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EVALUATION OF CRYPTOSPORIDIUM OOCYSTS AND GIARDIA CYSTS IN A WATERSHED RESERVOIR
Citation:
AZADPOUR-KEELEY, ANN, B. R. FAULKNER, AND M. CALDWELL. EVALUATION OF CRYPTOSPORIDIUM OOCYSTS AND GIARDIA CYSTS IN A WATERSHED RESERVOIR. Presented at 105th General Meeting of American Society for Microbiology, Atlanta, GA, June 05 - 09, 2005.
Impact/Purpose:
To inform the public.
Description:
This investigation evaluated the occurrence of Cryptosporidium oocysts and Giardia cysts at 17 sampling locations in Lake Texoma reservoir using method 1623 with standard Envirocheck" capsule filters. The watershed serves rural agricultural communities active in cattle ranching, recreation, and is a potential drinking water source. A total of a 193 surface water samples were tested over a 27 month period to determine levels of parasite contamination. The overall occurrence of the Cryptosporidium oocysts were higher in both magnitude and concentrations than Giardia cysts. Cryptosporidium oocysts were found in 99% (192 of 193) and Giardia cysts were detected in 87% (169 of 193) of the samples. Although Cryptosporidium and Giardia occurrence were significantly, but not strongly correlated (Pearson correlation coefficient 0.488, p <0.0001), all other correlation coefficient including turbidity [NTU] and total dissolved solids (TDS) were non-significant. Statistically supportable seasonal variations were found suggesting that Cryptosporidium and Giardia were higher in summer and fall than in other seasons of the year. The maximum numbers for both protozoan parasites were detected from a site impacted by cattle ranching in October 2000 and March 2002 which coincided with calving activity. Confirmation of species for select positive protozoan samples was made by using a nested PCR restriction fragment polymorphism assay. The detection of oocysts and cysts in Lake Texoma demonstrates important public health concerns with the protozoa. One plausible management practice includes livestock control by restricting their access to creeks which are tributaries to the reservoir and by fencing to prevent widespread surface water contact.