Probably the most dangerous diseases, because they are so difficult to
diagnose and treat, are those of viral origin. Many viral diseases,
such as hepatitis or herpes B, can be transmitted from animal to man. A
virus may be latent in one species of primate, with little or no
disease, yet be fatal in another species of primate, including man.
Herpesviruses have been found in many different species of primates. Some herpesviruses can produce a highly fatal systemic
disease. Most primate herpes viruses are latent in one reservoir host
species and fatal in another species. Overt disease in the host species
rarely occurs other than as a mild skin lesion that is quickly
self-limiting. The most important of the zoonotic diseases is herpes B
virus or Herpes simiae.
Herpes simiae (herpes B) produces a mild disease in some species of
monkeys that is analogus to the cold sores caused in humans by the virus
Herpes hominis (simplex), to which B virus is immunologically related.
in man, B virus can be fatal, causing as acute ascending myelitis. Of
the 20 plus cases reported, only two patients have survived, and there
is some question on the confirmation of B virus in those two. Thus, the
virus has a possible mortality rate of 100 per cent in patients who
develop clinical disease.
Under natural conditions, the virus seems limited to the macaques, with
both the rhesus and cynomolgus considered primary natural hosts;
however, other macaque species are also incriminated from results of
serologic testing. As high as 25 per cent of macaques, both imported
and domestically bred, have antibodies to herpes B virus. A short
incubation period of 4 to 10 days is required from initial exposure. As
with Herpes hominis, recurrent infection can occur even in the presence
of antibody; thus, all macaques at any time should be considered
potential carriers. As with other herpes infections, viral shedding
probably occurs only during periods of active lesions. The lesions in
the primates can be difficult to detect because they are usually on the
mucosa of the buccal cavity. There may be vesicles or ulcers around the
lips and external nares, with an appearance very similar to the cold
sore of man; however, the most common site is the tongue. The lesion
resolves quickly and often goes unnoticed by the handler. A rate of 2
to 3 per cent has been reported for clinical evidence of lesions in the
macaque at any one time.
The primary transmissions are from monkey bites and aerosolization of
the virus. Most human infections have resulted from laboratory
accidents and monkey bites; however, one case was thought to have been
caused by droplet spread. The hazard to the practitioner and the owner
makes it imperative that macaques not be kept as pets and that the risk
be explained to the owner. Any macaque being handled should be sedated with Ketamine Hydrochloride. Face masks and rubber gloves should be used to prevent possible spread. Serologic testing is available from primate reference services to determine the presence of Herpes simiae will remain negative unless brought into contact with a primate shedding the virus. The virus can also cause a fatal disease in the bonnet
monkey (M. radiata).
Two other herpesviruses, Herpesvirus saimiri and Herpesvirus ateles,
which are found in the squirrel and spider monkey, respectively, are
oncogenic in other nonhuman primates, causing neoplasms of
lymphoreticular origin upon injection. The incidence of antibody to H.
saimiri in wild-trapped squirrel monkeys approaches 100 per cent;
however, H. saimiri and H. ateles are NOT considered zoonotic hazards to human beings. A recent survey by NASA, using an indirect
immunofluorescence test, showed NO positive serologic response to H.
saimiri in human beings frequently exposed to animals shedding the
virus. Similar negative data exist for H. ateles. These negative
findings are mentioned here because of the popularity of New World
monkeys, especially squirrel monkeys, as pets.