Primary amoebic meningoencephalitis
| Naegleriasis | |
|---|---|
| Synonyms | primary amoebic meningoencephalitis (PAM), amebic encephalitis, naegleria infection, amoebic meningitis |
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| Histopathology of primary amebic meningoencephalitis due to Naegleria fowleri. Direct fluorescent antibody stain. | |
| Pronunciation | |
| Classification and external resources | |
| Specialty | Infectious disease |
| ICD-10 | A06.6, B60.2 |
| ICD-9-CM | 136.2 |
Naegleriasis (also known as primary amoebic meningoencephalitis) is an infection of the brain by the free-living unicellular Naegleria fowleri.
N. fowleri is typically found in warm bodies of fresh water, such as ponds, lakes, rivers, and hot springs. It is also found in soil, poorly maintained municipal water supplies, water heaters, near warm-water discharges of industrial plants, and in poorly chlorinated, or unchlorinated swimming pools, in an amoeboid or temporary flagellate stage. There is no evidence of it living in salt water.
Although infection occurs rarely, it nearly always results in death, with a case fatality rate greater than 95%.
Onset symptoms of infection can start from one to seven days after exposure. Initial symptoms include changes in taste and smell, headache, fever, nausea, vomiting, and a stiff neck. Secondary symptoms include confusion, hallucinations, lack of attention, ataxia, and seizures. After the start of symptoms, the disease progresses rapidly over three to seven days, with death occurring usually from seven to fourteen days later, although it can take longer. In 2013, a man in Taiwan died twenty-five days after being infected by Naegleria fowleri.
It affects healthy children or young adults with no prior history of immune compromise who have recently been exposed to bodies of fresh water.
N. fowleri invades the central nervous system via the nose, specifically through the olfactory mucosa of the nasal tissues. This usually occurs as the result of the introduction of water that has been contaminated with N. fowleri into the nose during activities such as swimming, bathing, or nasal irrigation.
The amoeba follows the olfactory nerve fibers through the cribriform plate of the ethmoid bone into the skull. There, it migrates to the olfactory bulbs and subsequently other regions of the brain, where it feeds on the nerve tissue, resulting in significant necrosis and bleeding.
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