842 
ANATOMY AND PATHOLOGY 
ciety. The purpose of the project was to study 
heart disease in zoo animals. 
The material to be presented here was de- 
rived from the study of 405 aortas from 162 
species. Autopsies were consecutive for the 
most part, but all aortas were not suitable for 
study. Complete gross autopsies were done on 
all individuals, with histologic examination of 
most organs and tissues in approximately one- 
half of the cases. Clinical records at the zoo 
were relatively good. Many animals died within 
a few weeks or months after acquisition, how- 
ever, so that correlation of clinical and patho- 
logic data was not always possible. 
Aortas and epicardial coronary arteries from 
large hearts were opened longitudinally, flat- 
tened on cardboard and fixed in 10% formalin. 
After fixation, the vessels were stained with 
Sudan IV in isopropyl alcohol, using a 
modification^^ of the method originally de- 
scribed by Holman et aL^" The extent of inti- 
mal involvement with fatty streaks, fibrous 
plaques and/or complicated lesions was then 
graded independently by two observers and ex- 
pressed as a percentage of the total intimal 
area. Representative blocks of arterial lesions 
were then sectioned on a cryostat and stained 
with Oil Red-O-hematoxylin. The blocks were 
next embedded in paraffin and contiguous histo- 
logic sections were cut and stained with H & E 
and Weigert's elastic stain. Other stains were 
employed as indicated. Portions of this work 
have been reported elsewhere. ^'^■^^ 
RESULTS 
ARTERIOSCLEROSIS 
Aortic Lesions 
Fatty Streaks. Fatty streaks were the most 
common lesions seen, being present in 61 
(51%) of 121 hoofed mammals, 60 (58%) of 
104 nonhuman primates, 7 (13%) of 54 carvi- 
vores, none of 12 pinnipeds, 62 (86%) of 72 
birds, and 11 (26%) of 42 exotic mammals 
(Table I) . Exotic mammals were arbitrarily de- 
fined as those from the orders Insectivora, Ed- 
entata, Rodentia, Marsupialia, Hyracoidea and 
Tubulidentata. Fatty streaks were noted in all 
portions of the aortas, but tended to occur more 
frequently in the thoracic segments. Less than 
5% of the total surface of the aorta was in- 
volved in most of the individuals. Notable ex- 
ceptions were a three year old male chimpanzee 
(Pan troglodytes) with 20%, a squirrel monkey 
(Saimiri sciureus) with 40%, a domestic turkey 
with 80% , a common duck with 50%, and 2 os- 
triches (Struthio camelus) with 60% and 65%, 
respectively (Tables III-VII). Microscopically, 
these lesions consisted of focal deposits of Oil 
Red 0 positive material within a normal or 
slightly thickened intima. Intimal thickening, 
when present, was comprised primarily of 
smooth muscle cells. The lipid droplets were 
usually small and evenly dispersed, although 
typical foam cells were seen occasionally, 
usually in birds or non-human primates. Many 
of the finely dispersed lipid droplets appeared to 
be extracellularly located, although this deter- 
mination was not always easily made because of 
suboptimal preservation of tissues. The lipid 
droplets tended to cluster along the intimal sur- 
face of the internal elastic membrane in the ab- 
dominal aorta, while in the thoracic aorta they 
often extended into the inner media (Figures 1 
and 2). 
Table 1. — Prevalence of Aortic Lesions in Mammals 
and Birds 
Number of Individuals 
Athero- 
With Fatty Fibrous matous 
Species Group 
Total Lesions Steaks Plaques 
Plaques 
Other* 
Hoofed mammals 
121 
82 
61 
57 
1 
20 
Non-human primates 
104 
63 
60 
19 
2 
0 
Carnivores 
54 
19 
7 
19 
0 
6 
Pinnipeds 
12 
11 
0 
11 
0 
0 
Birds 
72 
65 
62 
42 
17 
6 
Exotic mammals 
42 
16 
11 
8 
4 
3 
TOTALS 
405 
256 
201 
156 
24 
35 
* Medial degenerative and parasitic lesions 
Table II. — Prevalence of Coronary Artery Lesions in 
Large Mammals and Birds 
Number of Individuals 
Athero- 
Species Group 
Total 
With 
Lesions 
Fatty 
Steaks 
Fibrous 
Plaques 
matous 
plaques 
Hoofed mammals 
38 
12 
2 
12 
0 
Non-human primates 
17 
5 
3 
3 
0 
Carnivores 
10 
2 
1 
1 
0 
Pinnipeds 
8 
0 
0 
0 
0 
Birds 
7 
4 
4 
3 
0 
Exotic mammals 
5 
3 
2 
2 
0 
TOTALS 
85 
26 
12 
21 
0 
