Aortic atherosclerosis in exotic avians

Spontaneous arterial disease is documented in 14 exotic avian orders, and contrasted with that previously found in 333 mammals from the Oklahoma City Zoo. Arteriosclerosis, primarily fatty streaks and fibrous plaques, was noted in 65 (90%) of the 72 birds examined. True atheromata with central necrosis and foci of calcification, often containing doubly refractile cystals, were very common, being observed in 24% of the birds, as opposed to 1% of the hoofed mammals, 3% of the nonhuman primates, 10% of the exotic mammals and none of the carnivores or pinnipeds. Medial degeneration was seen in 6 birds, predominantly the large, nonflying types, and was closely allied to intimal disease, as opposed to medial disease in mammals, which is not related to intimal disease. Atheromatous plaques were noted in the penguins, previously thought to have species-resistance to atherosclerosis in spite of elevated serum cholesterol levels. The carnivorous birds exhibited a high incidence of arterial disease with extensive lipid deposition, in marked contrast to the lipid-poor lesions characteristic of the carnivorous mammals. The relatively high blood pressure and serum cholesterol levels of birds are felt to be responsible for the high incidence of atherosclerosis observed. The paucity of mural thrombi in birds may explain the absence of ischemic complications in the face of rather extensive atherosclerosis.