Roof-harvested rainwater has long been considered an alternative source of water in water-scarce regions worldwide. However, concerns regarding the microbiological and chemical quality of roof-harvested rainwater have been raised due to the potential presence of bacterial and protozoan pathogens. A recent study aimed to shed light on this issue by investigating the occurrence of pathogenic amoeba in roof-harvested rainwater tank samples from Southeast Queensland, Australia, and the Kleinmond Housing Scheme in Kleinmond, South Africa. The research, conducted by a team of scientists from Stellenbosch University, Drexel University, and CSIRO Land and Water, focused on Naegleria fowleri, a pathogenic amoeba known for its potential health risks and associations with opportunistic pathogens. The team collected a total of 134 roof-harvested rainwater tank samples from Australia and 80 samples from South Africa. To assess the concentration of Naegleria fowleri, the researchers employed quantitative PCR (qPCR) assays. The study found that 11.2% of the water samples from Australia (15 out of 134) and 18.8% of the South African tank water samples (15 out of 80) were positive for Naegleria fowleri. The concentrations of Naegleria fowleri gene copies per 100 mL of water ranged from 1.7 × 10² to 3.6 × 10⁴ in Australia and from 2.1 × 10¹ to 7.8 × 10⁴ in South Africa. These findings raise concerns about the prevalence of Naegleria fowleri in roof-harvested rainwater and emphasize the need for further development of dose-response models for Naegleria fowleri and a quantitative microbial risk assessment. These findings also provide valuable insights into the potential health hazards associated with using roof-harvested rainwater as a water source in water-scarce regions. Researchers and policymakers can utilize this information to develop effective mitigation strategies and ensure the safety of people relying on alternative water sources.

Reference

Waso, M., Dobrowsky, P. H., Hamilton, K. A., Puzon, G., Miller, H., Khan, W., & Ahmed, W. (2018). Abundance of Naegleria fowleri in roof-harvested rainwater tank samples from two continents. Environmental Science and Pollution Research, 25, 5700-5710. DOI: 10.1007/s11356-017-0870-9.