Bovine tuberculosis vaccine
Bovine tuberculosis has received much attention recently because of debate over how to deal with wild badgers that act as a reservoir for the disease. Trials of badgers culls are due to start shortly but this page explains about the development of vaccines and the importance of animal experiments to develop and test them.
Bovine tuberculosis has a huge economic impact with 29,7 million pounds spent yearly in the UK, as a consequence of the disease. It is the forth most expensive endemic infection to UK agriculture.
Developing the vaccine
In the 1910s, Albert Calmette and Camille Guérin developed a way of culturing the bovine tuberculosis bacillus, Mycobacterium bovis, that made it less virulent. By repeating this over several generations they produced a strain that was attenuated enough that it was unable to cause tuberculosis disease in research animals and therefore suitable for use in a vaccine. This became the Bacillus Calmette-Guerin (BCG) vaccine, developed thanks to animal testing and first given to humans in 1921.While very safe, it is a relatively ineffective vaccine with limited protection against adult forms of the disease. It is now only administered routinely in countries that are highly endemic for TB.
The BCG vaccine has since been tested in brushtail possums, cattle and badgers to determine its ability to prevent infection in some cases, rather than just reducing the severity of symptoms., , These animal experiments helped scientists to realise that BCG can be used to prevent infection rather than being limited to restricting the extent of the disease.
TB vaccines have been developed for cows, however these cause false positives in TB skin tests making it difficult to detect infected animals. It is not possible to vaccinate cows in the field under EU legislation and so research is done on experimentally infected cattle.
Badger vaccination could help reduce the prevalence and severity of bovine TB in a badger population, benefitting both badgers and cattle.
Initial tests to determine the safety of the badgerBCG vaccine required collaboration with researchers in the Republic of Ireland where a facility to house badgers under appropriate biological containment was built. This allowed the determination of a suitable dose of the vaccine.
Tests on badgers deliberately infected with TB were used to show that intramuscular administration was safe and as effective as subcutaneous delivery. This has the advantage of being more easily administered, without requiring the use of anaesthesia. Field trials and experimental infection studies were used to demonstrate that the intramuscular BCG vaccination reduces the progression, severity and excretion of M. bovis infection in badgers.,
Oral vaccines are currently in trials for use in badgers. The formulations used in these trials were developed for possums by researchers in New Zealand and this was all made possible thanks to animal testing.
- LAL Corner et al. (2002) Natural transmission of Mycobacterium bovis infection in captive brushtail possums (Trichosurus vulpecula) New Zealand Veterinary Journal 50(4):154-162 DOI: 10.1080/00480169.2002.36302
- G Ameni et al. (2010) Field Evaluation of the Efficacy of Mycobacterium bovis Bacillus Calmette-Guérin against Bovine Tuberculosis in Neonatal Calves in Ethiopia Clin Vaccine Immunol 17(10):1533-1538 doi: 10.1128/CVI.00222-10
- LAL Corner et al. (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(6):601-609 doi:10.1016/j.tube.2008.03.002
- S Lesellier et al. (2006) The safety and immunogenicity of Bacillus Calmette-Guérin (BCG) vaccine in European badgers (Meles meles) Veterinary Immunology and Immunopathology 112(1–2):24–37 DOI: 10.1016/j.vetimm.2006.03.009
- MA Chambers et al. (2011) Bacillus Calmette-Guérin vaccination reduces the severity and progression of tuberculosis in badgers Proc. R. Soc. B 278(1713):1913-1920 DOI: 10.1098/rspb.2010.1953