Animal Waste, Water Quality and Human Health

Comparative risk analysis 369Table 10.1 Risk affecting characteristics for selected zoonotic pathogens.Potential risk factors PathogenCampylobacterjejuniE. coli(EHEC)Salmonella GiardialambliaPathogen/hostInfectivity for healthy adults (ID 50 ) a 897 750 23,600 35 35Severity of infection Mild Severe Moderate Mild ModerateHigher susceptibility for children? Yes Yes Yes Yes YesPathogen in excreta from individual animals (frequency, relative concentrations) b,gCattle (10–30 kg/day) c (H, H) (L, H) d (L, L) (M, M) (L, H)Swine (2.7–4.0 kg/day) c (H, M) (L, M) (M, M) (M, L) (L, L)Sheep (0.7–1.5 kg/day) c (H, H) (L, H) (L, L) (L, L) (L, L)Poultry (0.1–0.14 kg/day) c (H, H) (L, L) (M, M) (L, L) (L, L)Pathogen survival in environmentSurvival, days (faeces, water) e (S, S) (M, M) (L, M) (L, L) f (L, L) fCryptosporidium(parvum orhominis)a ID 50 values for these pathogens are reviewed in the Appendix (ID50 is the dose for which, on average, half of an exposed populationwill be infected).b L, M, H = Low, Medium, High. These judgements have been made in the light of the data summarized in the Appendix.c Typical faecal load from each animal group.d Marked seasonal effect; highest in summer.e S, M, L = Short, Medium, Long. The metric for “Survival” is the T 90: the time for 90% of the original population of pathogens tofbe inactivated.Marked seasonal effect, longer survival times in cooler conditions.g The model also includes the category “supershedders”. The values for this are the same as for E. coli in cattle but with the relativeconcentration of enterohaemorrhagic E. coli given an extremely high value, that is, 1000 times greater than the“average” concentration.