Primary amebic meningoencephalitis (PAM) is a rare brain infection caused by Naegleria fowleri. Only a few people are diagnosed with PAM in the United States each year.
N. fowleri is a free-living ameba. An ameba is a single-celled living organism that is too small to be seen without a microscope. It is commonly referred to as a brain-eating amoeba.
Causes
Infection with Naegleria fowleri typically occurs when the ameba enters the body through the nose. The ameba travels up the nose to the brain and spinal cord where it destroys the brain tissue.
Generally, exposure to the ameba occurs when people use warm freshwater for vigorous activities like swimming, diving, or other rigorous activities in freshwater.
Two cases of PAM in the U.S. have been linked to the use of household tap water for irrigation of sinuses. It is unknown why certain persons become infected with the amebe while millions of others exposed to warm recreational fresh waters do not, including those who were swimming with people who became infected.
Symptoms
In its early stages, symptoms of PAM are typical meningitis symptoms, including headache, fever, and stiff neck.
After the start of symptoms, the disease progresses rapidly.
Risk Factors
Fresh water exposure – Most N. fowleri infections occur when people swim or submerge their heads in warm fresh water like lakes, ponds, or rivers.
Tap water exposure – PAM may also occur when people use contaminated tap water to rinse their sinuses for religious or health reasons. In very rare instances, people have become infected from recreational water like splash pads and surf parks that didn’t have enough chlorine.
Geographic location – In the U.S., most infections have been linked to swimming in warm, southern states. However, evidence suggests the range of N. fowleri is expanding northward as the climate warms.
Treatment
Several drugs are effective against N. fowleri in the laboratory. However, their effectiveness is unclear since almost all infections have been fatal, even when people were treated.
Prevention
The only known way to prevent Naegleria fowleri infections is to refrain from water-related activities. However, some common-sense measures that might reduce risk by limiting the chance of contaminated water going up the nose include:
- Avoid water-related activities in bodies of warm freshwater, hot springs, and thermally-polluted water such as water around power plants
- Avoid water-related activities in warm freshwater during periods of high water temperature and low water levels
- Hold the nose shut or use nose clips when taking part in water-related activities in bodies of warm freshwater such as lakes, rivers, or hot springs
- Avoid digging in or stirring up the sediment while taking part in water-related activities in shallow, warm freshwater areas