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  Animal Source Identification Using a Cryptosporidium DNA Characterization Technique (EPA/600/R-03/047) September 2002

This document summarizes the application of a particular molecular method to improve detection and differentiation of species and genotypes of Cryptosporidium oocysts found in environmental samples. Of particular interest is the method's potential for determining the source animals of oocysts in water samples. The molecular method is a nested polymerase chain reaction-restriction fragment-length polymorphism procedure that characterizes the small sub-unit ribosomal RNA gene. The method was previously developed for characterizing oocyst DNA from clinical samples.

The current project explores the method's applicability to environmental water samples, which have greater diversity of oocyst species and strains, lower concentrations of oocysts, and different interferents than clinical samples.

Results include:

  • Demonstrating that the method is capable of detection and differentiation of at least 10 species and 22 genotypes of Cryptosporidium
  • Demonstrating method sensitivity to a single oocyst with laboratory samples
  • Differentiating oocysts from oyster gill washings and hemolymph, and detecting them in storm water, surface water, and raw wastewater

The method's capability to determine an oocyst's source animal was demonstrated by identification in environmental water samples of host-adapted Cryptosporidium species and genotypes that were consistent with the source animal types (i.e., humans, farm animals, wildlife, and pets) inhabiting the sampled watersheds.


Michael Royer

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