Soil is the origin for the presence of Naegleria fowleri in the thermal recreational waters

Abstract

Naegleria fowleri is found in most geothermal baths of Guadeloupe and has been responsible for the death of a 9-year-old boy who swam in one of these baths in 2008. We wanted to determine the origin for the presence of this amoeba in the water. Water samples were taken at the origin of the geothermal sources and at the arrival in the baths. After filtration, cultures were made and the number of Naegleria present was determined using the most probable number method. Soil samples collected in the proximity of the baths were also tested for the presence of thermophilic amoebae. The species identification was obtained by PCR. During three consecutive months, no Naegleria could be found at the origin of any geothermal source tested. In contrast, N. fowleri was isolated at least once in all baths at the arrival of the water, except one. Thermophilic amoebae could be found in each soil sample, especially near the baths located at a lower altitude, but N. fowleri was only isolated near two baths, which were also the baths most often contaminated with this species. So it appears that the contamination of the water with N. fowleri occurs after emerging from the geothermal source when the water runs over the soil. Therefore, it should be possible to reduce the concentration of N. fowleri in the geothermal baths of Guadeloupe to for example less than 1 N. fowleri/10 L by installing a pipeline between the geothermal sources and the baths and by preventing flooding water from entering the baths after rainfall. By taking these measures, we were able to eliminate N. fowleri from a pool located inside a reeducation clinic.

Metatranscriptomic census of active protists in soils

“…Amoebic encephalitis can also be caused by Balamuthia mandrillaris and Naegleria fowleri (Excavata, Heterolobosea) (Visvesvara et al, 1993;Schuster and Visvesvara, 2004;Visvesvara et al, 2007;Siddiqui and Ahmed Khan, 2012). The finding of related SSU rRNA sequences support recent studies showing the presence of both B. mandrillaris (Lares-Jiménez et al, 2014) and N. fowlerii in soil (Moussa et al, 2015).…”

An Optimized Most Probable Number (MPN) Method to Assess the Number of Thermophilic Free-Living Amoebae (FLA) in Water Samples

“…In Guadeloupe (French West Indies), a fatal case of PAM occurred in 2008 after a child swam in a bath fed with geothermal waters [15]. In 2013, our group revealed that thermophilic FLA (and in particular, N. fowleri) were frequently detected in these baths [12]; the contamination of the water with N. fowleri occurs after emerging from the geothermal source, when the water runs over the soil [11]. We also observed that N. fowleri was often found at low concentrations, below 22 amoebae per liter [12].…”

“…Thermophilic FLA, and in particular Naegleria sp., have been frequently detected in Guadeloupe, in soil [11] and in natural thermal water [12]. French health authorities have endorsed a rule that forbids swimming or playing sports in natural water where the concentration of N. fowleri is above 100 amoebae/L [18].…”

“…The thermophilic FLA Naegleria fowleri is frequently found in freshwater and soil [11,12], and it may cause primary amoebic meningoencephalitis (PAM), a rare but often fatal disease of the central nervous system [13]. It is generally acquired while swimming or during other recreational activities in freshwater lakes and ponds.…”

Biology and pathogenesis of Naegleria fowleri

“…N. fowleri showed 100% survival at pH ranging from 2.1 to 8.15 (220,221). Artificial heating of water by power plant discharges facilitates proliferation (222), however N. fowleri was not detected outside the reach of the thermal pollution (223), suggesting that warm discharge water should not be used for sports and entering the baths after rainfall, it is possible to reduce the concentration of amoebae in geothermal baths (232). N. fowleri has been isolated from hot springs in Yellowstone and Grand…”