Naegleria fowleri

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Medical Author:

Mary D. Nettleman, MD, MS, MACP

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.

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Medical Editor:

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 is an amoeba that lives predominately in warm, fresh water.
• Naegleria fowleri is acquired by people when infected water is forcibly aspirated into the nose. This can occur through recreational swimming, diving, or during sports like water skiing.
• Once acquired, the amoeba travels into the brain, causing primary amoebic meningoencephalitis (PAM).
• PAM is very rare, and there are only a few cases reported each year in the United States.
• People with PAM initially experience changes in smell or taste. The disease advances rapidly, causing fever, stiff neck, and coma.
• Infection is diagnosed by examining spinal fluid under the microscope to identify the amoeba. Naegleria fowleri may also be grown in the laboratory, although this takes several days. Newer tests based on PCR technology are being developed.
• The treatment of choice is an intravenous drug called amphotericin B. Amphotericin B may also be instilled directly into the brain.
• More than 95% of cases of PAM are fatal despite treatment.

Naegleria fowleri is an amoeba that lives in fresh water and soil. The organism goes through three stages in its life cycle: cysts, flagellates, and trophozoites. It is the trophozoite form that causes human disease. Naegleria are "thermophilic," meaning that they prefer warmer water. However, the cysts are able to survive for months in very cold water. Thus, Naegleria infection is found both in tropical and temperate climates.

Although there are many species of Naegleria, including Naegleria gruberi, only Naegleria fowleri causes human infection. There are other free-living amoebas that cause human disease, including Acanthamoeba.

Picture of Naegleria fowleri surrounded by white cells in spinal fluid; Source: CDC