Oral infection of ferrets with virulent Mycobacterium bovis or Mycobacterium avium: Susceptibility, pathogenesis and immune response

Ferrets are important wildlife reservoirs of tuberculosis in New Zealand, w here they acquire infection primarily through scavenging infected carrion. In the present study, groups of laboratory-reared ferrets were infected ora lly with 5 x 10(6) colony-forming units of Mycobacterium bovis or Mycobacte rium avium. Body weight and tuberculin-specific immune reactivity were moni tored at intervals (pre-infection, and 4 and 20 weeks post-infection) and a nimals were killed at 20 weeks post-infection for post-mortem, histopatholo gical and bacteriological examinations. Weight loss was significantly great er in M. bovis-infected than in M. avium-infected ferrets. M. bovis, unlike M. avium? sometimes produced gross necrotic lesions in the mesenteric lymp h nudes. M. bovis invariably produced microscopical foci of Mycobacterial i nfection or tissue necrosis typical of tuberculosis? whereas M. avium did s o in only one of nine animals. Mycobacteria were recovered from the lymphat ic tissues of all :II, bovis-infected ferrets but from only five of nine M. avium-infected animals; and the mean bacterial burdens of the lymph nodes of the head and intestinal regions were > 10-fold and >100-fold greater, re spectively, for M. bovis-infected than for M. avium-infected animals. M. bo vis, unlike M. avium, evoked tuberculin-specific peripheral blood lymphocyt e reactivity and serum antibody responses. (C) 2000 Harcourt Publishers Ltd .