SIGNIFICANCE OF SIMIAN VIRUSES 
S. S. Kalter' 
In the pursuit of developing better systems for the 
study of human disease, investigators have gradually 
worked their way up the phylogenetic scale to the cur- 
rent widespread use of monkeys and apes. Approxi- 
mately 100,000 nonhuman primates are imported an- 
nually into the United States with an equal number, 
or more, used elsewhere in the world as laboratory 
animals. Their importation and usage has not been 
without problems. Some of these have been overt and 
others have been at a level not easily recognized nor 
detected except in retrospect or by means of special 
efforts. Most important is the realization that many 
individuals do not recognize or perhaps accept the fact 
that these animals are biologic entities and thus have 
a potential danger by virtue of the "normal" flora and 
fauna, especially viral. Precise information as to what 
. constitutes the normal viral flora of simians is still not 
known. Most available data are derived from captive 
animals and only limited information is available on 
the various species as they exist in nature. Approxi- 
mately 20-30 species of simians, broadly separated into 
Old and New World monkeys and apes, are now in use 
in the laboratory and these vary considerably in their 
viral content as well as their susceptibilities to viruses 
of animal origin. These animals have been responsible 
for introducing such virus diseases as herpes B (Herpes- 
virus simiae), Marburg and hepatitis, into laboratory 
personnel. In the field, contact with simians has resulted 
in the transmission of such diseases as yellow fever and 
Kyasanur forest to humans. Of equal importance is the 
transmission of a number of simian viruses, at times 
with numerous fatalities, from one monkey species to 
another: Yaba and Yaba-like, simian hemorrhagic 
disease, a number of Herpesviruses, especially H. 
saimiri, and so on. Lastly is the exchange of human and 
simian viruses between all the diff'erent primate species 
that are only detected by serologic changes. The extent 
of pathogenesis associated with this last point is 
practically completely unknown. Unquestionably all of 
these eff^ects have a certain influence and significance 
\ on the health of man and simians, experimental eco- 
nomics, as well as on the interpretation and outcome of 
the final experiment. This significance will be discussed. 
♦Division of Microbiology and Infectious Diseases Southwest 
Foundation for Research and Education San Antonio, Texas 78284. 
INTRODUCTION** 
In searching for animal models to be utilized 
for the study of human disease, an increasing 
number of investigators have turned to the non- 
human primate as an attempt to close the phylo- 
genetic gap which exists when other animal 
systems are employed. However, in so doing one 
must be aware of the existence of certain prob- 
lems and the possible relationship these prob- 
lems may present in the final interpretation of 
results. One must also be concerned with the 
very pragmatic aspect of the health and well- 
being of the human and animal populations. It 
is to these considerations that we address our- 
selves at this time. 
We will make no attempt to delineate or de- 
fine those experimental needs requiring use of 
nonhuman primates, but it is worth mentioning 
that such usage should be scrutinized extremely 
carefully. Only too frequently exotic and rare 
(some almost to the point of extinction) animals 
are used for experimentation that could be well 
satisfied by use of another laboratory animal. 
A number of the nonhuman primates are now 
included among the endangered species and 
their use should be carefully considered! 
MONKEYS AND APES 
Table I lists various species of nonhuman 
primates that are used in the laboratory. Cer- 
tain species, for example the rhesus monkey 
(Macaca mulatta), are more commonly em- 
ployed than others. In certain instances size, 
cost and availability, as in the case of the gorilla 
(Gorilla gorilla), precludes extensive employ- 
ment. In many instances the choice of simian 
employed for one or another investigative situa- 
♦♦This study has been partially funded by U.S.P.H.S. grants 
#RR05519, RR00278, RR00361, RR00451 and contracts #NIH 69-93 
and WHO grant Z2/181/27. 
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