Animal Waste, Water Quality and Human Health

166Animal Waste, Water Quality and Human HealthFigure 5.7 Mean prevalence of Giardia cysts in cattle faeces by region.The mean concentration of Giardia cysts in animal faeces is shown in Table 5.4.The highest mean concentration of Giardia cysts excreted per gram of animalfaeces was for muskrats (mean = 9574, n = 1), bison (mean = 2649, n = 1),beavers (mean = 1654, n = 1) and coyotes (mean = 1577, n = 1), respectively.The most numerous studies on Giardia cyst prevalence in animal faeces havebeen carried out on domestic livestock animals: cattle and pigs. The studies oncattle faeces were pooled for adult and juvenile animals to facilitate comparison ofgeographical regions (Figure 5.6). Unfortunately the majority of studies werecarried out in North America (n = 10) where Giardia prevalence was frequentlyin the range of 0% to 40%, with only one study reporting prevalence greaterthan 70%. Two studies were performed outside North America: one in Europerecorded a prevalence rate of 3.6% in adult cattle and one in Australasia recordeda prevalence rate of 89% in juvenile cattle. The paucity of data makes comparisonof regions difficult for prevalence rates of Giardia even in domestic livestockanimals.The lack of quantitative data on pathogen prevalence and concentrations inanimal faeces makes it difficult to gauge the relative risks of various animalspecies that can inhabit drinking-water catchments. Farm management practicescan reduce the impact of animal faecal source loadings if they are directed atfactors that control the level of microbial risk. The lack of quantitative data