Cardiovascular disease in free living wild animals with particular reference to the African elephant (Loxodonta africana)

Abstract

A field survey to investigate the ecology of cardio-vascular disease in free living wild animals is described. Its aim was i) to assess the susceptibility of such animals to arteriosclerosis. and particularly to athero-sclerosis ii) to examine in greater detail the ecology of oardiovascular disease in a single, naturally-susceptible species in relation to dietary change and stress in naturally occurring situations. A total of 201 specimens, representing species of mammals and 25 of birds, was examined: 37 species of mammals had uncomplicated lipid deposits in the arterial intima, thought to represent a normal physiological occurrence; 13 had atheroma-like lesions of the intima; 20 species of birds shoved positive lipidosis. These findings. compared with those reported in taxonomioally equivalent groups of captive animals, are discussed. The African elephant was selected for special study. The eoology of its cardiovascular disease patterns was studied in three different habitat types: one natural (the 'control'). and two degenerate ('stressed'). Athero-sclerosis and medial sclerosis were found not to occur in the 'natural' habitat type, but to be directly correlated with habitat degeneration in the other two 'stressed ranges, where 'stress' factors included excessive exposure to sunlight, dietary changes, frustration of the migrator/ habit, disrupted calving patterns9 and over-population neither disease was found to be directly related to age, and each had a distinct intra-arterial development patterns the aetiology of each is therefore thought to be basically independent, although in advanced cases interaction may occur. Incidental results of the survey includes i) observations on the importance of relating the functional anatomy of the arterial supportive thickenings at ostia, bifurcation and regions of mechanical strain to the normal intra-aortic distribution of uncomplicated intimal lipid deposits; ii) observations on a valve-like structure in the aorta of the klipspringer; and iii) the formulation of a new field technique for assessing relative age in the African elephant.