Herpesvirus saïmirisis

What is it?

Herpesvirus saïmirisis is a viral infection caused by Herpesvirus saimiri, a virus from the herpesvirus family that naturally affects squirrel monkeys (saimiris). In the saimiri, this natural host, the infection is most often silent and not serious: the virus remains hidden in the body (we speak of latency) without causing any apparent illness. This virus, however, takes on particular importance because it can be transmitted to other species of primates, in which it causes much more severe diseases such as lymphomas (cancers of the blood and lymph nodes). This is why this disease is mainly monitored in zoological parks and primate centers where several species coexist.

Commonly observed signs

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

Causes and risk factors

The disease is caused by a herpesvirus, Herpesvirus saimiri (HVS), which naturally infects the saimiri (Saimiri sciureus) without causing serious symptoms in this native species. The saimiri is what we call a “natural reservoir”: it carries the virus all its life, often silently, and can transmit it to other species of primates. The problem especially arises when this virus is transmitted to other species of monkeys, such as aotus (owl monkeys) or certain New World monkeys, in whom it then causes much more serious illnesses, including lymphomas (cancers of the lymphatic system) and leukemia. In the saimiri itself, the infection most often remains latent (dormant) throughout the animal's life, with possible reactivation in periods of stress or reduced immune defenses.

The main risk factor is cohabitation in captivity between carrier saimiris and other sensitive primate species, particularly in zoos, primatology centers or private collections. Stress, transport, an intercurrent illness or any situation weakening the saïmiri's immune defenses can promote reactivation of the virus that remains latent. High animal density and the sharing of equipment or enclosures between different species also increase the risk of cross-transmission.

Transmission

The virus is transmitted mainly by direct contact between animals, in particular by saliva, but also possibly by respiratory route or by contaminated equipment shared between enclosures. The most worrying transmission is that of the carrier saimiri to other more sensitive species of New World primates, particularly in captivity where contact between different species is possible.

Diagnosis and care

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

Treatment

There is no specific antiviral treatment to eliminate this virus once the animal is infected, as is the case for most herpesviruses. Management of a saimiri presenting clinical signs remains symptomatic and supportive, aiming to strengthen the general condition of the animal. In susceptible species developing lymphomas following contamination, specialized oncological treatment can be considered but is rarely curative.

Prevention

Possible complications

In saïmiri, direct complications are rare because the infection is most often without major clinical consequences. The main complications concern transmission to other more sensitive species of primates, in which malignant lymphomas, leukemia and severe damage to the general condition can occur which can lead to death. A very immunocompromised saimiri (weakened in its defenses) could theoretically present viral reactivation with more marked clinical signs.

When to see a veterinarian

Prognosis

In the saimiri itself, the prognosis is generally excellent: the vast majority of carrier animals live normally without ever developing clinical disease. On the other hand, the prognosis becomes very guarded to dismal in other species of accidentally infected primates, in whom the virus can cause cancers of the lymphatic system, which are often fatal.

Frequently asked questions

References

WOAH — Organisation mondiale de la santé animale (ex-OIE)

AVMA — American Veterinary Medical Association

Content reviewed by the TunisieVet editorial team · Updated 23 September 2026