Inactivation of Naegleria fowleri by chlorine and ultraviolet light

Naegleria fowleri is a free-living protozoa that causes the fatal disease primary amoebic meningoencephalitis; the only cases associated with drinking water have occurred in Australia and Arizona. A recent study found N. fowleri in 8% (n = 143) of all municipal untreated drinking water wells tested. The C × T (concentration × exposure time) values for chlorine inactivation of N. fowleri trophozoites and cysts at an average disinfectant concentration of 1 mg/L were determined using the efficiency factor Hom model. The estimated C × T values for N. fowleri cysts are comparable to the published values for Giardia cysts, but are lower than those for Cryptosporidium oocysts. In this study, the ultraviolet light dosage required for the inactivation of the cyst stage of N. fowleri was determined to be greater than that of Cryptosporidium oocysts but less than that of Acanthamoeba cysts.