Animal Waste, Water Quality and Human Health

the cause of a variety of food- and waterborne outbreaks of human illness over thepast twenty years. One of the largest of these occurred in Swaziland where cattlemanure was thought to be the source of more than 40,000 cases of waterborneinfection with the organism (Effler et al. 2001). This underlines the need tocarefully handle and dispose of stored manure and to encourage proper grazingmanagement so as to reduce this route of transmission to humans (reviewed inGuan & Holley, 2003; Rangel et al. 2005). In addition to cattle and sheep, E. coliO157:H7 has been isolated from a wide variety of animals, including dogs,horses, white-tailed deer, elk, raccoon, various species of birds such as starlings,gulls, and geese, feral pig, flies, and others (reviewed in Renter & Sargeant 2002and Pedersen & Clark 2007). However, it is not clear if all of these wildlifespecies are reservoirs of this pathogen or simply act as passive carriers of theorganism derived from ruminant excreta. Therefore, we do not have a clearunderstanding of how wildlife populations in agricultural or rural watershedsparticipate in the environmental cycling of this pathogen (Pedersen & Clark 2007).3.3.2 CampylobacterZoonotic waterborne pathogen loads in livestock 89Campylobacter spp. are the leading cause of human bacterial gastroenteritis in thedeveloped world (Friedman et al. 2004). Campylobacteriosis is characterized byacute gastroenteritis and is occasionally associated with the Guillain-BarréSyndrome (a demyelinating polyneuropathy characterized by ascendingparalysis) (Aspinall et al. 1994). There are several species of Campylobacterthat have been associated with infections in humans; however, Campy. jejuniaccounts for approximately 90% of human cases, with most of the remainderassociated with Campy. coli (Friedman et al. 2004; Humphrey et al. 2007). Asfew as 500 to 800 organisms appear sufficient to cause clinical illness in humans(Robinson 1981, Black et al. 1988). Most cases of campylobacteriosis (ca. 80%)are thought to be foodborne in origin. The most important risk factor forsporadic campylobacteriosis is the consumption of undercooked poultry. Otherrisk factors include the consumption of raw milk (Teunis et al. 2005), exposureto pets and farm animals, especially when they have diarrhoea, and drinkinguntreated surface water (Friedman et al. 2004; Humphrey et al. 2007). Directhuman-to-human transmission is uncommon (Tauxe 1992; Altekruse et al.1994, Franco & Williams 1994, Adak et al. 1995), but direct animal-to-humantransmission via contact with calves has been implicated in some cases (Smith,1984; Friedman et al. 2004; Belongia et al. 2003). Foodborne cases are typicallysporadic in nature and outbreaks associated with food sources are rare (Meadet al. 1999, Friedman et al. 2004). Seasonal variation has been noted in theprevalence of campylobacteriosis in temperate regions in both the southern and