What is Primary Amebic Meningoencephalitis (PAM)?
Primary Amebic Meningoencephalitis (PAM) is a rare but usually fatal brain infection caused by the free-living amoeba Naegleria fowleri. This amoeba is found naturally in warm freshwater environments like lakes, hot springs, rivers, and poorly maintained swimming pools.
PAM affects the brain and the membranes surrounding it (meninges), causing severe inflammation known as meningoencephalitis.
How Does PAM Occur?
Naegleria fowleri infects people when contaminated water enters the body through the nose, usually during activities like:
- Swimming or diving in warm freshwater lakes or rivers
- Using contaminated water for nasal irrigation or sinus rinsing
Once inside the nose, the amoeba travels along the olfactory nerve to the brain, where it causes rapid and severe damage.
Symptoms of PAM
Symptoms typically develop 1 to 9 days after exposure and progress very rapidly. They initially resemble bacterial meningitis and include:
- Severe headache
- Fever
- Nausea and vomiting
- Stiff neck
- Sensitivity to light (photophobia)
- Confusion or altered mental status
- Seizures
- Loss of balance or coordination
- Hallucinations
- Coma (in advanced stages)
Diagnosis
Diagnosing PAM is challenging because symptoms are similar to other types of meningitis, and the disease progresses quickly. Diagnosis involves:
- Examining cerebrospinal fluid (CSF) obtained by lumbar puncture to look for amoebae under a microscope
- PCR tests to detect Naegleria fowleri DNA in CSF or tissue samples
Because the disease progresses so fast, early diagnosis is critical but often difficult.
Treatment
PAM is very difficult to treat and has a high fatality rate (over 97%). However, early and aggressive treatment may save lives. Treatment options include:
- Amphotericin B: An antifungal drug used intravenously and sometimes directly into the spinal fluid
- Miltefosine: An antiparasitic drug showing promise in recent survival cases
- Other supportive measures to reduce brain swelling and control seizures
Prevention
Since PAM is contracted from water entering the nose, prevention focuses on avoiding exposure:
- Avoid swimming or diving in warm freshwater during high-risk periods (hot weather, stagnant water)
- Use nose clips or keep the head above water in lakes or hot springs
- Avoid disturbing sediment in shallow, warm freshwater areas
- Use only sterile or boiled water for nasal irrigation or sinus rinses