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Applied and Environmental Microbiology, March 2006, p. 1810-1816, Vol. 72, No. 3
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.3.1810-1816.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Deposition of Cryptosporidium Oocysts in Streambeds

Kristin E. Searcy,^1* Aaron I. Packman,¹ Edward R. Atwill,² and Thomas Harter³

Department of Civil and Environmental Engineering, Northwestern University, Evanston, Illinois 60208,¹ Veterinary Medicine Teaching and Research Center, School of Veterinary Medicine, University of California—Davis, Tulare, California 93274,² Department of Land, Air, and Water Resources, University of California—Davis, Davis, California 95616³

Received 17 June 2005/ Accepted 15 December 2005

The transfer of Cryptosporidium oocysts from the surface water to the sediment beds of streams and rivers influences their migration in surface waters. We used controlled laboratory flume experiments to investigate the deposition of suspended Cryptosporidium parvum oocysts in streambeds. The experimental results demonstrate that hydrodynamic interactions between an overlying flow and a sediment bed cause oocysts to accumulate in the sediments and reduce their concentrations in the surface water. The association of C. parvum with other suspended sediments increased both the oocysts' effective settling velocity and the rate at which oocysts were transferred to the sediment bed. A model for the stream-subsurface exchange of colloidal particles, including physical transport and physicochemical interactions with sediment grains, accurately represented the deposition of both free C. parvum oocysts and oocysts that were attached to suspended sediments. We believe that these pathogen-sediment interactions play an important role in regulating the concentrations of Cryptosporidium in streams and rivers and should be taken into consideration when predicting the fate of pathogens in the environment.

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* Corresponding author. Mailing address: Department of Civil and Environmental Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208. Phone: (847) 467-4980. Fax: (847) 491-4011. E-mail: k-searcy{at}northwestern.edu.

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Applied and Environmental Microbiology, March 2006, p. 1810-1816, Vol. 72, No. 3
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.3.1810-1816.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

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