Theoretical implications of best management practices for reducing the risk of drinking water contamination with Cryptosporidium from grazing cattle

Abstract A synthesis of the literature on the incidence of Cryptosporidium parvum in cattle, the fate of both feces and C. parvum in the environment, and the implications for BMP to alter both the incidence of exposure of surface water sources to C. parvum contaminated feces and its fate was conducted. The results reveal that cattle are a possible source of C. parvum contamination to surface water sources in mixed-use watersheds. In a worst case scenario, surface water sources could be exposed to a load of up to 300 × 10 10 C. parvum oocysts per day in a herd of 300 cow-calf pairs. This would theoretically pose a threat to human health. Six proposed best management practices (BMPs) were examined to determine if they could theoretically reduce the magnitude of the risk that cattle grazing in multiuse water sheds might pose. The BMP of scheduling the access of cattle such that no calves younger than three months of age are permitted near sensitive riparian areas in community watersheds, provided global risk minimization regardless of the site specific BMPs used. Other BMPs including off-stream watering, stubble height management in key areas and silvopasture with off stream watering reduce the risk of C. parvum entering surface waters in amounts high enough to cause a risk to drinking water consumers. The BMP of fencing and nose holes to restrict access may be problematic as these create corridors and damage the riparian habitat if they are placed incorrectly. Overall, any risks that are inherent to allowing cattle to graze on the land in multiuse watersheds can be minimized with the use of several best management practices.