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.
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.
Medical Author:
Charles P. Davis, MD, PhD
Medical Editor: William C. Shiel Jr., MD, FACP, FACR
Yes, there are things that can eat your brain: the Naegleria fowleri story.
So far this summer, three people have died from
Naegleria fowleri, termed the
"brain-eating amoeba." Naegleria fowleri is the genus and species name of an
ameboflagellate that causes primary amebic meningoencephalitis (PAM) in humans,
mainly in children and young adults. It exists in three forms, free-living
cysts, trophozoites, and flagellated forms. Its life cycle is mainly in the cyst
to trophozoite to cyst cycle (see image) and resembles other amoeboid genera
like Acanthamoeba. The organism was discovered in Australia in 1965 by Drs. M.
Fowler and R. Carter but probably has been occasionally infecting humans for
centuries.
Fortunately, humans are rarely infected with Naegleria fowleri. Most doctors
do not ever see or diagnosis this infection in any of their patients. Although
the organisms can be found worldwide, mainly in warm waters (lakes, rivers, hot
springs, power plant warm water discharge pools) that have loose sediment, are
stagnant or contaminated with stirred up bottom sediment, or even in poorly
chlorinated swimming pools, only about 121 cases have occurred in the US
according to the CDC. Only one person has reportedly survived a diagnosed case
of primary amebic meningoencephalitis caused by this parasite.
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.
What is Naegleria fowleri?
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
Headaches can be divided into two categories: primary headaches and secondary headaches. Migraine headaches, tension headaches, and cluster headaches are considered primary headaches. Secondary headaches are caused by disease. Headache symptoms vary with the headache type. Over-the-counter pain relievers provide short-term relief for most headaches.
Nausea is an uneasiness of the stomach that often precedes vomiting. Nausea and vomiting are not diseases, but they are symptoms of many conditions. The causes of vomiting differ according to age, and treatment depends upon the cause of nausea and vomiting.
Although a fever technically is any body temperature above the normal of 98.6 degrees F. (37 degrees C.), in practice a person is usually not considered to have a significant fever until the temperature is above 100.4 degrees F (38 degrees C.). Fever is part of the body's own disease-fighting arsenal: rising body temperatures apparently are capable of killing off many disease- producing organisms.
Epilepsy is a brain disorder in which the person has seizures. There are two kinds of seizures, focal and generalized. There are many causes of epilepsy. Treatment of epilepsy (seizures) depends upon the cause and type of seizures experienced.
Encephalitis is a brain inflammation that causes sudden fever, vomiting, headache, light sensitivity, stiff neck and back, drowsiness, and irritability. Meningitis is an infection that causes inflammation of the meninges that surround the brain and spinal cord. Symptoms of meningitis include high fever, headache, nausea, vomiting, and stiff neck.
Recreational Water Illnesses (RWIs) are caused by germs spread by breathing in mists or aerosols, swimming, or having contact with contaminated water in hot tubs, water parks, water play areas, fountains, lakes, rivers, oceans, and swimming pools. Diarrhea is the most commonly reported recreational water illness. Diarrheal illnesses are caused by germs such as Crypto, Shigella, Norovirus, E. coli, and Giardia. Prevention of water born illnesses is key to avoid infection. Avoid swallowing water and practice good hygiene habits are a must.
Fever refers to an elevation in body temperature. Technically, any body temperature above the normal oral measurement of 98.6 F (37 C) or the normal rectal temperature of 99 F (37.2 C) is considered to be elevated. However, these are averages, and
one's normal body temperature may actually be 1 F (0.6 C) or more above or below the average of 98.6 F. Body temperature can also vary up to 1 F (0.6 C) throughout the day.
Fever is not considered medically significant until body temperature is above 100.4 F (38 C). Anything above normal but below 100.4 F (38 C) is considered a low-grade fever. Fever serves as one of the body's natural defenses against bacteria and viruses which cannot live at a higher temperature. For that reason, low fevers should normally go untreated, unless accompanied by troubling symptoms.
Also, the body's defense mechanisms seem to work more efficiently at a higher temperature. Fever is just one part of an illness...
Yes, there are things that can eat your brain: the Naegleria fowleri story.
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