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Primary Amebic Meningoencephalitis

By Richard D. Pearson, MD

Primary amebic meningoencephalitis is a rare, usually fatal infection of the central nervous system (brain and spinal cord) caused by Naegleria fowleri.

The amebas that cause this infection live in fresh, often stagnant water throughout the world. When people, usually children or young adults, swim in contaminated water, the amebas can enter the central nervous system through the mucous membranes of the nose. When they reach the brain, they cause inflammation, tissue death, and bleeding.


Symptoms begin within 1 to 2 weeks. Sometimes the first symptom is a change in smell or taste. Later, people have a headache, a stiff neck, sensitivity to light, nausea, and vomiting. They may become confused and sleepy and may have seizures. The infection can progress rapidly, causing death within 10 days.


  • A spinal tap and analysis of cerebrospinal fluid

  • Brain biopsy

Doctors suspect the infection in people who have symptoms and have been swimming recently in fresh water, but the diagnosis is difficult to confirm. A spinal tap (lumbar puncture) is done to obtain a sample of cerebrospinal fluid (the fluid that surrounds the brain and spinal cord). This test can exclude other possible causes of meningitis and brain infection, but doctors are not always able to find the amebas in the sample.

Sometimes a sample of brain tissue is taken to be examined under a microscope and analyzed (biopsied).

Other techniques are available in specialized laboratories and are more likely to detect the amebas. They include culture, polymerase chain reaction (PCR) to check for the genetic material of the ameba, and stains to identify ameba in brain tissue.


  • A combination of drugs

Because few people survive, determining the best treatment is difficult. Doctors typically use a combination of drugs including

  • Miltefosine, which must be obtained from the Centers for Disease Control and Prevention (CDC)

and one or more of the following:

Drugs Mentioned In This Article

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