An aortitis in the squirrel monkey and its effect on atherosclerosis

The systematic examination of aortas in squirrel monkeys during studies of dietary-induced atherosclerosis has revealed an aortitis in 44% of the animals studied. In most instances the damage observed was a periaortitis characterized by plasma cells and lymphocytes with lesser numbers of eosinophils, mast cells, macrophages and histiocytes in the adventitia. The counterposed intima was often infiltrated by a similar cell population. Extensive lesions included focal penetration of the aorta with subsequent fibrosis of the aortic wall. It was found that the degree of induced atherosclerosis was increased when aortitis was present and that attempted regression by dietary manipulation of previously induced atherosclerosis appeared less effective when complicated by aortitis. The possibility exists that the aortitis and the related lesions of myocarditis and interstitial nephritis were associated with parasites found in these monkeys.