub-Group
Badger vaccines research
Defra and its research agencies are among the leaders internationally in developing TB vaccines for badgers, working particularly closely with researchers and Governments in the Republic of Ireland, New Zealand, Spain and the USA. Since 1994 Defra has invested over £16 million on research into badger vaccines.
Injectable badger vaccine
Licensing of the injectable badger vaccine, BadgerBCG, required information on vaccine safety and efficacy, obtained from laboratory and field studies. The laboratory studies with captive badgers demonstrated that vaccination of badgers by injection with BCG significantly reduces the progression, severity and excretion of M. bovis infection.
A key finding of the field study, conducted over four years in a naturally infected population of over 800 wild badgers in Gloucestershire, was that vaccination resulted in a four-fold (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 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.
The reports of these studies are available as follows:
- Safety of BCG vaccine in captive badgers
- Efficacy and safety of BCG vaccine in captive badgers
- Field trial to assess the safety and efficacy of BCG vaccine in wild badgers
Oral badger vaccine
Research and development work is being conducted in collaboration with researchers in the Republic of Ireland and New Zealand. The key areas of work to develop a vaccine and apply for it to be licensed include formulation and bait development, efficacy and safety studies, field deployment studies and preparing and submitting a licensing dossier for assessment by the Veterinary Medicines Directorate.
Cattle vaccines research
By the end of March 2010, Defra had invested over £23 million on the development of cattle vaccines and associated diagnostic tools. As well as carrying out the studies necessary for the licensing of a cattle vaccine, research is continuing on the development and validation of a suitable DIVA test, required to differentiate infected from vaccinated animals, as the lead candidate, BCG, interferes with the tuberculin skin test.
AHVLA is finalising work on the DIVA test and subjecting it to international validation. Changes will be required to EU legislation to allow this test to be used in place of, or alongside the tuberculin skin test to confer OTF status.
Cattle vaccines that do not require a DIVA test, ie do not sensitise cattle to the tuberculin skin test, are a long-term research goal. Work towards this is underway, with the aim of first understanding how reactivity to the skin test relates to the protection conferred by a vaccine.
Work is ongoing to develop practical, sensitive and specific diagnostic tests for badgers, to enable us to assess the geographical scale of the wildlife reservoir and make informed judgements in applying control methods.
Such tests could enable future interventions to be targeted at individual badgers or setts, rather than the wider population, or inform the likely effectiveness of a wildlife vaccination programme in a specific area.
Research is focused on both non-invasive tests to identify infected badgers, including the development of non-invasive blood sampling devices, and tests to identify setts and areas where infected badgers are resident, eg tests to detect M. bovis in environmental (soil, water) samples.
The Randomised Badger Culling Trial (RBCT)
This trial ran from 1998 to 2007 and was overseen by the Independent Scientific Group on Cattle TB (ISG).
The trial took place in thirty 100km2 areas of England, which were grouped into ten sets of three areas (‘triplets’).
In each triplet, one area received repeated culling across all accessible land (proactive culling), one area received culling in response to bovine TB outbreaks in cattle (reactive culling), and the third area received no culling (survey only). Culling operations took place for between four and seven years.
Results showed positive and negative changes in the incidence of bovine TB in cattle as a result of badger culling.
Data collection in these areas is ongoing, and the most recent update shows that a reduction in TB incidence in cattle due to culling persists up to five years after the last cull:
- Analysis of further data (to 2 July 2010) on the impacts on cattle TB incidence of repeated badger culling
National survey of badgers
During December 2011, work began on a two-year national survey of badgers in England and Wales. This is a follow-up to the last national badger survey of Great Britain, which was completed in 1997.