Animal Waste, Water Quality and Human Health

130Animal Waste, Water Quality and Human HealthE. coli O157:H7 has been associated with large outbreaks of human infection andsporadic infections in almost all regions of the world (Cooley et al. 2007, Bell et al.1994, Yukioka & Kurita 1997, Effler et al. 2001, Machino et al. 1999, Dundas et al.2001). In the USA, Canada and the United Kingdom regional differences in rates ofE. coli O157:H7 infection have been noted (Innocent et al. 2005, Gould et al. 2009,Waters et al. 2004, Michel et al. 1999) ranging from 10 cases per 100,000population per year. E. coli O157:H7 infections have been associated with a varietyof food products including ground beef, unpasteurized dairy products, raw fieldvegetables, radish sprouts and fruit juices (Erickson & Doyle 2007). In addition,outbreaks of human infections have been associated with recreational anddrinking-water. In Walkerton, Ontario, Canada contamination of well watercontributing to the town water supply and a failure in the chlorination system resultedin over 2300 illnesses, 28 cases of HUS and 7 deaths (Auld et al. 2004). In Swazilandan estimated 42,000 individuals suffered from E. coli O157 infections as a result ofcontaminated river water (Effler et al. 2001).Cattle and E. coli O157:H7 infections in humansThe primary source of the pathogen in most of these food- and environment-associateddisease cases is thought to have been ruminant faeces. Cattle and other ruminants arethought to be natural hosts of E. coli O157:H7; however, they are not associated withclinical disease in this animal reservoir. The linkage between E. coli O157:H7infection in cattle and humans is based on a number of lines of evidence: (1) Eatingof undercooked ground beef and unpasteurized milk are risk factors for acquiring E.coli O157:H7 infections, (2) E. coli O157 infections occur more frequently in regionswith high cattle density (Michel et al. 1999), (3) Argentina has the highest rate ofHUS and the highest beef consumption per capita, and cultural practices such asfeeding raw beef juice (“jugo de carne”) to infants have been associated with HUS(Rivas et al. 2008), and (4) isolates of the pathogen from outbreaks of human illnesshave been shown to share the same molecular fingerprint as epidemiologically linkedcattle isolates (Louie et al. 1999).Control of E. coli O157:H7 in cattleA significant amount of attention has been focused on control of E. coli O157:H7 inslaughter houses, beef processing plants, restaurants and at home by bothgovernments and industry in a number of developed economies (Gannon 1999). Thisarose from clear evidence that E. coli O157:H7 from ground beef was associated withhuman disease, threats of litigation and trade restrictions, loss of consumer confidenceand significant costs to industry associated with the recall of millions of tons ofcontaminated ground beef. Measures adopted to control the pathogen included the