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

Mycobacterium genavense is a common cause of mycobacteriosis in passerine birds. In a research colony of zebra finches ( Taeniopygia guttata ), 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 in situ hybridization detected periaortic bacteria in one bird with similar cardiac lesions that was negative for bacteria via acid-fast staining. Mycobacterium genus PCR and sequencing of pooled fecal samples confirmed the presence of M. genavense 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.