In the summer of 2007, there were several reported deaths from the microscopic brain-eating amoeba; the last victim of the summer, 14-year-old Aaron Evans. Doctors believe that the teen encountered the microbe a week earlier while swimming in the warm, shallow waters of Lake Havasu in Western Arizona.
Deadly Amoeba
The culprit was minute; Naegleria fowleri (nuh-GLEER-ee-uh FOWL'-erh-eye), a parasitic microorganism that enters the body through the nose and travels to the brain where it feeds on brain tissue. There is no treatment.
How Common Is N. fowleri?
Infection with Naegleria is very rare, but nearly always fatal, and so far this year there have been six U.S. cases, all young men. Twenty-three infections were documented in the U.S. between 1995 and 2004.
Cases most often occur during the dry, hot summer months, when water is warm and at low levels, the number of infections increasing during years marked by heat waves.
How N. fowleri Attacks
Infection occurs when the amoeba enters the body through the nose, invading the central nervous system by penetrating the olfactory mucosa and nasal tissues. Early infections results in necrosis (tissue death) and hemorrhaging in the olfactory bulbs. The amoeba then climbs along nerve fibers through the floor of the cranium, into the brain.
Naegleria infection can only result from exposure to the amoeba’s environment, not from person-to-person contact.
Signs and Symptoms of Naegleria Infection
This parasite attacks the human nervous system; causing primary amoebic meningoencephalitis (PAM or PAME). Initial symptoms of PAM begin 1 to 14 days after infection, and can include headache, fever, nausea, vomiting, and stiff neck.
The progressive destruction of brain tissue leads to confusion, disorientation, loss of balance, seizures, and hallucinations. Once symptoms begin, the disease quickly progresses, typically resulting in death within one week.
Where Is Naegleria Found?
Naegleria fowleri has a worldwide distribution, inhabiting lake water and soil. It is a free living amoeba typically found in warm fresh water, at temperatures ranging from 77 – 95 degrees F.
High risk habitats include:
- Warm bodies of freshwater
- Geothermal hot springs
- Warm water discharge from industrial plants
How to Reduce Your Risk
Infection usually follows water-related activities such as swimming underwater, diving, or any water sport that results in water going up the nose.
- Avoid swimming in warm freshwater, hot springs, and the thermally-polluted around power plants.
- Avoid swimming during heat waves particularly when water volume is low.
- Use nose clips when jumping or diving into bodies of warm freshwater.
- Avoid disturbing the sediment while swimming in shallow, warm freshwater areas.
Sources and Resources
To find additional resources the biology of infectious disease see the websites:
This article originally appeared in the online magazine Suite101.
