Naegleria fowleri Infection (Brain-Eating Amoeba Infection)

  • Medical Author:
    Mary D. Nettleman, MD, MS, MACP

    Mary D. Nettleman, MD, MS, MACP is the Chair of the Department of Medicine at Michigan State University. She is a graduate of Vanderbilt Medical School, and completed her residency in Internal Medicine and a fellowship in Infectious Diseases at Indiana University.

  • Medical Author: Jeremy Cauwels, MD, FACP
  • 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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How is a Naegleria fowleri infection diagnosed?

Naegleria fowleri should be suspected in people, especially children, with exposure to freshwater who have symptoms of meningitis or meningoencephalitis listed above. The characteristics of the presentation may be nonspecific at first, leading clinicians to suspect more common diseases such as bacterial or viral meningitis. Routine tests may show a high blood white cell count and images of the brain may show inflammation, but neither of these are specific to PAM. A spinal tap will be done and the spinal fluid often shows elevated levels or white cells and red cells. Routine staining (Gram staining) does not detect the amoeba. Thus, it is important to do a wet mount to look for the motile amoeba under the microscope.

Definitive tests for N. fowleri infection are done in only a few labs in the country. They use one of the following three methods:

  1. N. fowleri nucleic acid tests in CSF or biopsy tissue using PCR
  2. N. fowleri antigen tests in CSF or biopsy tissue using immunohistochemistry (IHC)
  3. It is also possible to culture N. fowleri, but this must be done in the presence of bacteria and at higher temperatures, which is not routinely done in most laboratories.

What is the treatment for a Naegleria fowleri infection?

Because Naegleria meningoencephalitis is rare, there are no studies comparing one treatment regimen to another.

The treatment of choice is amphotericin B, which is an intravenous drug usually used for fungal infections. In addition to intravenous treatment, amphotericin B can be instilled directly into the brain (intrathecally). Unfortunately, amphotericin alone often fails, which has led clinicians to use additional drugs. It is strongly recommended that an infectious-diseases expert be consulted to guide therapy. The Centers for Disease Control and Prevention has a supply of a newer agent called miltefosine, which has shown promise in a limited number of recent cases. Miltefosine can be acquired by calling the CDC Emergency Operations Center at 770-488-7100.

Other drugs such as rifampin (Rifadin), voriconazole (Vfend), or azithromycin (Zithromax, Zmax) have activity against Naegleria fowleri and may sometimes be used in combination with amphotericin B. However, there are no scientific studies available to determine the clinical efficacy of these medications and no official recommendation for their use.

Medically Reviewed by a Doctor on 4/8/2015

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