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Abundance of Naegleria fowleri in roof-harvested rainwater tank samples from two continents


Roof-harvested rainwater (RHRW) has been used as an alternative source of water in water scarce regions of many countries. The microbiological and chemical quality of RHRW has been questioned due to the presence of bacterial and protozoan pathogens. However, information on the occurrence of pathogenic amoeba in RHRW tank samples is needed due to their health risk potential and known associations with opportunistic pathogens. Therefore, this study aims to determine the quantitative occurrence of Naegleria fowleri in RHRW tank samples from Southeast Queensland (SEQ), Australia (AU), and the Kleinmond Housing Scheme located in Kleinmond, South Africa (SA). In all, 134 and 80 RHRW tank samples were collected from SEQ, and the Kleinmond Housing Scheme, Western Cape, SA, respectively. Quantitative PCR (qPCR) assays were used to measure the concentrations of N. fowleri, and culture-based methods were used to measure fecal indicator bacteria (FIB) Escherichia coli (E. coli) and Enterococcus spp. Of the 134 tank water samples tested from AU, 69 and 62.7% were positive for E. coli, and Enterococcus spp., respectively. For the SA tank water samples, FIB analysis was conducted for samples SA-T41 to SA-T80 (n = 40). Of the 40 samples analyzed from SA, 95 and 35% were positive for E. coli and Enterococcus spp., respectively. Of the 134 water samples tested in AU, 15 (11.2%) water samples were positive for N. fowleri, and the concentrations ranged from 1.7 × 102 to 3.6 × 104 gene copies per 100 mL of water. Of the 80 SA tank water samples screened for N. fowleri, 15 (18.8%) tank water samples were positive for N. fowleri and the concentrations ranged from 2.1 × 101 to 7.8 × 104 gene copies per 100 mL of tank water. The prevalence of N. fowleri in RHRW tank samples from AU and SA thus warrants further development of dose-response models for N. fowleri and a quantitative microbial risk assessment (QMRA) to inform and prioritize strategies for reducing associated public health risks.

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This research was undertaken and funded as part of a Fulbright-CSIRO Postgraduate Scholarship sponsored by the CSIRO Land and Water Flagship. We sincerely thank the residents of SEQ for providing access to their rainwater tanks and for their feedback on the survey. We also thank Ms. Kylie Smith and Andrew Palmer for aiding in sample collection. The South African authors would also like to thank the Water Research Commission (WRC Project K5/2368//3) and the National Research Foundation of South Africa (Grant number: 90320) for funding this project. Opinions expressed and conclusions arrived at are those of the authors and not necessarily to be attributed to the National Research Foundation (South Africa).

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Correspondence to Warish Ahmed.

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Waso, M., Dobrowsky, P.H., Hamilton, K.A. et al. Abundance of Naegleria fowleri in roof-harvested rainwater tank samples from two continents. Environ Sci Pollut Res 25, 5700–5710 (2018). https://doi.org/10.1007/s11356-017-0870-9

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  • Naegleria fowleri
  • Roof-harvested rainwater
  • Fecal indicator bacteria
  • Health risks