Question
Primary amoebic meningoencephalitis
Answer
Primary Amoebic Meningoencephalitis (PAM) is a rare but almost universally fatal, rapidly progressive CNS infection caused by Naegleria fowleri, a thermophilic free-living amoeba found in warm freshwater.
Transmission: contaminated warm freshwater enters the nose (typically during swimming, diving), and the amoeba migrates along the olfactory nerve, crossing the cribriform plate, to directly invade the brain.
Clinical course: occurs in previously healthy individuals (unlike Acanthamoeba GAE, which affects the immunocompromised); onset is abrupt — severe headache, fever, neck stiffness, rapid progression to altered consciousness, seizures, and death — typically within 3–7 days, case fatality >95%.
Laboratory diagnosis: CSF shows features resembling bacterial meningitis (neutrophilic pleocytosis, raised protein, low glucose) but with motile amoebae visible on wet-mount microscopy of fresh, unrefrigerated CSF; PCR for confirmation.
Treatment: amphotericin B (IV and intrathecal) combined with other agents (miltefosine, azithromycin); prognosis remains very poor.
Prevention: avoiding nasal water exposure in warm freshwater, nose clips while swimming, proper pool chlorination.