Animal Waste, Water Quality and Human Health

Zoonotic waterborne pathogen loads in livestock 933.3.3.1 Salmonella serotypes associated with human infectionOver 90% of human, avian, and other mammalian infections are attributed toserotypes from Salm. enterica subspecies enterica, with the majority of humaninfections in the European Union and the USA caused by a small number ofserotypes within this subspecies, such as Salm. enterica subsp. enterica serotypesTyphimurium and Enteritidis (Olsen et al. 2001). It is estimated that in the USA1.4 million human infections and 400 to 600 deaths occur each year from thesevarious Salm. enterica subsp. enterica serotypes (Mead et al. 1999, Voetschet al. 2004), with 95% of these infections due to a foodborne transmission (Meadet al. 1999). These infections can be fatal in the immunocompromised, in youngchildren, and in the elderly. Most clinical illness appears to be sporadic, althoughoutbreaks do occur. Foods often implicated in outbreaks include poultry andpoultry products, meat and meat products, dairy products, egg products, seafood,and fresh produce. Salm. enterica subsp. enterica serotype Enteritidis is nowone of the most common serotypes isolated from human disease cases and isassociated with the eating of undercooked eggs (Mishu et al. 1994, Patrick et al.2004). Interestingly, relative to the protozoan parasites, Crypto. parvum and G.duodenalis, and E. coli O157:H7, few outbreaks of Salm. enterica have beenassociated with exposure to recreational water or to drinking-water, despite itswidespread occurrence in domestic and wild animals. Many of the serotypes ofSalm. enterica shed by domestic animals and wildlife are infrequent causes ofhuman illness, such as Salm. enterica serovar Dublin (CDC, 2005). Either illnessassociated with these rare serovars of Salm. enterica is seldom diagnosed, humanexposure to these serovars is infrequent, or the infectious dose for humans is veryhigh. It is also likely that there are host-adapted serovars of the organism that arerarely associated with disease because of inter-species barriers in transmissionand survival. However, there are other Salm. enterica serovars which arewidespread and are commonly isolated from multiple host species and arefrequently associated with human infections, such as Salm. enterica serovarTyphimurium.3.3.3.2 Shedding of Salmonella by livestockAnimals used for food production are common carriers of numerous serovars ofSalm. enterica, with a wide range of prevalence in different livestock species. Asurvey of layer facilities in the USA found that 7.1% were positive forSalmonella Enteritidis (Garber 2003), with this bacterium frequently present inthe litter (Davies & Breslin 2003). It is estimated that about 30% of dairy herdsacross the USA have cattle shedding Salmonella (NAHMS, 1996; NAHMS,