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Cryptosporidium Source Tracking in the Potomac River Watershed
Citation:
Wang, W., P. Chen, E. VILLEGAS, R. B. LANDY, C. KANETSKY, V. Cama, T. Dearen, C. Schultz, K. G. Orndorff, G. J. Prelewwicz, M. H. Brown, AND K. R. Young. Cryptosporidium Source Tracking in the Potomac River Watershed. Presented at 10th International Workshop on Opportunistic Protists, Boston, MA, May 28 - 31, 2008.
Impact/Purpose:
The overall objective of this task is the development of improved occurrence detection methods for protozoan parasites and Microsporidia. Since this work is a primary focus of the Branch, this task supports several individual projects related to sample preparation and protozoan detection. Together these projects will lead to complete methods able to support the UCMR and the CCL2 and CCL3.
Description:
To better characterize the presence of Cryptosporidium in the Potomac River watershed, a PCR-based genotyping tool was used to analyze 64 base-flow and 28 storm-flow samples from five sites within the watershed. These sites included two water treatment plant intakes as well as three upstream sites, each associated with a different type of land use. Each of these uses, urban/wastewater, agricultural (cattle)/wastewater, and agricultural (cattle), posed different risks with regard to the potential contribution of Cryptosporidium oocysts to the source water. In the study, Cryptosporidium was detected in 27 base-flow water samples and 23 storm-flow water samples. The most frequent genotype detected was C. andersoni (detected in 41 samples), while 14 other species/genotypes, almost all wildlife-associated, were occasionally detected. The two common human-pathogenic species, C. hominis and C. parvum, were not detected. Although C. andersoni was common at all four sites under agricultural influence, it was largely absent at the urban/wastewater site. There were very few positive samples by EPA Method 1623 at any site; only eight of 90 samples (9%) analyzed were positive for Cryptosporidium by microscopy. The genotyping results suggest that much of the Cryptosporidium that is present in the water treatment plant source waters may not pose a significant human health risk.