Animal Waste, Water Quality and Human Health

86Animal Waste, Water Quality and Human Healthhaemolytic uremic syndrome. This syndrome is characterized by haemolyticanaemia, kidney failure, coma and sometimes death (Law 2000, Rangel et al. 2005).Karmali et al. (2004) have classified EHEC into different sero-pathotypes basedon the frequency and severity of disease with which they are associated. E. coliO157:H7 is the sole member of seropathotype A because it is the mostfrequently associated with both sporadic cases and outbreaks of severe humanillness. However, even within E. coli O157:H7 differences exist among geneticlineages in the frequency and severity of disease with which they are associated.Among the three genetic lineages recognized, lineage II is primarilybovine-associated and is infrequently associated with human disease whereaslineage I strains are the most frequently isolated group associated with humanillness (Kim et al. 2001, Zhang et al. 2007). Lineage I/II contains members of aso called “hypervirulent clade” associated with higher levels of hospitalizationand haemolytic uremic syndrome than other E. coli O157:H7 genetic groups(Manning et al. 2008).E. coli O157:H7 can be passed from animal to human or human to human viaseveral routes of transmission, such as ingesting contaminated food or water, directcontact with infected animals, direct contact with an animal’s bedding or pens, andperson-to-person direct contact transmission (reviewed in Rangel et al. 2005). It isa highly infectious organism for humans: ten to several hundred bacteria can causeclinical illness (Chart 2000, Tuttle et al. 1999, Willshaw et al. 1994). Youngchildren and the elderly are the most susceptible to severe infections.3.3.1.1 Risk factors for outbreaks of E. coli O157:H7Consumption of contaminated food accounted for 52% of the 350 outbreaks and61% of the 8,598 outbreak-associated human cases in the USA from 1982 to2002, (Rangel et al. 2005). Contaminated hamburger and contaminated producewere responsible for 20% and 21% of these outbreak-associated human cases,respectively. Among produce-related foodborne illness, about half were due tocross-contamination in the kitchen, with the other half related to vegetableproduce. Contamination of produce could originate from irrigation water, animalor human wastes in fields, and water used during harvesting, processing, orshipping (Rangel et al. 2005). Waterborne transmission accounted for about18% of the outbreak-associated human cases, with the majority of theseinfections associated with contaminated drinking-water (15% of cases) and therest associated with recreational exposure to contaminated water from lakes,ponds, and pools (3% of cases). Person-to-person transmission can occur ifinfected persons, especially food handlers, do not wash their hands. Directcontact with infected animals was a minor cause of outbreaks (Rangel et al. 2005).