Herpes simplex viruses of primates
Impact of herpes simplex viruses, including Herpes B virus, on the health of humans and non-human primates
Simplexviruses usually do not cause disease in their natural hosts, in species other than their natural hosts a number of simplex viruses can, however, cause severe disease.
Herpes simplex viruses infect humans (e.g. Herpes Simplex Virus 1, HSV-1) and non-human primates. They are well adapted to their natural hosts. Therefore, they usually elicit no or only mild symptoms in their natural hosts. Generalized infection and severe disease are rare. If, however, some of these viruses are transmitted to species that are not their natural host (e.g. transmission of monkey viruses to humans), then severe disease can occur.
Transmission of Herpes B virus of Rhesus monkeys (Macacine alphaherpesvirus 1) to humans can have severe consequences: persons affected can develop encephalomyelitis (inflammation of the brain and spinal cord). Untreated this is lethal in approximately 70-80% of the cases. To date, 50 cases of disease have been reported; at least 20 of which took a fatal course. The risk of fatal disease can be reduced by early application of antiviral therapy, for instance Valacyclovir and Ganciclovir.
Important questions regarding Herpes B virus infection are still not solved: It is not known why nearly all of the documented cases of disease following Herpes B virus infection occurred in the USA, primarily in Primate Centers. Furthermore, it is not clear why no cases of disease have been observed in persons in contact with free-ranging macaques.
Confirmation of Herpes B virus infection is typically obtained by amplification of viral genetic information and examination of the blood for the presence of antibodies. In case of the detection of antibodies, it is important to keep in mind that only limited conclusions can be drawn from negative results: formation of antibodies in infected animals can be delayed or the amount of antibodies produced can fall below the limit of detection. Re-isolation of the virus is possible. However, it requires Biosafety level (BSL) 3 (Germany) or 4 (USA) laboratories and is not always successful. In case of potential Herpes B virus infection in humans, the differentiation of antibody responses to Herpes B virus und HSV-1/HSV-2 poses additional difficulties. Appropriate diagnostics for human samples is available at the Georgia State University, Atlanta, USA (http://biotech.gsu.edu/virology/).
Additional information for veterinarians
Simplex viruses isolated from non-human primates include the following:
- Herpes B virus of macaques
- SA8 of African green monkeys
- Herpes-Virus-Papio-2 (HVP-2) of baboons
- Saimiriine herpesvirus 1 of Squirrel monkeys (SaHV-1)
Small and great apes also harbor species-specific simplex viruses.
The viruses first infect mucosal cells and then establish a latent infection in sensory ganglia. Sporadic reactivation results in the generation of progeny virions, which are found in various body fluids. The saimiriine herpesvirus 1 (SaHV-1) of Squirrel monkeys can cause severe disease upon transmission to marmosets (Callithrix spp), tamarines (Saguinus spp) and owl monkeys (Aotus trivirgatus). Infection of new world monkeys and prosimians with HSV of humans and with herpes B virus can result in severe disease.
The results of antibody-based diagnostic tests need to be interpreted with care: The generation of antibodies in infected animals can be delayed and antibody levels can fall below the limit of detection. Direct detection of Herpes B virus (and other simplex viruses) by PCR is extremely difficult, as the virus persists in the trigeminal ganglia. In saliva, the virus can be detected only during periods of active replication. In general, the virus can be detected in blood only when it actively replicates.
References
Eberle R, Jones-Engel L. Understanding Primate Herpesviruses. J Emerg Dis Virol. 2017 Mar;3(1).
Rohrman M. Macacine Herpes Virus (B Virus). Workplace Health Saf. 2016 64(1):9-12.
HERPES B VIRUS - European Association of Zoo and Wildlife Veterinarians - Transmissible Diseases Handbook 2019; Fact Sheet V14.11
HERPES HOMINIS VIRUS, HERPES SIMPLEX VIRUS - European Association of Zoo and Wildlife Veterinarians - Transmissible Diseases Handbook 2019; Fact Sheet V14.12
HERPESVIRUS TAMARINUS (Herpesvirus T, Herpesvirus platyrrhinae, Herpesvirus saimiri 1, Saimirine herpesvirus 1) - European Association of Zoo and Wildlife Veterinarians - Transmissible Diseases Handbook 2019; Fact Sheet V14.14