Animal Waste, Water Quality and Human Health

262Animal Waste, Water Quality and Human Healthbe detected (dye uptake method) after 20 weeks and one month, respectively. Forfaecal bacteria, data from temperature exposure experiments conducted with E.coli (Rhodes & Kator 1988, Sampson et al. 2006), Campylobacter (Obiri-Dansoet al. 2001), E. coli O157:H7 (Wang & Doyle 1998) and Salmonella (Rhodes &Kator 1988) suggest these organisms are capable of surviving for days to severalweeks at temperatures above 15°C. Similarly, water temperatures below 10°C canpermit longer survival times. Thomas et al. (1999) reported that a C. jejunipopulation of greater than 4 log (initial concentration >6 log cfu/mL) could bemaintained for more than 60 days in sterile river water at a temperature of 5°C.Sampson et al. (2006) observed less than a 1 log decline from a 5 log populationof E. coli after storage for 30 days at 4°C in lake water. Information resulting fromstudies comparing the temperature-related survival of faecal indicator bacteria tobacterial faecal zoonotic pathogens has often been conflicting, with some studiesobserving prolonged survival for the pathogens (Roszak 1984, Rhodes & Kator1988) and others showing equivalent or greater survival for the indicator species(McCambridge & McMeekin 1980, Korhonen & Martikainen 1991).Sunlight intensity is another significant factor affecting the survival of faecalmicroorganisms in aquatic systems. Experiments with faecal zoonotic pathogens(Cryptosporidium, Campylobacter, Salmonella) and indicators (E. coli, faecalcoliforms, enterococci) have demonstrated that inactivation is strongly influencedby the intensity of sunlight, with significantly greater die-off rates occurringunder sunlight exposure than under dark conditions (Fujioka et al. 1981, Johnsonet al. 1997, Obiri-Danso et al. 2001, Sinton et al. 2002, King et al. 2008, Nasseret al. 2007, Schultz-Fademrecht et al. 2008). Similarly, data have been providedto suggest more rapid inactivation under solar irradiation levels more typical ofsummer as compared to winter sunlight conditions (Noble et al. 2004, Sintonet al. 2002). Studies in which the survival ability of different faecalmicroorganisms have been directly compared have demonstrated a more rapiddie-off for the bacterial species (E. coli, enterococci, Salmonella) as compared tothe faecal protozoa Giardia and Cryptosporidium (Johnson et al. 1997, Medemaet al. 1997. Nasser et al. 2007).Also important in the consideration of the exposure environment are theactivities which bring the human population in contact with the areas ofpathogen presence. In those developed countries where water resources are inabundance, the primary human activities expected to facilitate contact withlivestock-contaminated waters are recreational uses and potentially throughdrinking-water consumption.For recreational water uses, it has been proposed that activities can be separatedinto two categories as defined by the degree of water exposure expected:primary-contact and secondary-contact (WHO 2003). In primary or whole-body