Animal Waste, Water Quality and Human Health

Assessing the importance of zoonotic waterborne pathogens 43adults. Interestingly, host-restriction appears to be accompanied by a reductionin genome size for both Salm. typhi and serovar Typhimurium (Kingsleyet al. 2009).In the developed world, most autochtonous outbreaks of salmonellosis arefoodborne and of animal origin (Majowicz et al. 2010). In contrast to the highlyhost-specific serovars associated with human enteric fevers, many NTS serovarsappear to have a broad host range and are frequently associated with humaninfections. Other NTS serovars, however, appear to be relatively host-restrictedand are rarely the cause of human disease (e.g. NTS serovar Gallinarum inpoultry). In developed countries, significant efforts have been made to reducerisks associated with the organism throughout the entire food chain, from farmgate to the consumer’s plate. As mentioned above, waterborne transmission ofSalmonella has been decreased significantly (but certainly not prevented) bychlorination and other modern source water and waste water treatment procedures.In the United States, among the 479 foodborne disease outbreaks of knownetiology reported in 2008, Salmonella accounted for 23% of outbreaks and 31%of illnesses (MMWR, 2011). According to the European Food Safety Authoritythere were over 100,000 human cases of salmonellosis reported in 2009 amongthe member states; the economic loss associated with this burden of disease wasestimated at 3 billion Euros (EFSA, 2011). These figures only reflect cases andoutbreaks which were identified by health authorities, however. The true burdenof disease is thought to be much higher. Scallan et al. (2011) have recentlyestimated that there may be as many as 1.2 million episodes of illness associatedwith NTS each year in the United States resulting in more than 23,000hospitalizations and 450 deaths and a recent global estimate suggests an annualrate of NTS-related illness of 93.8 million episodes with 155,000 deaths – 80.3million episodes being foodborne (Majowicz et al. 2010).In the EU control efforts have focused on Salmonella Enteriditis andTyphimurium which together account for 75% of human cases. SalmonellaEnteriditis is acquired from poultry and eggs, while Salmonella Typhimuriuminfections largely come from eating contaminated pork, beef and poultry. InUnited States, Salmonella serovars associated with human disease appear to besomewhat more diverse with Salmonella Enteriditis, Typhimurium, Newportand Heidelberg serovars representing 45% of the isolates from humans andtogether with 16 other serovars make up 70% of the human Salmonella isolates.Hara-Kudo & Takatori (2011) recently reported the infectious dose for NTS tohave been as low as 89 CFU in one outbreak with exposures as high as 14 × 10 9CFU in another. Predictably, higher exposures were associated with higher ratesof infection (up to 100%). However, differences in virulence among serovars arealso likely to influence the infectious dose and infection rates.