Cats are quite resistant to infection with Mycobacterium tuberculosis ; however, they are susceptible to Mycobacterium bovis, Mycobacterium microti, and Mycobacterium avium complex. Lesions in the abdominal organs, such as the mesenteric lymph nodes, are associated with ingestion of contaminated milk or contact with M microti–infected rodents. Infection can rapidly disseminate to other organs, including the lungs and regional lymph nodes. Infected skin or deeper wounds sometimes give rise to tuberculous sinuses. Lesions have a central area of caseous necrosis, usually without calcification.
Tuberculosis symptoms are usually nonspecific, although lymphadenopathy and interstitial pneumonia are common presentations. Tuberculosis should be suspected in cats exposed to potentially infected humans, livestock, or wildlife, and those showing pneumonia, lymphadenopathy, or abscesses nonresponsive to antimicrobial therapy. Diagnosis may be assisted by radiography, echography, demonstration of mycobacteria by Ziehl-Neelsen coloration or PCR on biopsies or cytology specimens, and immunological tests such as lateral flow and IFNγ assays. The tuberculin skin test is unreliable in cats. Treatment can control disease progression but is often not performed, and the animals are euthanized for public health concerns.