Bovine TB vaccination

Written evidence submitted by the British Veterinary Zoological Society

1. The British Veterinary Zoological Society (BVZS) represents around 450 veterinary surgeons with an interest in exotic animals and indigenous wildlife. Our membership includes specialist wildlife, zoo and exotic veterinary surgeons, but also represents those in small animal practice with an interest in these species.

2. Although BVZS is a division of the British Veterinary Association, BVZS views on bovine tuberculosis (bTB) in cattle and badgers, especially with respect to the targeted cull of badgers, differ significantly from BVA policy. BVZS believes, for reasons based upon strong scientific data, that there is no evidence to support the culling of badgers as part of policy to control bTB in cattle. Other methods of controlling the disease, such as vaccination, must be used and are already available to us. BVZS therefore welcomes this opportunity to provide evidence to the Committee on the vaccination of badgers and cattle in relation to bTB.

Badger vaccination

3. An intramuscular BCG vaccine was licenced for use in badgers in the UK in 2010 following considerable experimental research in the UK and Ireland (Lesellier et al., 2006; Corner et al., 2007; Corner et al., 2008; Lesellier et al., 2008; Lesellier et al., 2009). Vaccination of badgers has been shown to result in significant reduction in the severity of disease, the number of tissues containing acid-fast bacilli, and reduced bacterial excretion (Lesellier et al., 2011). Field studies have shown the vaccine to reduce positive serological results in badgers by 74% (Chambers et al., 2011). Modelling studies have additionally suggested that vaccination of badgers can make a significant contribution to controlling TB in cattle (Wilkinson et al., 2004; Smith et al., 2012). As well as reducing disease in individual animals, BCG vaccination has been shown to have significant positive indirect effects on a population basis, including reducing bTB infection in unvaccinated badger cubs in social groups where only a proportion of the adults have been vaccinated (Carter et al., 2012).

4. Negative comments have been made regarding badger BCG, suggesting for example that it is a poor vaccine because it fails to protect animals that are already infected – in reality very few vaccines offer protection once an individual is infected with a disease and it is unreasonable to expect BCG to perform in this way. Another criticism is that the vaccine does not offer complete protection, but instead reduces severity and excretion of disease. Whilst this is a valid comment, TB is not a simple disease in terms of immunity and developing a completely protective vaccine is unlikely to happen in the near future. The spread of disease, both between badgers and potentially to cattle, is governed by excretion of mycobacteria and a vaccine that reduces this is a powerful tool. Much is also made of the fact that there is no published scientific evidence that vaccinating badgers will have an impact on the disease in cattle. This is indeed the case at present as the very much reduced vaccine field trial is still underway. Extrapolating our knowledge of how the vaccine works to how it might reduce potential transmission of disease between badgers and cattle, would however suggest a significant benefit. The disease in cattle is of course, influenced but many more factors than just the disease in badgers.

5. Badger BCG vaccination has been used in FERA field trials in some areas of England and is currently an important part of bTB control methods in Wales. The vaccine has also been used by many non-government organisations (NGOs) in England and Wales to protect badgers on farmland at the request of farmers and organisations such as the National Trust.

6. Delivery of the injectable vaccine is time and resource consuming. Members of NGOs such as the Badger Trust have ensured that they are trained and equipped to vaccinate badgers, but their efforts are limited and not co-ordinated around the country. A proper system of making badger vaccination easily accessible to farmers is essential, ideally by government. If vaccination is to be left to NGOs then suitable co-ordination and funding is required, whilst at the same time providing these organizations with assurances that badgers they vaccinate will not be culled.

7. It is recognised that there are delivery issues with an injectable vaccine and that an oral baited BCG vaccine would be preferable. An oral lipid matrix vaccine has been shown to be effective with a decrease in the number and severity of gross lesions, lower bacterial load in the lungs, and reduce the number of sites of infection in vaccinated badgers (Corner et al., 2010) and field trials of this vaccine continue in Ireland. There are some delivery issues to overcome with an oral vaccine, ensuring maximum exposure to badgers whilst avoiding ingestion by non-target species, however such vaccines have been deployed successfully to control bTB in possum in New Zealand.

We welcome the Government’s commitment to further invest in this area

Vaccinating cattle

8. BCG can be used as a vaccine in cattle. Its efficacy is much as in badgers and other species, being not wholly protective against infection, but reducing the progression and severity of the disease in those animals that become infected and consequently reducing disease transmission between individuals. It is of course much easier to vaccinate cattle then badgers and this allows for whole populations to be vaccinated, as well as allowing targeted use of the vaccine, for example in young calves where its efficacy is increased (Buddle et al ., 2003). BVZS believes a cattle vaccine should be trialed in the UK as soon as possible.

9. Much is made of the challenges of overcoming EU legislation regarding the vaccinating of cattle with BCG. The evidence that the EU would block vaccination or that vaccination would have significant effects on cattle trade is unclear and further clarification from the EU is necessary. In reality many of the objections to vaccinating cattle come more from within the UK, where the concept of zoning of the country with vaccinated and unvaccinated cattle populations and the perceived impact that this may have on trade makes it unpopular with the farming community. BVZS believes clarification of the EU position would help overcome these fears.

9. A differential test (DIVA test) which allows BCG vaccinated cattle to be distinguished from those with infection is also necessary before BCG vaccination of cattle can take place. The current intra-dermal skin test used in cattle is one of the few types of test where consistent interference is seen when BCG is used. Although this is currently the test most commonly used in cattle, other tests are available which allow for the identification of specific antigens that are present in bTB infected animals but are not found in BCG. In badgers such a commercial test exists in the form of the Brock TB Stat-pak (Chembio Diagnostic Systems, Medford, NY), which allows differentiation between vaccinated and infected badgers. There may of course be practical and cost issues with DIVA tests compared to the intra-dermal skin test in cattle, but these should not be insurmountable. BVZS believes that a DIVA test should be trialed in the UK, alongside BCG vaccination of cattle, as soon as possible.

Summary

We believe that vaccination can play an important part in the control and eradication of TB. It must take place alongside other control measures including the slaughter of cattle found to be infected with TB, improved bio-security, and surveillance at all levels in the farming industry. We do not feel that humane badger culling will play a meaningful nor useful part in the control of this disease. We feel resources should be focused and targeted towards the development of a coordinated vaccination policy and the development of better more cost effective and targeted methods of delivery.

References

Buddle, B.M., Wedlock, D.N., Parlane, N.A., Corner, L.A.L., de Lisle, G.W., Skinner, M.A., 2003. Revaccination of Neonatal Calves with Mycobacterium bovis BCG Reduces the Level of Protection against Bovine Tuberculosis Induced by a Single Vaccination. Infection and immunity, 71, 6411–6419

Carter, S.P., Chambers, M.A., Rushton, S.P., Shirley, M.D.F., Schuchert, P., Pietravalle, S., Murray, A., Rogers, F., Gettinby, G., Smith, G.C., Delahay, R.J., Hewinson, R,G., McDonald, R.A., 2012. BCG Vaccination Reduces Risk of Tuberculosis Infection in Vaccinated Badgers and Unvaccinated Badger Cubs. PLoS ONE 7(12): e49833. doi:10.1371/journal.pone.0049833

Chambers, M.A., Rogers, F., Delahay, R.J., Lesellier, S., Ashford, R., Dalley, D., Gowtage, S., Davé, D., Palmer, S., Brewer, J., Crawshaw, T., Clifton-Hadley, R., Carter, S., Cheeseman, C., Hanks, C., Murray, A., Palphramand, K., Pietravalle, S., Smith, G.C., Tomlinson, A., Walker, N.J., Wilson, G.J., Corner, L.A.L, Rushton, S.P., Shirley, M.D.F, Gettinby, G., McDonald, R.A., Hewinson, R.G., 2011. Bacillus Calmette-Guérin vaccination reduces the severity and progression of tuberculosis in badgers. Proceedings of the Royal Society B: Biological Sciences.

Corner, L.A.L., Costello, E., Lesellier, S., O'Meara, D., Gormley, E., 2008. Vaccination of European badgers (Meles meles) with BCG by the subcutaneous and mucosal routes induces protective immunity against endobronchial challenge with Mycobacterium bovis. Tuberculosis, 88, 601-609.

Corner, L.A.L., Costello, E., O’Mearab, D., Lesellier, S., Aldwell, F.E., Singh, M., Hewinson, R.H., Chambers, M.A., Gormley, E., 2010. Oral vaccination of badgers (Meles meles) with BCG and protective immunity against endobronchial challenge with Mycobacterium bovis Vaccine 28, 6265–6272.

Corner, L.A.L., Costello, E., Lesellier, S., O'Meara, D., Sleeman, D.P., Gormley, E., 2007. Experimental tuberculosis in the European badger (Meles meles) after endobronchial inoculation of Mycobacterium bovis: I. Pathology and bacteriology. Research in Veterinary Science, 83, 53-62.  

Lesellier, S., Corner, L., Costello, E., Lyashchenko, K., Greenwald, R., Esfandiari, J., Singh, M., Hewinson, R.G., Chambers, M., Gormley, E., 2009. Immunological responses and protective immunity in BCG vaccinated badgers following endobronchial infection with Mycobacterium bovis. Vaccine, 27, 402-409.

Lesellier, S., Corner, L., Costello, E., Sleeman, P., Lyashchenko, K., Greenwald, R., Esfandiari, J., Singh, M., Hewinson, R.G., Chambers, M., Gormley, E., 2008. Antigen specific immunological responses of badgers (Meles meles) experimentally infected with Mycobacterium bovis. Veterinary Immunology and Immunopathology, 122, 35-45.  

Lesellier, S., Palmer, S., Dalley, D.J., Davé, D., Johnson, L., Hewinson, R.G., Chambers, M.A., 2006. The safety and immunogenicity of Bacillus Calmette-Guérin (BCG) vaccine in European badgers (Meles meles). Veterinary Immunology and Immunopathology, 112, 24-37.  

Lesellier, S., Palmer, S., Gowtage-Sequiera, S., Ashford, R., Dalley, D., Davé, D., Weyer, U., Salguero, F.J., Nunez, A., Crawshaw, T., Corner, L.A.L., Hewinson, R.G., Chambers, M.A., 2011. Protection of Eurasian badgers (Meles meles) from tuberculosis after intra-muscular vaccination with different doses of BCG. Vaccine, 29, 3782-3790

Smith, G.C., McDonald, R.A., Wilkinson, D., 2012. Comparing Badger (Meles meles) Management Strategies for Reducing Tuberculosis Incidence in Cattle. PLoS ONE 7(6): e39250. doi:10.1371/journal.pone.0039250

Wilkinson, D., Smith, G.C., Delahay, R.J., Cheesman, C.l., 2004. A model of bovine tuberculosis in the badger Meles meles: an evaluation of different vaccination strategies. Journal of Applied Ecology, 41, 492–501

January 2013