Qualitative Risk Assessment of Surface Water Contamination with Cryptosporidium Sp. Oocysts: A Case Study of Three Agricultural Catchments

In recent years there have been a number of waterborne outbreaks of cryptosporidiosis in some major urban centers in Ireland. The Irish Environmental Protection Agency has adapted and modified the qualitative “Scottish Water Directions” to help prevent such outbreaks. When this risk assessment method was applied to three small agricultural river catchments in Ireland, the results suggested an equal risk of water contamination for each catchment. A survey was conducted in each catchment focusing on agricultural activity and surface waters. Fecal samples were collected from 1–8-week-old calves along with associated slurry and dung from beef and dairy farms and water samples were collected monthly at the outlet of the three catchments. Two of the catchments had much higher infection rates among neonatal calves as well as higher oocyst contamination of surface waters than the remaining one. It was concluded that the qualitative risk assessment could be more robust if cognizance was taken of the temporal and epidemiological aspects of cryptosporidiosis in beef and dairy herds.