Summary of Risks Associated with Herpes B Virus in
Macaques.
KEY POINTS
 Herpes B virus causes few symptoms in infected macaques and does not
significantly impact their welfare.
 Infection of humans with Herpes B virus is very rare with less than 50 cases
recorded despite thousands of human exposures.
 No cases of human infection with Herpes B have ever occurred in zoos.
 Currently all human cases have occurred secondary to contact with Macaca
mulatta, all in laboratories in the US.
 No documented cases of transmission have occured from other Macaca spp.
 However, if transmitted to a human, B virus infection has a nearly 80% casefatality rate.There are no vaccines.
 All Asian macaques should be assumed to be infected
 Implementing comprehensive biosecurity practices significantly reduces risk
of human exposure.
 All zoos should have a written exposure protocol.
 Staff should be trained in disease prevention and action in the event of
exposure.
Introduction
Herpes B virus occurs as a enzootic, life-long and generally asymptomatic infection
of macaques. Barbary Macaques (Macaca sylvanus) have never been reported be
infected with Herpes B Virus despite testing of large groups of wild and zoo animals.
At present the infection status of most groups of Asian Macaca species in the
managed programmes (and the wild) is unknown.
Infection in Macaques
The disease in macaques is usually mild and self-limiting. Clinical disease is
characterised by the appearance of small vesicles on the lips or in the oral cavity.
The vesicles typically rupture, scab and heal within 7-14 days. Conjunctivitis or nasal
discharge may also be seen. Animals will start shedding virus (i.e. be infectious to
other macaques and humans) at this time both from the site of infection and also
from other body secretions. Gradually their body mounts an immune response and
the virus goes into dormancy in nerve cells. The animals are likely to remain infected
for life. Re-activation of latent infection, with viral shedding ± clinical signs, can occur;
the factors leading to this are poorly understood, but may include stress, fever, injury
and immunosuppression
Surveillance and Testing Regimes.
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Testing macaques for herpes B virus infection is not straight forward. There is
no herpes B specific antibody test available in Europe. False negative results
are possible because latently-infected individuals will only maintain an
antibody response for a period of 6-12 months after viraemia and hence
infected animals can test negative with antibody detection tests. So if the
animal did not shed virus for a long time it is possible that you will not detect
any antibodies (false negative results) but when they start shedding the can
infect the others in the group.
Negative tests do not indicate an individual, or colony, is not infected with
herpes B virus, and should not be relied upon for risk management purposes.
However false positives are very unlikely.
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All macaque deaths should be thoroughly investigated The necropsy should
preferably be carried out in a biohazard safety cabinet. Zoos which are
unable to meet sufficient biosecurity standards for necropsy of macaques
should consider submitting the body to an appropriate diagnostic laboratory.
Zoos undertaking diagnostic testing should discuss their testing regimes and
protocols with the OWM TAG Vet advisors before commencing and should
inform the vet advisors of results.
Infection in Humans
 Transmission to humans is by contamination of wounds or mucous membranes
with body secretions or tissues from infected animals. B-virus disease in
humans usually results from macaque bites or scratches Incubation periods
may be as short as 2 days, but more commonly are 2 to 5 weeks.
 Vesicles on the skin develop at the site of inoculation 1–5 days post exposure
in many cases, followed by swelling of local lymph nodes. Itchy skin and pain
at the inoculation site may be intense. Other signs of infection include
influenza like symptoms, such as persistent fever, headache, nausea,
vomiting, and muscle pain.
 The disease progresses quickly to paralysis, numbness dizziness, double
vision, difficult swallowing and confusion, respiratory difficulties, and coma.
 Death occurs 10–14 days post exposure in 70–80% of herpes B virus
infected humans.
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Minimising exposure risk to humans
 Control of Herpes B infection in humans must focus on prevention of
exposures and good education of staff.
 No protective vaccines are available
 Institutions should identify and collaborate with a local medical practitioner for
establishing policy and protocols, and coordinating the response to an
exposure event.
 All personnel, including contractors, students and volunteers, should receive
appropriate training on the risk associated with herpes B virus, appropriate
methods of restraint, and the use of protective clothing. Personnel should be
required to sign that they acknowledge comprehension of institutional
guidelines. Access to macaque areas should be restricted to people that have
completed this process.
 Macaques should not be utilised for direct contact experiences, such as
handling or feeding, for the general public.
 Asian macaques should not be housed in walk-through exhibits.
 Where Barbary macaques are housed in walk-through exhibits contact with
the macaques and macaque body fluids (eg urine, saliva, faeces) should be
avoided.
 Personnel coming into contact with macaques or their biological products
should wear appropriate clothing that minimises the risk of contamination of
skin and mucous membranes (e.g. eyes, mouth) with macaque secretions or
excretions, and prevents scratches. This should include (at a minimum) longsleeved and long-legged garments.
 Strict personal hygiene is essential for herpes B virus risk management.
Hand washing is the most effective means of preventing transmission of
zoonotic diseases generally. Disposable gloves should be used in higher risk
situations, but they do not negate the importance of hand washing after
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working around macaques, or after servicing areas potentially contaminated
by macaques.
The use of high pressure hosing in macaque areas should be avoided to
minimise the production of aerosols from faeces, saliva and other
secretions/excretions.
Herpes B virus is readily destroyed by common detergents and disinfectants;
these should be used when cleaning enclosures and associated equipment.
Direct handling of macaques should be minimised. Capturing, restraining or
otherwise handling fully conscious macaques is not recommended.
Macaques should be physically restrained in a squeeze-cage and hand
injected with a chemical restraint agent prior to handling.
Behavioural conditioning of macaques is a practical and very useful technique
to complement physical and chemical restraint options.
All veterinary procedures on macaques should be carried out by suitably
experienced and competent veterinarians with a full understanding of herpes
B risk and risk management. Veterinary procedures should only be performed
on animals that are sufficiently chemically restrained.
Post exposure prophylaxis and first aid
 Humans should be considered as potentially exposed following any wound
received from a macaque or contamination of mucous membranes or broken
skin by macaque excretions and secretions.
 The adequacy and timeliness of wound decontamination procedures are the
most important factors in preventing the risk of infection after herpes B virus
exposure.
 Institution specific post-exposure first aid protocols should be developed in
conjunction with the zoos medical practitioner.
 Information sheets containing basic information about herpes B virus, postexposure treatment protocols, and contacts for further information should be
readily accessible and accompany the patient to the medical facility. The
identified medical practitioner(s) may be unavailable at the time and the
patient could be seen by a doctor unfamiliar with herpes B virus.
For further information and advice please contact the Old World
Monkey Taxon Advisory Group Veterinary Advisors
Matt@zooandwildlifesolutions.com
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