Partial protection against oral challenge with Mycobacterium bovis in ferrets (Mustela furo) following oral vaccination with BCG

SETTING: Ferrets (Mustela: furo) are important wildlife vectors of bovine t uberculosis (TB) in New Zealand. Protective vaccination of ferrets may limi t the potential of transmission to livestock. OBJECTIVE: To determine whether orally-delivered Mycobacterium bovis BCG ca n confer protection against oral challenge with virulent M. bovis. DESIGN: Ten ferrets were vaccinated by feeding measured doses of live BCG, and subsequently challenged with virulent M. bovis via the oral route. Ten non-vaccinated (control) ferrets were similarly challenged. Live body weigh ts and lymphocyte reactivity were monitored longitudinally, and ferrets wer e killed 20 weeks following challenge. Necropsy, histological examination a nd bacterial culture of alimentary tract lymphatic tissues were undertaken. RESULTS: There was a significant reduction in the incidence of gross tuberc ulous lesions among vaccinated ferrets compared to control animals, and few er vaccinated ferrets had histologically-detectable acid-fast organisms in mesenteric lymph node (LN) tissues. There were significantly fewer vaccinat ed ferrets with culture-positive retropharyngeal LNs, and the mean bacteria l burden was significantly lower for retropharyngeal LNs isolated from vacc inated animals than from controls. CONCLUSION: These results demonstrate that oral BCG vaccination of ferrets can confer partial protection against M. bovis, and suggest that systemic i mmune responses may be less important in mediating this degree of protectio n than local immunity.