Animal Waste, Water Quality and Human Health

Zoonotic waterborne pathogen loads in livestock 85Frequency of samples5004504003503002502001501005001-500 501-1000Arimethic mean intensity~10,700 cysts/g faeces1001-50005001-10,00010,001-50,00050,001-100,000Giardia duodenalis (cysts/gram faeces)100,001-500,000>500,000Figure 3.2 Frequency distribution of the intensity of Giardia duodenalis cyst in fresh faecal patscollected from feedlot pens from central and western USA, adapted from Hoar et al. 2009.3.3 WATERBORNE ZOONOTIC BACTERIA3.3.1 E. coli O157:H7Although most E. coli strains are harmless and live in the intestines of healthyhumans and animals, certain so called pathogroups of the organism consist ofstrains from specific serotypes that are associated with gastrointestinal andextra-intestinal infections (e.g. septicaemia, mastitis and urinary tract infections)in both humans and animals. Many of the members of these pathogroups sharevirulence attributes such as those necessary for gastrointestinal colonization.These factors include adhesins that allow them to attach to host-specific receptorsin the intestine. In contrast to the other pathogroups, enterohaemorrhagic E. coli(EHEC) usually occur as part of the normal flora of the intestinal tract ofruminants and only cause disease when they are accidentally ingested byhumans. EHEC produce one or more antigenic types of protein toxins, closelyrelated to Shiga toxin, that cause cell death and apoptosis followingreceptor-mediated cell up-take (Karmali et al. 2009, Law 2000). E. coli O157:H7and other EHEC (e.g., serotypes O26, O103, and O111) are associated with aspectrum of gastrointestinal illness in humans from simple diarrhoea tohaemorrhagic colitis which is characterized by bloody diarrhoea. Occasionally,passage of toxins produced by the organism into the blood stream following thegastrointestinal form of the infection, result in a systemic illness called the