Identifying the Presence of Cryptosporidium, Giardia, Campylobacter and Salmonella spp. in Private Rainwater Supplies

Tank rainwater is a common source of water, particularly in rural areas of Australia. In non-metropolitan areas of Western Australia (WA), 31% of households have rainwater as a source of water. However, the health risk associated with the use of this untreated supply is still an area of uncertainty. One area of uncertainty is to what extent pathogenic microorganisms are present. The aim of the study is to assess to what extent Cryptosporidium, Giardia, Campylobacter and Salmonella spp, in particular those that cause illness in humans, are present in rainwater tanks in rural Western Australia. The method used was to take rainwater samples and tank sediments from 10 private rainwater supplies in Mount Barker, WA. The presence of Cryptosporidium and Giardia spp. was assessed in the collected samples using USEPA Method 1623. In the event of positive samples, PCR was conducted and isolates genotyped. Samples for Campylobacter and Salmonella spp. were analysed using Australian Standards and typed using serology. None of the samples tested positive for Cryptosporidium, Giardia, Campylobacter or Salmonella spp. However, thermotolerant coliforms were detected in three tanks and E.coli in two tanks. The study shows that rainwater tanks sampled were free from Cryptosporidium, Giardia, Campylobacter and Salmonella spp. The absence of these pathogens might indicate that either animals present in Mount Barker were not reservoirs for these pathogens or that the current rainwater systems and maintenance were adequate in preventing contamination. The absence might also be a result of lower temperatures and higher water volume in winter months.