Operational management of Naegleria spp. in drinking water supplies in Western Australia

Trolio, R.; Bath, Andrew; Gordon, Cameron; Walker, Ruth H.; Wyber, Andrew

doi:10.2166/ws.2008.063

Cited by 16 publications

(16 citation statements)

References 6 publications

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“…In a free-chlorine burn, the secondary disinfectant is switched temporarily from chloramines to free chlorine (at concentrations above breakpoint concentration). Trolio et al (2008) reviewed the conditions under which N. fowleri tend to be found in drinking water supplies in Western Australia and the operational steps used to control or mitigate N. fowleri. Application of those techniques for nitrification control could affect N. fowleri in distribution systems.…”

Section: N Fowleri Management In Drinking Water Production and Distrmentioning

confidence: 99%

“…For example, flushing could mobilize N. fowleri resident in sediments; pH adjustment could change the susceptibility of N. fowleri to secondary disinfection; and free-chlorine burns could result in reduced disinfectant penetration into biofilms. Trolio et al (2008) reviewed the conditions under which N. fowleri tend to be found in drinking water supplies in Western Australia and the operational steps used to control or mitigate N. fowleri. Surface and groundwater sources for which the water temperature is greater than 25°C for four months per year are classified as at high risk for Naegleria contamination.…”

Section: N Fowleri Management In Drinking Water Production and Distrmentioning

confidence: 99%

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Naegleria fowleri: An emerging drinking water pathogen

2014

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Naegleria fowleri (N. fowleri) is a free‐living, trophic amoeba that is nearly ubiquitous in the environment and can be present in high numbers in warm waters. It is the causative agent of primary amoebic meningoencephalitis (PAM), a rare but particularly lethal disease with a very low survival incidence. Although N. fowleri was isolated from drinking water supplies in Australia in the 1980s, it was not considered a drinking water threat in the United States until recent cases were associated with a groundwater system in Arizona and surface water systems in Louisiana. N. fowleri in drinking water treatment and distribution systems can be managed using disinfectant concentrations typically encountered in well‐run plants although nitrification and attendant low disinfectant residuals may pose a challenge for some systems. The greatest challenge for N. fowleri control is in premise plumbing systems where conditions are largely outside the control of utilities, residuals might be low or nonexistent, and where water temperatures could be high enough to support rapid growth of the amoebae. This article reviews published studies describing the environmental occurrence, survival, pathogenicity, and disinfection of N. fowleri. In addition, this article provides information about this little known and poorly understood parasite with respect to its occurrence in the environment; how the amoeba amplifies in water systems such that it can cause infection; how N. fowleri has been successfully controlled for decades in water systems through treatment and distribution system management in Australia; and the knowledge gaps and information needed to address N. fowleri as an emerging pathogen in US water supplies.

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Section: N Fowleri Management In Drinking Water Production and Distrmentioning

confidence: 99%

Section: N Fowleri Management In Drinking Water Production and Distrmentioning

confidence: 99%

Naegleria fowleri: An emerging drinking water pathogen

2014

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“…Operational control and management of Naegleria based on the application of contact times greater than 30 mg Cl 2 min l −1 and maintenance of a free chlorine residual of 0·2 mg l −1 in the end section of water distribution systems was tried in Australia and has proved to be effective (Trolio et al . ). The stronger resistance of cysts to oxidant disinfection is due to the structure and composition of the cyst wall that is more resilient than that of the trophozoïtes (Visvesvara et al .…”

Section: Discussionmentioning

confidence: 97%

“…Recent findings have reported Ct values of 6 mg Cl 2 min l À1 for N. fowleri trophozoites and 31 mg Cl 2 min l À1 for cysts, leading to 3-log inactivation of the pathogenic amoeba with chlorine (Gerba et al 2009;Sarkar and Gerba 2012). Operational control and management of Naegleria based on the application of contact times greater than 30 mg Cl 2 min l À1 and maintenance of a free chlorine residual of 0Á2 mg l À1 in the end section of water distribution systems was tried in Australia and has proved to be effective (Trolio et al 2008). The stronger resistance of cysts to oxidant disinfection is due to the structure and composition of the cyst wall that is more resilient than that of the trophozo€ ıtes (Visvesvara et al 2007;Johnston et al 2009).…”

Section: Discussionmentioning

confidence: 99%

Biocidal efficacy of monochloramine against planktonic and biofilm-associated Naegleria fowleri cells

Goudot

Herbelin²,

Mathieu

et al. 2014

J Appl Microbiol

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Aims: Free-living amoebae (FLA) in aqueous systems are a problem for water network managers and health authorities because some are pathogenic, such as Naegleria fowleri, and they have also been reported to operate as reservoirs and vectors of several pathogenic bacteria. Therefore, to better control the occurrence of such amoebae, we evaluate the efficacy of monochloramine against planktonic forms (trophozoites and cysts) and also biofilm-associated cells of N. fowleri as FLA are often associated with biofilms. Methods and Results: From a freshwater biofilm growing in a pilot reactor and inoculated with N. fowleri, we obtained Ct values ranging from 4 to 17 mg Cl 2 min l À1 at 25°C and pH 8Á2 on both planktonic and biofilm associated cells. In addition, the inactivation pattern of biofilm associated was intermediate between those of trophozo€ ıtes and cysts. Conclusions:The monochloramine efficiency varies with the life stage of N. fowleri (trophozo€ ıte, cyst, and biofilm-associated). The sensitivity to disinfectant of amoeba, that is, trophozo€ ıtes and cysts, in the biofilm life stage is as high as that of their planktonic cyst form. Significance and Impact of the Study: This study gives Ct values for cysts and biofilm-associated N. fowleri. This may impact on water treatment strategies against amoebae and should be considered when controlling N. fowleri in manmade water systems such as cooling towers or hot water systems.

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“…26,30,31,36,37,39−41 These three factors could explain why N. fowleri is predominantly isolated from water samples downstream of treatment processes. 5,10,42 Furthermore, the ever increasing death toll due to PAM in Karachi, Pakistan, is likely the result of inconsistent free chlorine concentrations throughout the DWDS allowing N. fowleri to survive and thrive within the biofilm throughout the network and into household plumming and water storage tanks.…”

Section: Discussionmentioning

confidence: 99%

Reduced Efficiency of Chlorine Disinfection of Naegleria fowleri in a Drinking Water Distribution Biofilm

Miller

Wylie

Déjean

et al. 2015

Environ. Sci. Technol.

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Naegleria fowleri associated with biofilm and biological demand water (organic matter suspended in water that consumes disinfectants) sourced from operational drinking water distribution systems (DWDSs) had significantly increased resistance to chlorine disinfection. N. fowleri survived intermittent chlorine dosing of 0.6 mg/L for 7 days in a mixed biofilm from field and laboratory-cultured Escherichia coli strains. However, N. fowleri associated with an attached drinking water distribution biofilm survived more than 30 times (20 mg/L for 3 h) the recommended concentration of chlorine for drinking water. N. fowleri showed considerably more resistance to chlorine when associated with a real field biofilm compared to the mixed laboratory biofilm. This increased resistance is likely due to not only the consumption of disinfectants by the biofilm and the reduced disinfectant penetration into the biofilm but also the composition and microbial community of the biofilm itself. The increased diversity of the field biofilm community likely increased N. fowleri's resistance to chlorine disinfection compared to that of the laboratory-cultured biofilm. Previous research has been conducted in only laboratory scale models of DWDSs and laboratory-cultured biofilms. To the best of our knowledge, this is the first study demonstrating how N. fowleri can persist in a field drinking water distribution biofilm despite chlorination.

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Operational management of Naegleria spp. in drinking water supplies in Western Australia

Cited by 16 publications

References 6 publications

Naegleria fowleri: An emerging drinking water pathogen

Naegleria fowleri: An emerging drinking water pathogen

Biocidal efficacy of monochloramine against planktonic and biofilm-associated Naegleria fowleri cells

Reduced Efficiency of Chlorine Disinfection of Naegleria fowleri in a Drinking Water Distribution Biofilm

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