Animal Waste, Water Quality and Human Health

82Animal Waste, Water Quality and Human Health1% of the beef cows and 3% of their calves were positive for Cryptosporidium spp.in western Canada (Gow & Waldner 2006). About 0.5 to 1% of 367pre-weaned beef calves and none out of 2381 post-weaned beef calveshad detectable Cryptosporidium parvum oocysts in South Bohemia, CzechRepublic. Cryptosporidium parvum, along with Cryptosporidium bovis andCryptosporidium suis were detected in 12% of beef calves in Belgium;interestingly, the authors note that the production system for beef and dairy cattlein this part of Belgium are similar, functioning as a confined animal feedingoperation rather than an extensive grazing beef herd (Geurden et al. 2007).The geometric mean intensity for all three species of Cryptosporidium was780 oocysts/g faeces. Cryptosporidium parvum was detected in less than 10% ofbeef calves in Zambia (Geurden et al. 2006).Cryptosporidium parvum in sheep and goat herds tends to occur morefrequently in pre-weaned animals than in older animals (Robertson, 2009), butthe reported prevalence rates of faecal shedding can vary widely from region toregion. For example, 13% (63/477) of pre-weaned lambs had detectableoocysts compared to none (0/500) of post-weaned sheep in Australia, withinfected lambs apparently shedding low oocyst numbers (Ryan et al. 2005,Yang et al. 2009). The prevalence of Cryptosporidium spp. was 13.1% inlambs and 9.5% in goat kids in Belgium, with almost none of the isolates insheep yet all of the isolates in goats confirmed as Cryptosporidium parvum(Geurden et al. 2008). The mean intensity of oocyst shedding for all species ofCryptosporidium was ∼6800 and ∼232,000 oocysts per gram faeces for sheepand goats, respectively (not adjusted for % recovery) (Geurden et al. 2008).Assuming adult sheep produce 0.7 kg faeces per day, this would generate amean daily environmental loading rate of 4 × 10 6 oocysts per sheep per day. Incontrast, Cryptosporidium parvum was the only species identified amongdiarrheic lambs in Spain (Quilez et al. 2008). Sampling of lambs and adultsheep in the UK during human cryptosporidial follow-up investigations found36% (94/261) of animals shedding Cryptosporidium spp., but only 9.2% wereconfirmed as Cryptosporidium parvum (Mueller-Doblies et al. 2008).Ortega-Mora (1999) measured a range of oocyst shedding intensities between20 and 440 Cryptosporidium spp. oocysts/g faeces among adult sheep in Spain(Crypto. parvum not DNA-confirmed), with the average number of oocysts/gfaeces being ∼50 and ∼90 on two different farms. Assuming adult sheepproduce 0.7 kg faeces per day, this would generate a mean daily environmentalloading rate between 35,000 and 63,000 oocysts. Lambs experimentallyinoculated with a cervine-ovine isolate of Cryptosporidium spp. excreted anarithmetic mean of 4 × 10 9 oocysts/g faeces, of which half were determined tobe non-viable and therefore reducing the estimated intensity by 50% (Bukhari &