Animal Waste, Water Quality and Human Health

116Animal Waste, Water Quality and Human Healthdeleterious impacts on both human and animal populations, the objectives are toboth improve food safety and reduce production losses. A subsequent Chapterdiscusses some of the implications when effective control requires coordinationof multiple actors and where costs are borne by one actor but benefits accrue tomultiple actors, which may or may not include the actor investing in control.4.2 RISK-BASED APPROACHES AND THE RATIONALEFOR ANIMAL-BASED INTERVENTIONSRisk-based approaches provide a rationale for tackling waterborne zoonoses at thefarm level. A cornerstone of risk analysis is the concept of a “risk pathway” thattraces hazards from their source to the associated health outcome: pathscommonly referred to as gate to plate, farm to fork, boat to throat and, whenapplied to water treatment, source to tap (Hamilton et al. 2006). This impliesthat controlling hazards at source will have benefits all the way down therisk pathway, and, indeed, it has been suggested that the farm is often the bestplace to control food and waterborne pathogens (Hafez 1999). Figure 4.1 setsout points at which pathogens can be controlled as they move fromenvironment/other animals to infect farm animals, then establish infection in thegastrointestinal system (GIT) of livestock, and eventually are shed in excreta.These are considered in detail in the rest of the Chapter as four key controlpoints to ensure animal excreta are free from waterborne zoonoses.2. Block establishment:↑ host resistance1. Minimiseexposure3. Block establishment:GIT ecology/antimicrobials4. Eliminate from faecesFigure 4.1 Points at which pathogen load can be reduced in farm animals and their excreta.In keeping with the rest of the book, this chapter focuses on the five prioritywaterborne zoonoses identified in Chapter 2: Salmonella enterica, Escherichia