972 
ANIMAL DISEASES 
upon interpretation of data is without question 
manifold. The relationship of these agents to 
overt human and colony health has been stressed 
throughout this discussion. 
A number of the simian virus isolates, mostly 
adenoviruses (SAT, SV20, SV33, SV34, SV37, 
SV38) and SV40 (a papovavirus) have been 
shown to be oncogenic in newborn hamsters 
and other rodents. It should be emphasized 
that no known tumors have ever been attributed 
to any of these agents in man or other primates. 
SV40 has been given to thousands of recipients 
of both live and dead poliovirus vaccine as an 
unknown contaminant. Many of these individ- 
uals have responded with development of anti- 
body not only to the poliovirus strains but to 
SV40 as well. 
In conclusion, numerous viruses are now rec- 
ognized as persisting within host tissues for 
long periods of time even to the duration of 
the animal's life. In the course of this discus- 
sion, we have alluded to certain of these as 
found within simian tissues, for example, her- 
pesviruses. Obviously, there are others! We 
have mentioned the ability of herpesviruses to 
produce devastating disease when invading an- 
other animal species. It appears that this virus 
group has another capability, that of becoming 
quiescent and producing latent infections. Im- 
munosuppression frequently results in the 
activation of these viruses: herpes simplex, 
cytomegalovirus, varicella in man and other 
herpesviruses in different animals. Activation 
of these viruses is frequently seen in patients 
with immunologic deficiencies which would 
strongly suggest that the immune mechanism 
may be an important factor in maintaining the 
latent state of these viral agents. 
One may only speculate at this time regarding 
the presence of all these simian viruses within 
the tissues and body cavities of monkeys and 
apes. The vast majority of these organisms do 
not appear to be related to anything specific — 
or even nonspecific. It is contrary to the orderly 
nature of biology to maintain a system of little 
purpose. Are these organisms simply without 
purpose or are they, like those involved in 
producing latent infections, awaiting their op- 
portunity to become overt and produce disease 
— or perhaps cancer? 
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