Chapter 11 : Tuberculosis in Wild and Domestic Mammals

Abstract:

Different animal species vary in their susceptibilities to infection by the different types of virulent tubercle bacilli: Mycobacterium tuberculosis, M. africanum, M. bovis, and M. avium. Liquefication promotes extracellular multiplication of tubercle bacilli to tremendous numbers, and cavity formation allows these bacilli to spread through the air passages to other parts of the lung and to other people. When pasteurization was adopted, there was usually a concomitant decrease in tuberculosis in children. Tubercle bacilli that are inhaled usually lodge in alveolar spaces, where they are ingested by alveolar macrophages. When the organism multiplies within the phagocyte, the host cell may die, resulting in the development of a microscopic tubercle. Wild mammals found to have tuberculous lesions at necropsy after natural death are usually without prior suspicion of tuberculosis. Tuberculous lesions from camelines, cervines, and wild bovines closely resemble those of domestic bovines. In nonhuman primates, M. bovis, M. africanum, and M. tuberculosis can produce extensive disease involving the parenchyma of the lung as well as extrapulmonary tissues. Recently, there has been increased interest in the isolation of M. avium complex serovars 1, 4, and 8 from patients with AIDS and from nonimmunocompromised patients. Some of the same serovars have been isolated from domestic and wild animals. Although M. avium has been isolated from environmental specimens (i.e., soil and water), no definitive information on a common source(s) of these bacteria for animals and humans is available.