parasitic disease Western gorilla Transmissible to humans

Simian Malaria in Gorillas

Find a veterinarian All western gorilla diseases

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

What is it?

Simian malaria is a parasitic disease caused by microscopic protozoans of the genus Plasmodium. These parasites infect the red blood cells. In western gorillas, several Plasmodium species specific to African great apes have been identified in recent years through genetic studies. The disease is transmitted by mosquitoes and affects gorillas living in the wild in central and west Africa. It is now known that the most dangerous human malaria, caused by Plasmodium falciparum, has its evolutionary origin in gorillas, making this disease particularly interesting for scientific research.

In gorillas, infection is usually silent or only mildly severe, as the animals have developed a degree of tolerance to these parasites through evolution.

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:

Fever Reduction Loss of appetite Pale mucous membranes Jaundice Fatigue Weight loss

Most infected gorillas show no visible signs of disease. Infection often remains chronic and discreet.

In rare cases, particularly in weakened, young, or already ill animals, fever, general lethargy, loss of appetite, and unusual fatigue may be seen.

Anemia (reduction in red blood cells) can develop if infection becomes significant, resulting in pale mucous membranes (gums, inner eyelids). Jaundice (yellowish discoloration) is possible in more severe cases, although these remain exceptional in wild gorillas.

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 single-celled parasites of the genus Plasmodium. In gorillas, several distinct species have been described, some very closely related genetically to Plasmodium falciparum, the agent of the most severe human malaria. These parasites multiply inside red blood cells, which they eventually destroy.

Gorillas living in areas with high densities of Anopheles mosquitoes, particularly in the humid tropical forests of central Africa, face the greatest exposure. Young animals, individuals in poor health, stressed animals, or those already affected by another disease appear more likely to develop symptomatic forms of the infection. The rainy season, which promotes mosquito breeding, increases the risk of transmission.

Transmission

The parasite is transmitted through the bite of mosquitoes of the genus Anopheles, which act as vectors. The mosquito becomes infected by biting an infected gorilla, then transmits it to another gorilla in a subsequent bite. There is no direct transmission between gorillas without passage through the mosquito.

Diagnosis and care

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

Diagnosis is based on a blood test performed by a veterinarian, with microscopic examination of a blood smear to detect parasites within red blood cells. Molecular biology techniques such as PCR are used in research to identify the specific Plasmodium species involved. In wild gorillas, diagnosis is most often made from non-invasive samples (faeces) as part of scientific studies.

Treatment

When treatment is necessary, particularly in a captive animal or sanctuary resident showing clinical signs, antimalarial medications may be prescribed by a veterinarian specializing in primate medicine. The choice of drug and monitoring must be strictly supervised by a professional; self-treatment is completely inadvisable in this protected and sensitive species.

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 controlling mosquito vectors in the animal's environment, especially in captivity or in sanctuaries: elimination of stagnant water, insecticide-treated nets, suitable repellents. In the wild, direct preventive measures are not feasible, as infection is part of the gorilla's natural ecosystem. Regular veterinary monitoring of captive or sanctuary populations allows early detection.

Possible complications

In rare severe cases, marked anaemia, general weakness, and increased vulnerability to other infections may occur. In an already weakened animal, the combination of malaria with another disease can worsen the overall outlook.

When to see a veterinarian

Persistent fever associated with unusual lethargy

Abnormally pale or yellowish mucous membranes

Prolonged loss of appetite without another identified cause

Marked fatigue or reluctance to move in an animal that is normally active

Any unusual sign in a young, elderly, or already weakened gorilla

Transmission to humans

The Plasmodium species that naturally infect gorillas are not known to readily infect humans under natural conditions. However, these parasites are being closely studied by scientific research because they are genetically very close to Plasmodium falciparum, which causes the most severe human malaria and is thought to be their evolutionary ancestor. Close and repeated contact between humans and wild great apes (via the same mosquito vectors) is theoretically a factor to monitor, although the risk of direct zoonotic transmission remains considered low based on current knowledge.

Prognosis

The prognosis is generally good, with the majority of infections remaining asymptomatic thanks to natural tolerance developed by the species toward its specific Plasmodium parasites. Symptomatic forms, which are rarer, generally respond favorably to appropriate veterinary care. The prognosis is more guarded in animals already weakened by other conditions.

Frequently asked questions

Is gorilla malaria dangerous for the animal?

In the vast majority of cases, no. Gorillas have developed natural tolerance to their own Plasmodium species and often remain carriers without showing signs of disease.

Can you catch malaria by approaching an infected gorilla?

The direct risk is considered very low. Malaria transmission requires a vector mosquito; there is no direct contamination between gorilla and human through simple contact.

Why are scientists so interested in this disease in gorillas?

Because genetic research has shown that Plasmodium falciparum, responsible for the deadliest form of human malaria, most likely originated from a Plasmodium ancestor found in wild gorillas.

How are gorillas protected against this disease in sanctuaries?

Mainly by limiting the presence of mosquitoes around enclosures: elimination of standing water, mosquito nets, and regular veterinary monitoring of animals.