Animal Waste, Water Quality and Human Health

Exposure interventions 285domesticated animal populations. Increased human exposures may occur as aresult of increased leisure travel to regions where water-related diseases such asschistosomiasis, leptospirosis and others are endemic. The global nature of themarketplace also provides opportunities for the spread of disease: from wildpopulations to closely-associated domestic populations and ultimately a widergeographic spread through the transport of goods (Fouchier et al. 2005).Changes in human demographics at regional, national and global levels will beanother confounding factor, again possibly exacerbated by climate change andeffects resulting from displacement or changes to human migration patterns(Hess et al. 2008).In spite of limitations imposed by current faecal indicator assessments and thedifficulties in relating pathogen burden to human exposure risk in a definitive way,the need for intervention (management of the physical environment and of humanbehaviour) still exists. Adequate protection of public health necessitates themitigation or elimination of the pollution source or the prevention of exposurewhenever real human health risks exist. Early hazard detection and riskattribution are necessary and relevant to evidence-based interventions, rangingfrom herd management (both farmyard and field measures), to downstream bestmanagement practices, to regulation and policy development, and theimplementation of public education campaigns. The standardization of a stepwiseinvestigative framework may support the targeting of these interventionsand a logical progression may include the following:• Step 1 – develop an investigative framework for waterborne diseaseexposure interventions requiring the identification of credible microbialpathogens in the aqueous environment capable of causing disease inhumans (see: Chapter 2).• Step 2 – identification of a conveyance mechanism (water, sediments,intermediary hosts) capable of delivering the pathogen (see: Chapter 5,Haack et al. 2003); establishing an exposure route connecting the humanhost to the source (see: Chapter 7).• Step 3 – determine an attributable practice (i.e. agricultural, animalhusbandry, recreational, or cultural) which may be managed with theanticipated outcome being the reduction of the transmission risk and,ultimately of the disease burden.Management of pollutant sources or the affected populations does not comewithout cost and any intervention must weigh the expenditure against the directand indirect economic benefits (see: Chapter 12) and feasibility of a sustainedpositive outcome. The carbon cost of different mitigation options may also beconsidered, comparing, for example, the pouring of concrete and pumping