Spontaneous arterial disease in exotic animals

An account is given of the pathology and incidence of spontaneous arterial disease occurring in a series of about 2000 vertebrates, the majority of which died in captivity from natural causes. The personal observations are integrated with a fairly detailed review of the literature.

Vascular lesions have been described in fish, amphibians, reptiles, birds and mammals. Particular attention is given in this paper to the comparative pathology of degenerative arterial disease and, more especially, atherosclerosis. Minor degrees of lipid infiltration of the arterial wall are seen commonly in many avian and mammalian orders, but more advanced atheromatous plaques occur frequently only in some avian orders and man. Atheroma has been observed occasionally in sub-human primates and ungulates.

Focal degeneration and calcification of the arterial media constitute the major arterial lesion in ungulates and marsupials; parasitic arteritides are seen principally in carnivores, equines and, possibly, reptiles. Arterial thrombosis in animals is usually secondary to local physical injury or infection; occlusive atherothrombosis is extremely rare in all animals.

A hypothesis is presented on the histogenesis of atherosclerosis as it occurs in animals. It is concluded that the condition is a multifactorial disease. The role of dietary and other factors which may play a part in the pathogenesis of atherosclerosis is discussed. Age is the only factor shown to be fairly directly related to atherosclerosis, but the almost complete absence of lesions in some comparatively old animals emphasizes that atheroma is not an inevitable accompaniment of senescence. The morphological pattern of arterial disease would appear to be similar in free-living and captive animals; and though increasing age and the conditions of captivity may potentiate lesions, it would seem likely that the primary causes of arterial disease are operative in natural, quasi-natural or captive environments.