Animal Waste, Water Quality and Human Health

Zoonotic waterborne pathogen loads in livestock 97young stock, yearlings, and adults together). Such data will help match the seasonalenvironmental loading rate to seasonal intervention strategies and better alert waterquality managers when highly infected populations are present on the watershed.100%Probability to detect 1 or more oocysts75%50%25%IMS-DFADT 50 = 1.0DT 90 = 3.2DFADT 50 = 200DT 90 = 6300%1 10 100 1,000 10,000No. of oocysts / g faecesFigure 3.3 The probability of detecting Crypto. parvum oocysts in bovine faeces for two assays:immunomagnetic separation followed by immunofluorescent microscopy (IMS-DFA) andimmunofluorescent microscopy alone (DFA). DT 50 and DT 90 are the oocyst concentrationsdetected with 50% and 90% probability, adapted from Pereira et al. 1999 and Atwill et al. 2003.Certain age classes of animals tend to be more susceptible to infection thanothers and may even be infected by different subtypes of organisms than adults.It is known that manure from calves is likely to contain higher levels ofzoonotic pathogens such as Cryptosporidum parvum and E. coli O157:H7 thanmanure from adults, and that on both a relative (concentration of organisms perunit of weight) and absolute basis (number of organisms excreted per animal)represent a greater risk as a source of these waterborne zoonotic pathogens thanmanure from adults. This “high risk” manure may need to be processed morethoroughly than wastes from adults to decrease pathogen numbers in theenvironment and the associated human health risks.Certain human hosts, particularly those who are immunologically naïve orimmuno-compromised (e.g. individuals with HIV infections, patients undergoingchemotherapy, and the elderly) are more susceptible to illness caused bywaterborne pathogens. However, differences in the genetic susceptibility ofindividuals in the population also likely play a role in susceptibility to theseinfections. As in human hosts, there are also likely to be differences