Figure 3.

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^11,12