Unusual lesion morphology and skin test reaction for Mycobacterium avium complex in macaques.

Three rhesus (Macaca mulatta) and one cynomolgus (M. fascicularis) monkey were euthanized because of positive reactions to intradermal tests with mammalian Old Tuberculin (mOT). All the animals had gross or microscopic lesions consisting of unitized macro- or microgranulomas with central necrosis, involving the lung or mesenteric lymph nodes. Small numbers of acid fast organisms were demonstrated in the lesions. Mycobacterium avium complex, serotype 2 was isolated from three of the cases. The cases were unusual because the lesion morphology and mOT hypersensitivity were more typical of mammalian tuberculosis than avian tuberculosis in monkeys.