Naegleria fowleri Infection (Brain-Eating Amoeba Infection)

  • Medical Author:

    Sandra Gonzalez Gompf, MD, FACP is a U.S. board-certified Infectious Disease subspecialist. Dr. Gompf received a Bachelor of Science from the University of Miami, and a Medical Degree from the University of South Florida. Dr. Gompf completed residency training in Internal Medicine at the University of South Florida followed by subspecialty fellowship training there in Infectious Diseases under the directorship of Dr. John T. Sinnott, IV.

  • Medical Editor: Charles Patrick Davis, MD, PhD
    Charles Patrick Davis, MD, PhD

    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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Naegleria fowleri:
Brain-Eating Amoeba

Risk of Infection and Symptoms

Brain-Eating Amoeba signs and symptoms may start about 1 day to 1 week after exposure; initially symptoms may include:

  • changes in smell and taste,
  • headache,
  • fever,
  • stiff neck,
  • nausea, and vomiting.

The patient may have confusion, ataxia (wobbliness), and seizures; and rapidly worsen over about 3 to 7 days with death occurring about 7 to 14 days after exposure.

Naegleria fowleri (brain-eating amoeba) infection facts

  • Naegleria fowleri is an amoeba that is common throughout the world and lives in soil and freshwater. When conditions are favorable, usually summer, it multiplies rapidly.
  • Naegleria fowleri causes infection when water containing amoebae forcefully enters the nose. This can occur through recreational swimming, jumping, diving, or during sports like water skiing.
  • Neti pots or nasal rinsing with unboiled tap water has also caused disease. Swallowing contaminated water does not cause disease.
  • The amoeba consumes and digests its way into the brain, causing primary amoebic meningoencephalitis (PAM). Naegleria fowleri is often called the "brain-eating amoeba," which is unfortunately fairly accurate.
  • PAM is uncommonly reported, but it has a 99% fatality rate and usually affects young, active, healthy people. As of August 2016, 40 cases have been reported in the United States since 2006, up to eight per year.
  • Most cases have been reported in southern States, however in recent years, cases are being reported as far north as Minnesota. With increasing temperature trends, Naegleria habitat is expanding, and more cases may occur in unexpected places.
  • People with PAM have a rapidly progressive illness with fever, headache, stiff neck, and finally coma and death.
  • PAM looks no different than bacterial or viral meningitis. Because bacterial meningitis is common, testing and treatment routinely focuses on bacteria. PAM may look like bacterial meningitis without the bacteria, and doctors may not know why antibiotics are failing.
  • The most important clue is exposure to warm freshwater within the prior two weeks. Anyone with such exposure who develops symptoms of meningitis should seek care emergently and tell the doctor about it.
  • Naegleria is easy to miss even when doctors are looking for it. Like bacterial meningitis, diagnosis requires a spinal tap (lumbar puncture). The spinal fluid must be examined specifically for amoebae; these can be hard to detect without highly specialized tests not available in most hospitals.
  • The treatment of choice is intravenous amphotericin B with a combination of antimicrobials. Miltefosine (Impavido) is a drug that has shown promise and is now available and recommended in the regimen.
  • Treatment should be started without delay. An infectious diseases doctor should be consulted immediately even if the diagnosis is only suspected. The CDC Emergency Operations Center offers 24/7 assistance and should be consulted immediately at 770-488-7100.
  • Prevention of PAM is straightforward. Untreated freshwater of any kind, especially during hot months or in hot springs, should be kept out of the nose. Entering the water during these periods should be avoided, the head should be kept dry above water, or nose clips should be used.
Medically Reviewed by a Doctor on 8/18/2016

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