Environmental abiotic and biotic factors affecting the distribution and abundance ofNaegleria fowleri

Abstract

Naegleria fowleri is a free-living protozoa that resides in soil and freshwater. Human intranasal amoebae exposure through water or potentially dust particles can culminate in primary amoebic meningoencephalitis (PAM), which generally causes death. While many questions remain regarding pathogenesis, the microbial ecology of N. fowleri is even less understood. This review outlines current knowledge of the environmental abiotic and biotic factors that affect the distribution and abundance of N. fowleri. Although the impacts of some abiotic factors remain poorly investigated or inconclusive, N. fowleri appears to have a wide pH range, low salinity tolerance, and thermophilic preference. From what is known about biotic factors, the amoebae preferentially feed upon bacteria and are preyed upon by other free-living amoebae. Additional laboratory and environmental studies are needed to fill in knowledge gaps, which are crucial for surveillance and management of N. fowleri in freshwaters. As surface water temperatures increase with climate change, it is likely that this amoeba will pose a greater threat to human health, suggesting that identifying its abiotic and biotic preferences is critical to mitigating this risk.

Case of Primary Amebic Meningoencephalitis Associated with Surfing at an Artificial Surf Venue: Environmental Investigation

“…Although rare, multiple N. fowleri infections have been associated with exposure to artificial freshwater venues, like the surf venue or cable park ponds (Table 2). 3,27,28 Disinfection or treatment of natural freshwater bodies due to N. fowleri is not recommended for practical and ecological reasons, but given the previous cases associated with artificial water sport venues (Table 2), venues, like the cable park, could consider signage informing patrons about the presence or risk of N. fowleri, particularly in seasons when the water is warmer. No PAM cases have been associated with adequately treated recreational water venues (e.g., pools and splash pads).…”

“…2 N. fowleri is well documented in soil and, in some instances, can contaminate nearby waters through runoff. 3 Free-living amebae (FLA) are also ubiquitous in biofilms, which provide a source of nutrients as well as protection from disinfectants. 4,5 Nasal exposures to the FLA, N. fowleri, associated with recreational water typically occur during activities that can force water containing the ameba into the nasal cavity (e.g., diving and jumping in water) and the ameba subsequently migrate to the brain.…”

“…N. fowleri is well documented in soil and, in some instances, can contaminate nearby waters through runoff . Free-living amebae (FLA) are also ubiquitous in biofilms, which provide a source of nutrients as well as protection from disinfectants. , Nasal exposures to the FLA, N.…”

“…fowleri through recreational water activities (e.g., swimming, diving, and water sports) in lakes, ponds, reservoirs, canals, and to a lesser extent inadequately disinfected pools. , Surfing had not previously been documented as a risk for exposure, even though the action of surfing frequently forces water up the surfers’ nose because until recently, surfing primarily occurred in the ocean, and N. fowleri has a low tolerance to saltwater …”

A Fluorometric Assay for the In Vitro Evaluation of Activity against Naegleria fowleri Cysts

“…The trophozoites can turn into flagellate stage in aqueous environments with lack of nutrients ( 10 , 11 ) or when the ionic concentration of the media changes ( 12 ). The cystSt of N. fowleri can be found under unfavorable conditions, namely high temperatures, low pH-environments, or high salinity levels ( 13 ).…”