Animal Waste, Water Quality and Human Health

142Animal Waste, Water Quality and Human Healthbefore have such large populations been kept in such small spaces requiring suchcomplex management. While some believe that the apex of intensification has beenachieved and the future will see a shift to small-scale organic local production, itmay be more realistic to hypothesize that growing populations and demand foranimal protein can only lead to further intensification and industrialisation(Steinfeld et al. 2006). Technological and methodological advances haveundoubted potential to revolutionise control of waterborne zoonoses at farmlevel. Molecular epidemiology is increasing our understanding of transmissionof pathogens and providing unexpected insights which can lead to new controlstrategies. Genomic studies offer the opportunity to scan for potential vaccineantigens, and engineer new vaccines. Genetic modification, if acceptable to thepublic, could be used to introduce disease resistance to livestock. Risk-basedapproaches and disease modelling bring new ways of understanding andmanaging harm associated with pathogens. The related concepts of “One World,One Health, One Medicine” and “EcoHealth” which view animal, human andecosystem health as inextricably linked, may likewise herald a radical rethink ofthe prevention and control of zoonoses (Zinstag et al. 2007). Innovation will beundoubtedly needed in the next decades as the effects of climate change areincreasingly felt. This is likely to affect pathogen loads at farm level throughmultiple pathways, as yet poorly understood, but including: pathogen survival inthe environment, livestock nutrition, livestock susceptibility, breeds of livestockkept, and farming systems (Thornton et al. 2008)4.8 CONCLUSIONSThe idea of risk pathways and the concept of “source to tap” offer at once arationale for pushing pathogen control down the value chain and a method foridentifying the points where control can be applied. In this Chapter we identifyfour sequential key control points: minimising exposure of livestock topathogens; increasing livestock resistance to infection; minimising establishmentof pathogens by altering gut ecology and using antimicrobial agents; andeliminating pathogens from livestock manure. However, while there are manyinteresting strategies for reducing pathogen loads in animals there are far fewerexamples of strategies which are targeted, effective, affordable and widelyadopted. The greatest success has been seen in industrial poultry productionwhere biosecurity measures, pathogen-free birds, vaccination, and competitiveexclusion have been widely applied and have resulted in decreases in the loadsof potentially waterborne pathogens, especially Salmonella. The ability to highlycontrol the environment and exclude wildlife and alternative hosts undoubtedlycontributes to this success. In the case of ruminants, there are no widely used