Simian malaria (primate malaria)
Simian malaria is a parasitic blood disease that affects primates, including gibbons. It is caused by microscopic parasites called Plasmodium, transmitted by mosquito bites. These parasites invade and destroy the red blood cells of the infe...
What is it?
Simian malaria is a parasitic blood disease that affects primates, including gibbons. It is caused by microscopic parasites called Plasmodium, transmitted by mosquito bites. These parasites invade and destroy the red blood cells of the infected animal.\n\nIn gibbons, this disease can remain discreet for a long time or, on the contrary, cause severe anemia and serious complications. It is closely monitored in zoos and conservation centers because certain species of Plasmodium can also infect humans, making it a health concern shared between animals and humans.
Key point
Potentially serious illness that can be life-threatening if left untreated, particularly in cases of severe anemia.
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:
The signs vary depending on the strain of parasite and the general condition of the gibbon.\n\nWe most often observe fever in waves, marked depression and loss of appetite. The animal becomes tired, less active than usual.\n\nAt a more advanced stage, anemia caused by the destruction of red blood cells makes the mucous membranes (gums, around the eyes) pale. A yellowish discoloration of the skin or eyes (jaundice) may appear if the liver is affected.\n\nIn severe forms, tremors, convulsions or significant weight loss may occur. Without support, progression can be rapid and serious.
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 unicellular parasites of the genus Plasmodium, specific to primates. Several species of Plasmodium can infect gibbons and other monkeys, some of which are shared with humans.\n\nThe parasite multiplies in the animal's red blood cells, causing their cyclical destruction, which explains the characteristic bouts of fever.
Living in or near areas where Anopheles mosquitoes are present in large numbers increases the risk of exposure.\n\nYoung animals, weakened or stressed individuals (transport, recent captivity) and those whose immune system is already weakened are more vulnerable to a severe form of the disease.\n\nMoist, hot environments and with stagnant water favor the proliferation of mosquito vectors.
Transmission
Transmission occurs through the bite of Anopheles mosquitoes, which act as vectors. The mosquito bites an infected animal, then transmits the parasite to another individual during a subsequent bite.\n\nThere is no direct transmission between gibbons by simple contact; the mosquito is essential to the disease cycle.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The diagnosis is based on a blood test carried out by the veterinarian, in particular a blood smear allowing the parasite to be directly observed in the red blood cells under a microscope.\n\nAdditional tests, such as molecular biology analyses, can confirm the species of Plasmodium in question. A complete blood test also makes it possible to assess the degree of anemia and organ damage.
Treatment
Treatment is based on specific antiparasitic medications (antimalarials), prescribed and adapted by the veterinarian according to the species of parasite identified and the condition of the animal.\n\nSupportive care may be necessary in cases of severe anemia: fluids, nutritional support, or even transfusion in the most serious cases. Close veterinary monitoring is essential throughout the duration of treatment.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Prevention is mainly based on the fight against mosquitoes: mosquito nets suitable for enclosures, elimination of stagnant water, use of repellents authorized in animal environments.\n\nRegular health checks of new animals before their integration into a group makes it possible to detect an infection before it spreads.\n\nRegular veterinary surveillance, in particular routine blood tests, helps to identify an early infection in animals at risk.
Possible complications
Untreated severe anemia can lead to multiple organ failure. The liver and spleen may be affected, with a risk of rupture of the spleen in extreme cases.\n\nNeurological complications are possible with certain species of Plasmodium, manifesting as convulsions or disturbances of consciousness.
When to see a veterinarian
Persistent or intermittent fever in gibbon\nUnusual depression or refusal to eat\nPale mucous membranes or yellowish discoloration of the skin/eyes\nTremors or convulsions\nAny unexplained change in behavior in an animal living in a mosquito area
Transmission to humans
Certain species of Plasmodium affecting non-human primates can, in rare documented cases, infect humans, particularly through the bite of a mosquito that has previously bitten an infected animal. Caregivers and visitors to zoos in risk areas must respect the mosquito protection measures recommended by the health authorities.
Prognosis
The prognosis depends on the speed of treatment and the species of Plasmodium involved. Diagnosed early and treated correctly, the disease can be well controlled.\n\nIn the absence of treatment, severe forms with significant anemia or organ damage can be fatal, particularly in young or weakened animals.
Frequently asked questions
Can monkey malaria be transmitted directly from a gibbon to a human?
No, there is no direct transmission. The parasite needs a mosquito to pass from one individual to another, whether animal or human.
Can an infected gibbon recover completely?
Yes, with early diagnosis and appropriate antiparasitic treatment followed by a veterinarian, many gibbons recover well.
How do I know if my gibbon is at risk?
Animals living in areas where Anopheles mosquitoes are present, particularly in hot and humid climates, are most at risk. Regular veterinary monitoring allows this risk to be assessed.
Is there a vaccine for gibbons against this disease?
No, there is no vaccine available for this disease in gibbons at this time. Prevention is based on the fight against mosquitoes.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
OMS — Organisation mondiale de la santé
CDC — Centers for Disease Control and Prevention
Content reviewed by the TunisieVet editorial team · Updated 22 September 2026
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