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.

What are signs and symptoms of a Naegleria fowleri infection?

After exposure to a contaminated water source, symptoms of PAM develop within two to 12 days of exposure, usually within one week (incubation period). Initial symptoms may include disturbance of taste or smell, but this may not be noticed. Most cases begin with

As the illness progresses over several hours to a few days, most cases describe

The infection progresses so quickly that the disease may not be diagnosed until after death if an autopsy is performed. Most victims die within two to four days of first symptoms from severe inflammation and swelling of the brain.

What types of specialists treat Naegleria fowleri infections?

The first health professional a person with PAM sees may be a primary-care provider such as a pediatrician, family medicine doctor, adult-medicine doctor, or nurse practitioner, but most go to an emergency room when symptoms like headache and fever are severe or are not going away. People with suspected PAM are usually hospitalized under the care of a personal physician, a hospitalist, or a critical-care doctor and an infectious-disease doctor often assists with evaluation and treatment decisions. In addition, a physician skilled in intrathecal pump placement is usually consulted.

How do health-care professionals diagnose a Naegleria fowleri infection?

Naegleria fowleri should be quickly suspected in people with exposure to freshwater who have the 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, but brain scan may be normal. It is important not to delay a spinal tap if at all possible while waiting for a brain scan. If performed early, the spinal fluid may not suggest serious infection, and some victims were sent home from the emergency room, only to return with worsening disease. If suspicion is high, the spinal tap should be repeated in eight to 12 hours. Spinal fluid reflects inflammation with elevated levels of white blood cells and red blood cells. Routine Gram's staining does not detect the amoeba, however it may be seen on the routine Wright-Giemsa stain that is performed for the cell count. A wet mount of spinal fluid must be performed immediately to look for the moving amoeba under the microscope. The amoeba do not move unless the fluid is warmed. They will also move if a drop of distilled water is added to spinal fluid on the slide. This examination may be unsuccessful if there are many white blood cells due to intense inflammation; amoeba and white blood cells appear very similar to most technicians who are not experienced in looking for Naegleria.

The CDC Emergency Operations Center offers 24/7 assistance with diagnosis and should be consulted immediately at 770-488-7100.

Definitive tests for N. fowleri infection are done in only a few labs in the country, including the CDC. 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 on a petri dish that is covered with a layer of bacteria. The culture is then observed for winding trails caused by the amoebae consuming the bacteria. This is not routinely done.

The CDC PCR test is highly sensitive and specific for Naegleria fowleri, meaning it picks up even small numbers of amoebae and is rarely negative if the amoeba is truly present.

Medically Reviewed by a Doctor on 8/18/2016

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