Animal Waste, Water Quality and Human Health

Zoonotic waterborne pathogen loads in livestock 81shedding durations (Moore et al. 2003). The prevalence of presumptiveor DNA-confirmed Cryptosporidium parvum oocyst shedding is muchless common in older dairy calves, yearlings, and especially adult dairy cowswhere less than 10% of mature cattle shed this protozoal species (Atwill et al.1998, Sischo et al. 2000, Atwill & Pereira 2003, Santin et al. 2004, Starkeyet al. 2005, Kvac et al. 2006, Coklin et al. 2007, Guerden et al. 2007, Santinet al. 2008).Crypto. parvum oocysts / g faeces1.E+081.E+071.E+061.E+051.E+041.E+031.E+021.E+01WinterSummer1.E+000 5 10 15 20 25 30Day of ageFigure 3.1 Crypto. parvum oocyst shedding among dairy calves in central California, USA,adapted from Moore et al. 2003 and unpublished data, 2007.Beef calves and cows from cow-calf production systems, yearling beefreplacement heifers, and feedlot steers all appear to be less frequently infectedwith Cryptosporidium parvum than young dairy calves. For example, fewer than15% of preweaned range beef calves (two weeks to seven months) shed anyspecies of Cryptosporidium (Atwill et al. 1999). A faecal survey of seven beefcow-calf herds in western North Dakota found no calves or cows infectedwith Cryptosporidium parvum; instead, 9.4, 6.6 and 1.4% of animals sampledwere shedding Cryptosporidium bovis, Crypto. ryanae or Crypto. andersoni,respectively (Feltus et al. 2008). A survey of 22 feedlots in seven states(California, Washington, Colorado, Oklahoma, Texas, Nebraska, and SouthDakota) found no (0/5274) fresh faecal pats with detectable Cryptosporidiumparvum oocysts and 0.9% with Cryptosporidium bovis (Atwill et al. 2006). About