Animal Waste, Water Quality and Human Health

304Animal Waste, Water Quality and Human Healthrapid gravity filtration), designed in part to reduce the number of oocysts, wasintroduced. This treatment of the Loch Lomond supply was expected to reduce theoocyst load in the final supply. To determine risk factors for cryptosporidiosis,including in drinking-water, data were analysed of laboratory-confirmed cases ofcryptosporidiosis collected from 1997 through 2003. An association between theincidence of cryptosporidiosis and unfiltered drinking-water supplied to homes wasidentified. Data strongly suggested that drinking unfiltered tap water from LochLomond transmitted Cryptosporidium spp. at the population level. The associationsupports the view that adding a filtration system to minimally treated water cansubstantially reduce the number of confirmed cryptosporidiosis cases.Loch Katrine. Water originating from Loch Katrine is used to supply part of thepopulation of Central Scotland. Prior to September 2007, this water was unfilteredand therefore posed a relatively high risk of transmitting viable Cryptosporidiumoocysts to consumers. After September 2007, rapid gravity filtration treatment wasintroduced, designed to reduce the number of oocysts passing into the finaldistribution supply. In theory, if a proportion of the sporadic cases of illness wereattributable to drinking unfiltered Loch Katrine water, then there should be areduction in the number of such cases following the introduction of filtration treatment.Lessons for the futureThe association of outbreaks linked to drinking inadequately treated tap water supportsthe view that adding a filtration system to minimally treated water can substantiallyreduce the number of confirmed cryptosporidiosis cases.Case Study 2: Bathing Water Quality: UV light disinfection system to reducebeach postings, Fanshawe Beach, Ontario, CA 2BackgroundIn the 1950s the Fanshawe Dam was built on the Thames River, Ontario, Canada tocontrol flooding in the watershed. The Upper Thames River Conservation Authority(UTRCA) subsequently developed the surrounding land and reservoir including aswimming area and beach for outdoor recreational use. Low flow and high nutrientloads from urban and rural areas often resulted in unacceptable levels of E. coli insurface water.2Contributed by Steven Musclow (Upper Thames River Conservation Authority) and GordonYasvinski (Health Canada).