PMC8044568_01
The 7-year-old neutered male Siamese cat, which has brought in a freshly hunted mouse to eat at its feeding station
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It was an indoor/outdoor cat and an avid hunter (Figure 1), with no travel history outside of Scotland.
Dorsoventral (a) and right lateral thoracic (b) radiographs of the patient, showing a diffuse, interstitial-alveolar pattern, most marked on the caudal lung lobes
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Thoracic radiographs (Figure 2) revealed a diffuse, interstitial-alveolar pattern, most marked on the caudal lung lobes.
Interferon gamma release assay (IGRA) results. The response to bovine purified protein derivative (PPDB) indicates that the cat had a significant response to Mycobacterium tuberculosis complex (MTBC) bacteria; the response to avian purified protein derivative (PPDA) indicates that the cat had a weak immune response to members of the Mycobacterium avium complex (or this could be cross-reactivity with MTBC). There was no response, however, to ESAT6/CFT10 peptides, which are present in pathogenic MTBC bacteria, including Mycobacterium bovis and M tuberculosis. Hence, these IGRA results are compatible with infection with a less pathogenic member of the MTBC, most likely Mycobacterium microti in the UK. While M bovis infection can on occasion give this picture, the cat had never been outside of Scotland, which is officially M bovis free
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The interferon gamma release assay (IGRA) was performed, and the results were compatible with infection by the less pathogenic member of the Mycobacterium tuberculosis complex (MTBC); that is, Mycobacterium microti ('the vole bacillus') (Figure 3).
Timeline of the patient's mycobacterial infections. The stars indicate when the presumptive Mycoplasma felis pneumonia episodes occurred. m = months; y = years
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The patient remained asymptomatic for 1 year but was infected with tuberculous pneumonia five more times - a total of six episodes over one decade (Figure 4).