Oral vaccination of badgers (Meles meles) against tuberculosis: Comparison of the protection generated by BCG vaccine strains Pasteur and Danish

Abstract

Vaccination of badgers by the subcutaneous, mucosal and oral routes with the Pasteur strain of Mycobacterium bovis bacille Calmette-Guérin (BCG) has resulted in significant protection against experimental infection with virulent M. bovis. However, as the BCG Danish strain is the only commercially licensed BCG vaccine for use in humans in the European Union it is the vaccine of choice for delivery to badger populations. As all oral vaccination studies in badgers were previously conducted using the BCG Pasteur strain, this study compared protection in badgers following oral vaccination with the Pasteur and the Danish strains.Groups of badgers were vaccinated orally with 108 colony forming units (CFU) BCG Danish 1331 (n = 7 badgers) or 108 CFU BCG Pasteur 1173P2 (n = 6). Another group (n = 8) served as non-vaccinated controls. At 12 weeks post-vaccination, the animals were challenged by the endobronchial route with 6 × 103 CFU M. bovis, and at 15 weeks post-infection, all of the badgers were euthanased. Vaccination with either BCG strain provided protection against challenge compared with controls. The vaccinated badgers had significantly fewer sites with gross pathology and significantly lower gross pathological severity scores, fewer sites with histological lesions and fewer sites of infection, significantly lower bacterial counts in the thoracic lymph node, and lower bacterial counts in the lungs than the control group. No differences were observed between either of the vaccine groups by any of the pathology and bacteriology measures. The ELISPOT analysis, measuring production of badger interferon – gamma (IFN-γ), was also similar across the vaccinated groups.