Animal Waste, Water Quality and Human Health

118Animal Waste, Water Quality and Human Healthprimarily transmitted to humans through contaminated foods but are also occasionallyassociated with waterborne disease (Callaway et al. 2007, Franklin et al. 2008,Schuster et al. 2005). While there are over 2500 serovars of Salmonella, only ahandful of these are commonly associated with human disease. For example, in Europemore than 70% of human infections are associated with Salmonella serovars Enteriditisand Typhimurium (EFSA 2006).Salmonella in poultrySalmonella serovars Gallinarium and Pullorum were a common cause of productionlosses to the poultry industry in the first half of the 20 th century (Cogan & Humphrey2003). However, disease associated with these two serovars in poultry wassuccessfully controlled through vaccination and led to their virtual eradication by themid 1970s. It has been postulated that the decrease in these serovars in poultryprovided a vacant niche which allowed Salmonella serovar Enteriditis to establish afoothold. In contrast to serovars Gallinarium and Pullorum, Enteriditis is notassociated with disease in poultry but is very commonly associated with humandisease. By 1997, foodborne illness associated with Salmonella serovar Enteriditishad risen from 10,000 to over 30,000 cases per year in the United Kingdom andaccounted for about 70% of human Salmonella infections. It was shown thatsalmonellosis was associated with the consumption of poultry and that phage type 4of Salmonella serovar Enteriditis-related disease was specifically associated with theconsumption of shelled eggs. Similar Enteriditis-associated epidemics were alsoobserved in other European countries and the USA at this time (Braden 2006, Patricket al. 2004, Poirier et al. 2008, Wegener et al. 2003).On farm control of Salmonella in poultrySalmonella control programmes adopted in the European Union and in other developedcountries around the world have certain elements in common but also maycontain country-specific elements. Perhaps the most important of these is to have aSalmonella control plan with specific reduction targets. Many programmes emphasizethe importance of strict biosecurity measures including the provision of physicalbarriers, limited access, “all in, all out” management systems and clean feed andwater, in attempts to prevent horizontal transmission of these pathogens. While thesemeasures may be suitable for keeping Salmonella out of clean flocks, they cannot beused to eliminate established infections. In order to do this one must start with cleanseed stock. In both the broiler meat and table-egg industries significant efforts havebeen made towards a top-down approach to eliminate Salmonella from elite,grandparent and parent breeder flocks. Bacteriological and serological testing ofsamples is undertaken at multiple points in the production cycle of breeder flocks todetermine their infection status. Salmonella-positive flocks are depopulated and barns