Primary amoebic meningoencephalitis (patient information)
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Rim Halaby
Overview
Primary amebic meningoencephalitis (PAM), is a disease of the central nervous system. PAM is caused by Naegleria fowleri, a free-living ameba. It is a rare disease that is almost always fatal; only one person in the U.S. out of 128 has survived infection from 1962 to 2012. Signs and symptoms of Naegleria fowleri infection are clinically similar to bacterial meningitis, which lowers the chances of initially diagnosing PAM. Humans become infected when water containing Naegleria fowleri enters the nose and the ameba migrates to the brain along the olfactory nerve. People do not become infected from drinking contaminated water. Symptoms start 1-7 days (median 5 days) after swimming exposure and people die 1-12 days (median 5.3 days) after symptoms begin.
What are the symptoms of primary amoebic meningoencephalitis?
At the beginning of the infection, the symptoms include severe frontal headache, fever, nausea and vomiting. Later on, more severe symptoms develop, including stiff neck, seizures, altered mental status, hallucinations and eventually coma.
What causes primary amoebic meningoencephalitis?
Primary amebic meningoencephalitis is caused by Naegleria fowleri, a heat-loving (thermophilic), free-living ameba (single-celled microbe), commonly found around the world in warm fresh water (like lakes, rivers, and hot springs) and soil. Humans become infected when water containing Naegleria fowleri enters the nose, usually while swimming. People do not get infected by drinking contaminated water. The ameba migrates to the brain along the olfactory nerve, through a bony plate in the skull called the cribriform plate, where it reaches the brain and begins to destroy the brain tissue. The ameba has never been shown to have spread from one person to another.
Who is at highest risk?
Naegleria fowleri is naturally found in warm freshwater environments such as lakes, rivers and poorly maintained or minimally chlorinated swimming pool. Swimming behaviors associated with the increased risk of primary amoebic meningoencephalitis include diving or jumping into the water, submerging the head under water, or engaging in other water-related activities that cause water to go up the nose. PAM also disproportionately affects males and children. The reason for this distribution pattern is unclear but may reflect the types of water activities (such as diving or watersports) that might be more common among young boys.
Diagnosis
The disease is diagnosed using specific laboratory tests available in only a few laboratories in the United States. Because of the rarity of the infection and difficulty in initial detection, about 75% of diagnoses are made after the death of the patient. The laboratory tests detect Naegleria fowleri organisms, nucleic acid, or antigen in cerebrospinal fluid (CSF), biopsy, or tissue specimens
When to seek urgent medical care?
PAM is a fatal disease. Any patient with suspicious symptoms of meningoencephalitis should immediately seek medical care, especially in areas were recent cases of Naegleria fowleri are reported.
Treatment options
Yhere have been two well-documented survivors in North America: one in California and one in Mexico. Multiple patients have received treatment similar to the California survivor, including amphotericin B, miconazole/fluconazole/ketoconazole, and/or rifampin but only the patient in Mexico has survived making it difficult to determine the efficacy of the treatment regimen.
Where to find medical care for Primary amoebic meningoencephalitis?
Seek medical care in the nearest hospital.
Prevention
Personal actions to reduce the risk of primary amoebic meningoencephalitis should focus on limiting the amount of water going up the nose and lowering the chances that Naegleria fowleri may be in the water. Routine, enhanced education of the public in advance of the summer swim season might be helpful.
What to expect (Outlook/Prognosis)?
Symptoms start 1-7 days (median 5 days) after swimming exposure and people die 1-12 days (median 5.3 days) after symptoms begin.
Possible complications
PAM is a fatal disease that has very high risk of coma and death.