A new study led by researchers at the University of Saskatchewan offers promising evidence for the use of orally administered live Bacillus Calmette-Guérin (BCG) and heat-inactivated Mycobacterium bovis (HIMB) to protect bison against bovine tuberculosis (BTB). With BTB endemic among wood bison populations within Canada’s Wood Buffalo National Park (WBNP), this research is pivotal as the disease poses significant threats to both wildlife and livestock.
Bovine tuberculosis is caused by M. bovis, which can severely impact bison health and contribute to economic losses within livestock populations. The study highlights how BTB leads to significant lung lesions and ill health, which can jeopardize the long-term existence of this ecologically and culturally important species. Bison are among the last remaining wildlife reservoirs of BTB, and traditional control methods have often faced substantial public resistance, calling for innovative solutions.
Researchers began by aerosol challenging healthy young bison with differing doses of virulent M. bovis, monitoring clinical signs and disease progression. Subsequently, bison received either the live BCG vaccine or heat-inactivated M. bovis through oral administration, providing them with immunogenic challenges similar to what they might encounter naturally.
The results were compelling: both the live BCG and HIMB vaccines contributed to improved health outcomes for vaccinated bison compared to unvaccinated controls. Notably, those treated with BCG fared the best, displaying fewer lung lesions and overall higher survival rates. The scientists observed, "While both BCG and HIMB offered protection against BTB, BCG-treated bison thrived more, presented with fewer lung lesions at necropsy and lower burden of virulent M. bovis than HIMB-treated animals.”
One remarkable aspect of the study was the demonstration of delayed-type hypersensitivity responses to intradermal tuberculin following immunization. Bison receiving HIMB presented almost no hypersensitivity, solidifying the potential utility of this treatment as part of the DIVA (differentiation infected from vaccinated animals) approach for managing BTB.
Given the promising findings related to both vaccines, bison populations previously affected by BTB could greatly benefit from these oral vaccine strategies. BCG, originally developed for human tuberculosis, shows substantial capability not only to protect vulnerable wildlife populations but also to mitigate zoonotic TB risks posed to livestock.
Despite the encouraging outcomes, researchers assert the necessity of large-scale field trials to validate vaccine efficacy within natural bison herds. They stress the importance of developing diagnostic techniques not merely relying on tuberculin-based tests, especially for BCG vaccinated animals as those could yield false positives.
The work done by the scientists emphasizes the interconnectedness of wildlife health, public safety, and thorough ecosystem management practices. These advancements take us one step closer to effective control of BTB among bison, where both animal welfare and ecological integrity can be ensured. This multi-faceted approach to managing BTB highlights the value of innovative strategies to curb this endemic disease and support conservation efforts around wildlife populations.
Going forward, the exploration of alternative diagnostics, such as blood-based tests or antigen specificity, could provide even more viable options for managing BTB effectively. By addressing the challenges faced by bison populations without resorting to drastic measures like depopulation, this research stands as a beacon of hope for wildlife resilience against infectious diseases.