Zoological Pathology Program, College of Veterinary Medicine, University of Illinois, Maywood, IL, USA
Avian mycobacteriosis is an important cause of morbidity and mortality in captive exotic, wild and domestic birds and can affect numerous organ systems. Avian mycobacteriosis has rarely been reported to cause granulomatous arteritis or to affect the myocardium.2,3
In a retrospective study of birds with mycobacteriosis, 14 individuals with vascular mycobacterial infection were identified. Thirteen species were affected, all were adults, and no sex predilection was noted. Disseminated mycobacteriosis was noted in 9 of 14 birds; however, in 5 birds, histologic evidence of mycobacteriosis was only present in the vessels. Vascular lesions were categorized according to the severity of mononuclear cell infiltrate and degree of architectural distortion.
Affected vessels were predominantly the aorta, brachycephalic trunk, coronary arteries and pulmonary trunk. Vascular lesions included mild to extensive accumulations of macrophages, lymphocytes, plasma cells and rare heterophils with variable distortion of vascular architecture. Intralesional acid-fast positive bacilli were generally abundant. Vascular changes were considered mild in four cases, moderate in seven and severe in three. Associated arteriosclerotic and/or atherosclerotic lesions were noted in six cases.
Granulomatous arteritis is an uncommon lesion. An immune-mediated response to mycobacterial antigens is implicated in the human syndrome Takayasu’s arteritis.1 A similar mechanism has been suggested in some cases of human atherosclerosis.4 Interestingly, the distribution of granulomatous inflammation in Takayasu’s arteritis is similar to that noted in these birds. The pathogenesis of these lesions may also be similar; however, intralesional acid-fast bacilli have not been documented in either human disease.
The authors would like to thank the veterinarians and staff of the Lincoln Park Zoo, Brookfield Zoo and Fort Wayne Children’s Zoo as well as the histology laboratory at the Veterinary Diagnostic Laboratory, College of Veterinary Medicine, University of Illinois at Urbana-Champaign for their assistance in this project.
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2. Gelis S, Gill JH, Oldfield T, Jaensch SM, Raidall SR. Mycobacteriosis in gang gang cockatoos (Callocephalon fimbriatum). Vet Clin North Am Exot Anim Pract. 2006;Sep;9(3):487–494.
3. Morton L, Ehrhart EJ, Briggs MJ, Bussan DA, Murnane RD. Granulomatous aortitis and cardiopulmonary arteritis in fairy bluebirds (Irena puella) with mycobacteriosis. Proc Am Assoc Zoo Vet Annu Meet. 1997: 272–273.
4. Rota S, Rota S. Mycobacterium tuberculosis complex in atherosclerosis. Acta Med Okayama. 2005;Vol. 59(6):247–251.