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pathologie@vetmed.fu-berlin.de
Introduction:
Mycobacterium avium subsp. avium (MAA) belongs to the M. avium complex of the non-tuberculous mycobacteria. Primarily affected are birds; they develop lymphoid, gastrointestinal or rapidly progressive disseminated infections. In addition, mammals, especially those with immunocompromising disorders, are susceptible.
Materials and methods:
A 3-year-old British Shorthair cat presented clinically with anaemia, fever and a cardiac murmur. An autoimmune disorder was suspected by the veterinarian and immunosuppressive therapy was initiated. Liver and bone marrow smears revealed abundant intra- and extracellular rod-shaped to filamentous bacteria. Rapid clinical deterioration prompted euthanasia. Necropsy was performed. The smears and diverse tissue samples were subjected to HE stain, PAS reaction and Ziehl–Neelsen stain. Microbiological investigation was initiated.
Results:
Acid-fast stains identified bacteria in the smears to be resistant, excluding Actinomyces spp, and leaving Nocardia spp or Mycobacterium spp as possible aetiological agents. Histopathology revealed granulomatous inflammation of diverse parenchyma with abundant intracellular acid-fast and PAS-positive bacteria, consistent with atypical mycobacteriosis. MAA was identified by culture and PCR in all sampled organs including brain and bone marrow.
Conclusions:
Feline leprosy caused by M. lepraemurium and atypical mycobacterial infections are not uncommon in cats but characterized by dermal, often nodular, “tumour-like” skin lesions. Disseminated infections resembling tuberculosis are extremely rare in feline patients and are more likely caused by M. avium subsp. hominissuis in the context of immunosuppression. Although this also applies for the present case due to respective medication, the clinical and pathological presentation, history and causative agent are noteworthy.