viral disease Barbary macaque Transmissible to humans

Herpes B Virus Infection in Macaques

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Definition Signs Causes Transmission Diagnosis Treatment Prevention Complications When to see a vet Zoonosis Prognosis FAQ Sources Affected species

What is it?

Herpes B virus infection in macaques, also known as B herpes virus disease, is a viral infection that occurs widely in macaques, including Barbary macaques. In these primates, it often appears as small, mild sores in and around the mouth or in the genital area, resembling a cold sore in humans. The virus then remains hidden—or "latent"—in the animal's body for life, with flare-ups possible especially during times of stress. This condition is primarily concerning because of its strong potential for transmission to humans, where it can cause severe, sometimes fatal damage to the nervous system.

Key point

Although rarely severe in the macaque itself, this disease is classified among the most dangerous zoonoses transmissible by nonhuman primates, with a high risk of death in an infected human if treatment is not started quickly.

Commonly observed signs

These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.

Related signs — each one links to its page:

Mouth ulcers Excessive salivation Difficulty chewing Scabs and skin lesions Licking the genital area

In Barbary macaques, infection most often goes completely unnoticed. When signs do appear, they are mainly small blisters that develop into ulcers on the lips, mouth, tongue, or genitals, resembling a cold sore. These sores may be accompanied by difficulty eating or local discomfort, but the animal's overall condition usually remains good. The sores typically heal on their own within a few weeks, after which the virus remains dormant in the body, with possible flare-ups that may occur without any visible signs.

When to consult without delay

This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.

Causes and risk factors

The disease is caused by a virus belonging to the Herpesviridae family, called B herpes virus (or Macacine alphaherpesvirus 1), which is closely related to human herpes viruses but is capable of causing severe brain damage in humans. This virus naturally inhabits many macaques, including Barbary macaques, often without producing visible signs once the infection becomes established long-term in the animal's body.

Adult macaques, especially those living in groups where fighting and sexual contact are frequent, are most likely to develop active lesions. Stress, captivity, social group changes, or any decline in immune defenses can trigger virus reactivation in an animal that has been silently infected up to that point. For humans, the main risk factor is close contact with a macaque, particularly during handling, care procedures, or wildlife tourism.

Transmission

The virus spreads between macaques mainly through saliva, during biting, grooming, or sexual contact. Transmission to humans occurs through bite, scratch, spray of saliva or secretions onto broken skin or mucous membranes (eyes, mouth), or more rarely through simple contact with contaminated material. Transmission between humans is exceptional but has been documented.

Diagnosis and care

Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.

The veterinarian suspects infection when vesicles or oral or genital ulcers appear in a macaque, especially after a fight or contact with an infected animal. Definitive diagnosis relies on lesion samples sent to a specialized laboratory (virus detection by PCR, viral culture, or serology). Since this disease poses a serious risk to humans, any suspected animal must be handled with strict precautions and the laboratory must be notified of the suspicion so that appropriate biosafety measures can be applied.

Treatment

In the Barbary macaque, specific treatment is generally not necessary: lesions heal on their own. Local wound care or pain relief may be offered by the veterinarian if needed. No treatment can eliminate latent virus in the animal. In an exposed human, emergency antiviral treatment given by a physician can prevent progression to the severe neurological form.

Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.

Prevention

Prevention relies mainly on limiting unprotected direct contact between humans and macaques, including wearing gloves and appropriate protective equipment during any handling. Facilities housing Barbary macaques (zoos, sanctuaries, rehabilitation centers) must train staff on high-risk behaviors and proper response to bites or scratches. No vaccine is currently available for either animals or humans. Serological screening of captive animals and group management to reduce fighting and stress also help lower the risk of viral reactivation and transmission.

Possible complications

In the macaque itself, the disease usually remains mild, with skin or oral lesions healing within a few weeks. The most serious complications affect humans in contact with the animal: infection can progress to severe nervous system involvement, potentially fatal or leaving severe neurological damage if not treated very quickly.

When to see a veterinarian

Appearance of blisters or mouth or genital ulcers in the macaque.

Any bite, scratch, or splash of macaque saliva on a person requires immediate human medical evaluation.

Refusal to eat or excessive persistent drooling in the animal.

Unusual behaviour or lethargy associated with skin lesions.

Transmission to humans

This disease is a major zoonosis and potentially fatal to humans. Any exposure (bite, scratch, splash of saliva or fluid from a lesion onto a wound or mucous membrane) must be treated as a medical emergency: immediate and thorough washing of the exposed area, followed by urgent medical consultation, as early preventive treatment significantly reduces the risk of severe complications.

Prognosis

In the Barbary macaque, the prognosis is generally good: skin or mucous membrane lesions heal spontaneously and the animal remains a virus carrier without this significantly affecting its long-term health. However, the prognosis is very guarded for any human infected and not treated quickly, because of the risk of severe neurological involvement.

Frequently asked questions

Can a symptom-free Barbary macaque still transmit the virus?

Yes. The virus can be shed intermittently through saliva or genital secretions even in the absence of visible lesions, which makes any bite or scratch potentially risky.

Should all captive Barbary macaques be tested?

Serological screening is recommended for animals in close contact with humans (parks, sanctuaries, care centres) in order to adapt personnel protection measures accordingly.

What to do immediately if bitten or scratched by a macaque?

The wound must be washed thoroughly and at length with soap and water, then a doctor must be consulted urgently, reporting exposure to a macaque, as a preventive human treatment exists if started quickly.

Can the virus be permanently eliminated in an infected macaque?

No, like all herpes viruses, it remains latent for life in the animal's body once the infection is established; there is no treatment that completely eliminates it in monkeys.