Animal Waste, Water Quality and Human Health

Zoonotic waterborne pathogens in livestock 117coli O157:H7, Campylobacter spp., Cryptosporidium parvum and Giardiaduodenalis (a.k.a. G. lamblia); other waterborne zoonoses (leptospirosis andschistosomiasis) are referred to as illustrative examples.The concept of key control points or multiple barriers applies from farm throughtransport to human exposure: because absolute control is not possible at everylevel, multiple barriers are required for safety so if one barrier should fail thenthe presence of others ensures water and food quality are maintained, and healthrisks minimized.Another insight from risk-based thinking is that processes are more manageablethan products. This concept is at the heart of Hazard Analysis and Critical ControlPoints (HACCP), the genesis of which was when scientists from the food industryhad to ensure safe meals for astronauts (Griffiths 1997). In setting up a HACCPsystem one attempts to identify all possible hazards and then identifies steps inthe process where action is necessary to prevent negative health outcomes(critical control points). In the context of this chapter, the desired “product” ispathogen-free animal wastes.Risks may have multiple sources and all sources must be synopticallyconsidered; for example, halving the cases of salmonellosis in cattle will havelittle impact on public health if 99% of cases originate from other humans orfrom non-bovine animals. But risk is also incremental, and in this context evensmall interventions may reduce risk sufficiently to make them worth their cost.Justifying interventions is further discussed in a subsequent Chapter, butespecially in low- and middle income countries the perfect is often the enemy ofthe good. High technology, high cost interventions remain all too often preferredover lower cost, more appropriate, somewhat less effective options that have farbetter prospects of sustainability.Case Study 1: Successful National Programmes to Control Salmonella in Poultry –When Interventions at Farm Level WorkSalmonellosis in humansSalmonella enterica serovar Typhi is a human-adapted pathogen associated with typoidfever and is a significant cause of waterborne disease in the developing world (Bhuniaet al. 2009). It is thought that cases of human illness associated with this serovar havedecreased in the developed world with the use of advanced systems to treat humansewage and chlorinate drinking-water (Leclerc et al. 2002). Non-typhoid Salmonellaserovars are typically associated with gastroenteritis in humans. However, illnesscaused by these Salmonella serovars can also result in septicaemia and death.Non-typhoid salmonellae are commonly derived from animal sources and are