Naegleria fowleri in saline waters: emerging threat of primary amebic meningoencephalitis in Karachi.

Naegleria fowleri, the "brain-eating amoeba," causes primary amebic meningoencephalitis (PAM), a rapidly fatal central nervous system infection acquired mainly through nasal exposure to contaminated water. This thermophilic protozoan thrives in warm freshwater and has been increasingly reported in Karachi, Pakistan, where cases now exceed US totals over the past five decades. A recent fatality in February 2025 involved a 36-year-old woman with no recreational water exposure aside from domestic ablution, highlighting the organism's persistence in saline municipal water. The type-2 genotype in Pakistan may exhibit enhanced salinity tolerance. PAM presents with nonspecific symptoms mimicking bacterial meningitis, often leading to diagnostic delays. Rapid diagnosis via cerebrospinal fluid analysis, microscopy, and polymerase chain reaction is critical. Current treatments, including amphotericin B-based regimens and experimental combination therapies, offer limited success. Preventive strategies - public awareness, improved chlorination, and water safety measures - are imperative. Enhanced surveillance, research, and early intervention are essential to mitigate this emerging public health threat.