Animal Waste, Water Quality and Human Health

Exposure interventions 303examples of how recognition of a problem has resulted in initiatives that have ledto concrete improvements.Case Study 1: Cryptosporidiosis and unfiltered drinking water, Scotland, UK 1BackgroundCryptosporidiosis may be caused by multiple species of the genus Cryptosporidium;the most important human pathogens being Crypto. hominis and Crypto.parvum. Crypto. hominis infection is mainly restricted to humans but Crypto. parvuminfects a variety of mammals (especially neonatal cattle and sheep) as well as humans.Persons at risk of infection include those participating in recreational activities(swimming as well as the drinking of unfiltered water), and travelers to endemic regions.ProblemIn Scotland, 600–900 laboratory-confirmed cases of cryptosporidiosis are reported toHealth Protection Scotland (HPS) each year. Infection is frequently disseminated byperson-to-person transmission, by animal reservoirs such as sheep and cattle, andindirectly through the environment (particularly by water). Indeed, drinking-watercontaminated by oocysts is an internationally recognized risk factor for human disease(McAnulty et al. 2000; Goh et al. 2005, Hunter & Thompson 2005). The disease stateis typically associated with bloating, abdominal pain, nausea and prolonged diarrhoea.While the illness is normally self-limiting, a recent study has shown it can lead toserious health sequelae and may even be fatal (Hunter et al. 2004; Caccio et al. 2005).Within the past ten years, two large outbreaks of waterborne cryptosporidiosis haveoccurred in Scotland: 90 confirmed cases in Glasgow in 2000 associated with unfilteredLoch Katrine water and 140 cases in Aberdeen in 2002 associated with suboptimalfiltration of River Dee water. Previous evidence has suggested an association betweenconsumption of unfiltered water from Loch Lomond and cryptosporidiosis (Smithet al. 1993). Loch Lomond supplies water to ∼34% of the population of central Scotland.Improvement InitiativeLoch Lomond. Before November 1999, Loch Lomond water was only micro-strained(only particles >23 µm were filtered out) and disinfected with chlorine, and the risk oftransmitting Cryptosporidium spp. oocysts (4–6 µm) to consumers of this water wasrelatively high. In November 1999, enhanced physical treatment (coagulation and1Contributed by Kevin G.J. Pollock, Colin N. Ramsay, and David Young (Health ProtectionScotland).