Naegleria fowleri, explained

What is it

Naegleria fowleri is a single-celled organism that belongs to a group called protozoa. Amoebas are usually found in water, soil and moist environments, and most of them are harmless. Naegleria fowleri is the exception: it lives in warm freshwater such as lakes, rivers, hot springs and poorly maintained pools, and it is dangerous and often fatal. It is commonly called the “brain-eating amoeba.”

How the amoeba causes harm

Infection happens when contaminated warm freshwater enters the nose. The amoeba attaches to the olfactory nerves and travels through the cribriform plate, the thin bone that separates the nose from the brain. Once it reaches the brain it multiplies and damages tissue, attaching to cells and releasing enzymes that break down what surrounds them. At the same time, the body’s immune response causes intense inflammation and swelling.

Together, this direct tissue damage and severe inflammation lead to Primary Amebic Meningoencephalitis (PAM), a rare but rapidly progressing and often fatal brain infection.

Symptoms

Early symptoms appear first, and are often mistaken for meningitis:

• Headache
• Fever
• Nausea
• Vomiting
• Neck stiffness

As the infection progresses, later symptoms set in:

• Confusion and difficulty concentrating
• Sensitivity to light
• Loss of balance or coordination
• Drowsiness and hallucinations
• Seizures and altered mental status
• Coma

Symptoms typically begin 1 to 12 days after exposure. Because the early signs are nearly identical to meningitis, PAM is often misdiagnosed at first as bacterial or viral meningitis.

Diagnosis and treatment

Treating PAM requires immediate, aggressive intervention, because the disease moves so quickly. Doctors typically use a combination of medications, including Amphotericin B, the primary drug used to kill the amoeba, along with Miltefosine, which has been linked to several survival cases. Other drugs such as Fluconazole, Azithromycin and Rifampin may be added as part of combination therapy.

Patients also need intensive supportive care in an intensive care unit (ICU), where teams closely monitor and manage brain swelling, seizures, breathing difficulties and other complications. Early diagnosis and prompt treatment are critical, as they offer the best chance of survival.

This article is part of Weekly Insights, written to make medical topics clear, not clinical. It isn’t medical advice; for anything about your own health, talk to a doctor.

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