Animal Waste, Water Quality and Human Health

Zoonotic waterborne pathogen loads in livestock 95bovine manure slurries has been shown to be 30 days compared with 90 days forE. coli O157:H7 and Salm. enterica Typhimurium (Nicholson et al. 2005).Similarly, Sinton et al. (2007) reported that Campylobacter was inactivated after6.2 days in faecal pats compared with 38 days for Salm. enterica.Lejeune et al. (2001a) reported isolation of Salmonella spp. from 2/235 (0.8%)and E.coli O157 from 6/473 (1.3%) water-troughs from cattle operations in theUSA. Laboratory studies have shown that E. coli O157 can survive for 245 daysin simulated water-trough sediments (Lejeune et al. 2001b). There is evidencethat predation by protozoa reduces populations of “planktonic” enteric bacteria insurface waters. For example E. coli O157 populations decline in river waterfrom 10 6 CFU/ml to undetectable levels after 27 days (Maule 2000). Wang andDoyle (1998) reported that E. coli O157 population declines are slowest infiltered lake water and at lower temperatures. Campy. jejuni populations declinemore rapidly in surface water (7 to 15 days) than those of E. coli; however, thedecline is also slower at lower temperatures (Korhonen & Martikainen 1991).Survival of E. coli O157 and other bacterial pathogens in sediments and onsurfaces is thought to be prolonged as a result of biofilm formation.3.4 METHODOLOGICAL CONCERNS REGARDINGMONITORING PATHOGEN LOADSThere are several methodological concerns regarding sampling strategies andmonitoring methods for characterizing livestock pathogen loads. Valid andprecise quantitative estimates need to be generated for the daily faecalproduction per animal, the prevalence or incidence of pathogen shedding, andthe intensity of pathogens excreted by infected animals. Calculating the loadingrate facilitates a more accurate match between expected pathogen loads for alivestock production system and the efficacy of the intervention strategy forattenuating the pathogen load (Tate et al. 2004, Koelsch et. al. 2006). Currentestimates for faecal production often rely on a single value to represent all adultsor all juvenile livestock (Table 3.2), but using a percentage of body weight toestimate faecal production may allow a more accurate match to the group’sweight and age composition (Atwill et al. 2004). One of the most importantissues is that most of the animal infection literature is dominated by prevalencedata which do not account for the up to 10 7 difference in shedding intensitybetween age classes, clinical status of animals, or different host species. Forexample, if 50% percent of animal group A sheds 10 2 Salmonella per day and1% of animal group B sheds 10 6 Salmonella per day, on the basis of prevalencegroup A would be the priority host, but species B sheds 200-fold higher