The occurrence of Cryptosporidium in environmental waters in the greater Dublin area

Grab samples of 101 of raw water were taken on a weekly basis from five sam pling sites in the greater Dublin area. Water from four of the five samplin g sites was ultimately intended for human consumption. The samples were pro cessed by calcium carbonate flocculation followed by sucrose flotation and labelling with a monoclonal antibody, and the number of Cryptosporidium ooc ysts present in each sample was determined by fluorescence microscopy. Oocy sts were found at each sampling site on at least one occasion during the sa mpling period. The maximum number of oocysts found at any particular site w as 6 oocysts/l. The maximum number of oocysts at three of the sites was fou nd after a period of heavy rainfall that was thought to have increased leve ls of runoff into the water bodies. The results of the sampling indicated t hat Cryptosporidium oocysts are widely disseminated in the aquatic environm ent of the greater Dublin area. (C) 2000 Elsevier Science Ltd. All rights r eserved.