Granulomatous arteritis/aortitis associated with <i>Mycobacterium genavense</i> in a colony of zebra finches ( <i>Taeniopygia guttata</i> )

<i>Mycobacterium genavense</i> is a common cause of mycobacteriosis in passerine birds. In a research colony of zebra finches (<i>Taeniopygia guttata</i>), 8 birds were diagnosed with mycobacteriosis. The finches had granulomatous inflammation of the heart and heart-base, most with medial expansion of the great vessels containing foamy macrophages and acid-fast bacilli. Non-cardiac inflammatory lesions associated with acid-fast bacteria were found in 2 birds, and extracardiac bacteria were often in lower quantities. Pan-mycobacterial <i>in situ</i> hybridization detected periaortic bacteria in one bird with similar cardiac lesions that was negative for bacteria via acid-fast staining. <i>Mycobacterium</i> genus PCR and sequencing of pooled fecal samples confirmed the presence of <i>M. genavense</i> within the colony. Heart and great vessel lesions have not been previously recognized as a site of localized infection in passerines. To facilitate diagnosis of mycobacteriosis in zebra finches, routine necropsies should include microscopic examination of the heart base great vessels.