Animal Waste, Water Quality and Human Health

Comparative risk analysis 365waterborne outbreaks or with faecal contamination of water. The following criteriahave been adopted whereby pathogens from the list above will be selected forinclusion in our risk comparison process.• The pathogens are known to be carried by animal or bird species;• The pathogens are discharged in the faeces of animals or birds;• The pathogens have been isolated from surface waters;• The pathogens cause disease in humans.The zoonotic pathogens that meet these criteria are:E. coli O157 (more generally, EHEC) which are predominantly carried byruminants including beef and dairy cattle and sheep (USEPA 2000a, Caprioliet al. 2005) and, to a lesser extent, monogastric animals (Chapman 2000,Chapman et al. 1997). This organism has been associated with outbreaks ofdisease that are related to recreational water (e.g. Keene et al. 1994) and hasbeen isolated from surface waters. None of the outbreaks have been linkeddirectly to direct contacts with animals. However, some have been associatedwith food and drinking-water.Campylobacter species are frequently found in surface waters and this organism iscarried by poultry, cattle and sheep (Jones 2001). Campylobacter has frequentlybeen linked to outbreaks transmitted by food and water, but its occurrence ispredominated by sporadic and endemic patterns, rather than outbreaks. InNew Zealand, where campylobacteriosis is a reportable disease, about 300 to400 cases per hundred thousand population have been reported in recent years(Till & McBride 2004, Till et al. 2008). 2 In western and northern Europe, inthe late 1990s reported rates per 100,000 varied from ∼20 (The Netherlands)to ∼100 (England Wales) (Kist, 2002). Annual reported incidence in Australiais ∼100/100,000 (NNDSS, 2010) and in Canada seems to be declining but atthe time of writing is ∼30/100,000 (PHAC, 2010). It is important to note thatthe actual incidence of this disease in the USA is estimated to be ∼40 timeshigher than the reported rate (Mead et al., 1999), because many cases are notdetected by a country’s health reporting system. 323This rate has approximately halved in recent years. This has been attributed to managementinterventions in the poultry industry (French et al. 2011, McBride et al. 2011).The many reasons for this state of affairs are often described by the “reporting pyramid” (e.g., Lakeet al. 2010). Layers in this pyramid depict all the necessary steps that must be taken before it ispossible to report incidence. For example, an ill person must visit a doctor who must request thata stool sample be supplied and analysed for the presence of Campylobacter, an infected stoolmust be supplied and analysed correctly, and a positive result must be entered into the reportingsystem. If any one of these steps is not completed, the case will not be reported.