A spectrum of immune responses and pathological conditions between certain animal species to experimental Mycobacterium bovis infection.

Guinea-pigs, rabbits, rats, ferrets and hedgehogs were infected with a recent field isolate of Mycobacterium bovis. The cell-mediated and antibody responses were studied up to 8 weeks after infection at which time the animals were killed and pathological, histological and bacteriological examinations were carried out. Guinea-pigs and rabbits produced an intense cell-mediated response and strong tissue reactions around the lesions. This appears, in part, to be responsible for the susceptibility of these animals to M. bovis. The strong cell-mediated response was also related to the small numbers of organisms in the tissues. Ferrets produced very little cell-mediated response and only minor tissue reactions. The lack of any cell-mediate response was related to the large numbers of organisms in the tissues which produced an acute disseminated disease. The antibody response produced by ferrets, rabbits and guinea-pigs was variable within an between the species and could not be related to numbers of organisms in the tissues. In rats and hedgehogs a specific cell-mediated and humoral response was difficult to detect but the growth of the organism was controlled by the host resulting in a persistent subclinical infection with no mortality.