Abstract |
A watershed in the western United States was surveyed biweekly for a year for the protozoa Cryptosporidium and Giardia. Parasite samples were collected using filtration of 200-1000 L of water, eluted by washing the filter, concentrated and clarified with density gradients. Oocyst and cysts were detected using monoclonal antibodies, in a direct or indirect immunofluorescent assay. From 39 samples, Cryptosporidium and Giardia were detected in 20 and 12 of the samples, respectively, and oocyst concentrations were approximately 10 times higher than cyst levels. Coliform levels ranged from 0.12 to 75 CFU/100 ml while fecal coliform levels were slightly lower. Giardia concentrations were significantly correlated to Cryptosporidium concentrations with an r value of 0.778, significant at the 99% confidence level. No other correlations were observed between Giardia and total or fecal coliforms or turbidities nor between Cryptosporidium levels and total or fecal coliforms or turbidities. Neither bacterial indicator organisms nor turbidity are reliable predictors for the absence of enteric protozoa in the study watershed. (Copyright (c) 1989 IAWPRC.) |