Naegleria infection overview

Naegleria is a free-living amoeba commonly found in the environment in water and soil. Infection of humans is rare but serious. To prevent infection with Naegleria, precautions should be taken to ensure that water does not enter the nose when participating in recreational water sports.

Only one species (type) of Naegleria infects people: Naegleria fowleri.

Infection with Naegleria is very rare. However, when it does occur, infection is most common during the dry, summer months, when the air temperature is hot, the water is warm, and water levels are low. The number of infections increase during years characterized by heat waves.

After the start of symptoms, the disease progresses rapidly and usually causes death within about 5 days (range 1 to 12 days).

Naegleria fowleri causes the disease primary amebic meningoencephalitis (PAM), a brain infection that leads to the destruction of brain tissue. In its early stages, symptoms of PAM may be similar to symptoms of bacterial meningitis.

Initial symptoms of PAM start about 5 days (range 1 to 7 days) after infection. The initial symptoms may include headache, fever, nausea, or vomiting. Later symptoms can include stiff neck, confusion, lack of attention to people and surroundings, loss of balance, seizures, and hallucinations.

In Naegleria infections, the diagnosis can be made by microscopic examination of cerebrospinal fluid (CSF). A wet mount may detect motile trophozoites, and a Giemsa-stained smear will show trophozoites with typical morphology. Confocal microscopy or cultivation of the causal organism, and its identification by direct immunofluorescent antibody, may also prove useful. An increasing number of PCR-based techniques (conventional and real-time PCR) have been described for detection and identification of free-living amoebic infections in the clinical samples. Such techniques may be available in selected reference diagnostic laboratories.

Several drugs are effective against Naegleria fowleri in the laboratory. However, their effectiveness is unclear since almost all infections have been fatal, even when people were treated. Amphotericin B has been successfully used in some cases to treat PAM caused by Naegleria fowleri.

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