Animal Waste, Water Quality and Human Health

Zoonotic waterborne pathogen loads in livestock 79pathogenic microbial species would be E. coli O157:H7 in North America, wheremore than 90% of sporadic and outbreak cases of haemorrhagic colitis and thehaemolytic uremic syndrome (HUS) are associated this serotype (Gyles 2007,Karmali 2005, Karmali et al. 2009), specific multi-locus sequence typing(MLST) patterns for Campy. jejuni in the UK (Sheppard et al. 2009),assemblages A and B for Giardia duodenalis (Hunter & Thompson 2005), andthe Crypto. parvum GP60 IIa subtype (Feltus et al. 2006).The discovery of the host-specificity of certain pathogen subtypes has given riseto the suggestion that their genetic fingerprints may be useful in determining thesources of water contamination with animal wastes. However, to be successfullyused in tracking host sources of faecal contamination, the agents have to bewidespread in the host population, be shed in very large numbers, be relativelystable and be detectable using simple laboratory tests.3.2 WATERBORNE ZOONOTIC PROTOZOATwo protozoa, Cryptosporidium parvum and Giardia duodenalis, are classified ashigh priority waterborne zoonoses. Crypto. parvum and G. duodenalis are able toinfect humans at very low doses (Okhuysen et al. 1999, Chappell et al. 2006), theycan survive in cool water for extended periods of time (especially Crypto. parvum)and can resist many chemical disinfectants (especially Crypto. parvum; Korichet al. 1990, Erickson & Ortega 2006), and are unable to replicate in theenvironment. Once the faecal load of these protozoa has been deposited in theenvironment by animals, the (oo)cyst numbers begin to decline in both faecesand water due to a variety of natural processes, especially once temperaturesexceed 40°C (Li et al. 2005, Gomez-Couso et al. 2009). The epidemiology andmanagement of protozoal zoonoses hence differs in some respects from thebacterial waterborne zoonoses (E. coli O157:H7, Salmonella enterica, andCampylobacter). Crypto. parvum and G. duodenalis are found throughout theworld, can coexist in the same host and are commonly transmitted usingfaecal-oral and waterborne transmission pathways. Although Cryptosporidiumhominis is a common cause of human cryptosporidial infection in many locationsaround the world, this species is shed mostly by humans and only occasionally byother animals (Hunter & Thompson 2005).3.2.1 Cryptosporidium parvumCrypto. parvum is a protozoan or single-celled parasite that infects humans anda variety other mammalian species, including different species of livestock