The efficacy of five new attenuated mycobacterial strains compared to BCG as a vaccine against experimental challenge with Mycobacterium bovis in brushtail possums (Trichosurus vulpecula)

Abstract

Vaccinating wildlife against bovine tuberculosis (Tb), in countries with wildlife reservoirs of M. bovis, is thought to be the future solution to prevent livestock from getting re-infected. Five newly attenuated strains of mycobacteria have been developed to provide a possibly better vaccine than BCG against M. bovis in brushtail possums in New Zealand. Strain 2 turned out to give a significantly better protectection against experimental infection with M. bovis in three out of nine measurements when being compared to the none-vaccinated control group. Strains 1 and 5 showed two out of nine; strain 3, 4 and BCG showed zero out of nine measurements of protection that were significantly different than the control group. The use of a new scoring system for the analysis of histological slides is evaluated. The scoring of both granuloma characteristics in the liver and acid fast organisms (AFOs) in the lung seems most promising for the use in future microscopical examinations of possums with Tb.