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

Abstract

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 × 10 to 3.6 × 10 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 × 10 to 7.8 × 10 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.

Opportunistic Premise Plumbing Pathogens. A Potential Health Risk in Water Mist Systems Used as a Cooling Intervention

“…This study did not detect any M. avium nor N. fowleri in any samples, water (30), biofilms (30) or bioaerosols (30). Although not isolated in any samples, the potential presence of M. avium and N. fowleri in WMS cannot be completely ruled out, since studies of similar systems have demonstrated that this pathogen can regrow in premise plumbing [ 29 , 49 , 50 ]. The low sample volumes collected (250 mL) could have resulted in the extracted gene copies being less than the qPCR method’s limit of detection.…”

Opportunistic Premise Plumbing Pathogens. A Potential Health Risk in Water Mist Systems Used as a Cooling Intervention

“…Several studies that have investigated the occurrence of OPPPs in premise plumbing systems such as domestic water taps, hospital faucets and showers have reported varying results ranging from zero detection of M. avium and N. fowleri in domestic tap water [27], to 15 % (n = 134) occurrence of N. fowleri in roof harvested rainwater tanks in Australia [51] and 13.5 % (n = 656) mean abundance of Mycobacterium species in showerhead biofilm samples from Europe and the USA [52]. Our investigation did not detect any M. avium nor N fowleri in all samples, water (30), biofilms (30) and bioaerosols (30).…”

Microbiological Health Risk Assessment of Water Conservation Strategies: A Case Study in Amsterdam

“…Microbial contaminants can be introduced from the air, the surface of the catchment, the conveyance system, and in the storage [ 29 ]. Various pathogens have been identified in harvested rainwater such as E. coli , Salmonella spp., Giardia lamblia, Legionella spp., Campylobacter jejunii, Aeromonas spp., Pseudomonas spp., Mycobacterium avium complex (MAC), and Naegleria fowleri [ 13 , 21 , 30 , 31 ]. Even though viruses may also present in rainwater, we could not find enough data regarding their concentration in rainwater, thus viruses are not included in this study.…”