Animal Waste, Water Quality and Human Health

126Animal Waste, Water Quality and Human Healthrecommended. The use of acidified water has been reported to reduce carriage ofSalmonella in the crop and caecal carriage of Campylobacter (Chaveerach et al.2004, Russell 2002). Chemical and physical treatments to reduce pathogens inthe water supply include chlorination, ozonation, frequent cleaning, raisingwater troughs, use of nipple drinkers, and screens that reduce organic solids inthe troughs. Many chemical treatments have been evaluated for their usefulnessin the control of pathogens in water sources for livestock and poultry. In cattleoperations, treatments such as acidification of water or addition of chemicals(chlorine, ozone, sodium chlorate) have had limited success because of thedifficulty of eliminating rumen content or manure from water troughs (Callawayet al. 2002). Other chemical treatments can be effective even in the presence ofmanure or rumen content in the laboratory, but so far strategies have not beenable to demonstrate a significant affect on herd prevalence rates of zoonoticenteric pathogens, and extensive investment in clean water delivery may not bewarranted (LeJeune & Wetzel 2007). In developing countries animals are oftengiven water considered unfit for human consumption, this practice obviouslyincreases the likelihood of exposure to pathogens.4.4 CONTROL POINT 2: INCREASING HOSTIMMUNITY/RESISTANCEExposure to waterborne zoonotic agents, even in high doses, does not necessarilyresult in infection. The innate or genetic ability to resist infection varies withspecies, breed and individual. In addition, resistance can be increased bymanagement practices or conferred by active or passive immunization.4.4.1 Disease resistant livestockResearch has been conducted on the breeding of pathogen-resistant animals (Adams& Templeton 1998). However, disease resistance is usually complex, involvingmany genetic loci with incremental rather than absolute levels of resistance,making it difficult to breed for resistance. However, new approaches, such aspopulation-based, whole genome-wide association studies may be moresuccessful than conventional breeding programmes in identifying and developingdisease-resistant livestock (Calenge et al. 2010; Morris 2007; Huang et al. 2011).4.4.2 VaccinationVaccination creates immunological resistance to pathogens and has beena mainstay of disease control for over a century. However, because many