AWWA WQTC62399

AWWA WQTC62399 Identifying Host Adapted Cryptosporidium Species and Genotypes in Water
Conference Proceeding by American Water Works Association, 11/01/2005

Ruecker, Norma J.; Neumann, Norman F.

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It has become generally accepted that the genus Cryptosporidium is composed of anumber of host-adapted species and genotypes, with relatively few species or genotypescausing the majority of clinical disease in humans. Water is considered an importantvehicle of transmission for Cryptosporidium and a large emphasis has been placed on monitoring the occurrence and prevalence of Cryptosporidium in water. The US Environmental Protection Agency'sMethod 1623 is a commonly used and accepted method for quantifying the number ofCryptosporidium oocysts in water. However, in light of molecular advancements thathave led to a better understanding of the host-adapted nature of Cryptosporidium, basicquantification of oocyst concentrations in water provide inadequate information forassessing the environmental and public health risks associated with contamination ofwater sources with these parasites. A method of molecular forensic profiling has beendeveloped as an extension of Method 1623 to provide identification of the species andgenotypes of Cryptosporidium in water samples. Following quantification of oocysts bymicroscopy according to Method 1623, the slide material becomes the template formolecular analysis. The method consists of a replicated nested PCR-RFLP assay targetedagainst the 18S small ribosomal sub-unit RNA gene locus, with verification of RFLPpatterns by DNA sequence analysis. One of the strengths of the method is the ability toresolve single genotypes from mixed populations of Cryptosporidium spp. that may becommonly found in environmental water samples. Molecular forensic profiling by this method has provided important information regarding the host-sources impacting awatershed and the health risks associated with these contamination events; informationthat will be critical in designing new models of public health protection of drinking watersupplies based on comprehensive environmental risk assessments and source-to-tapwatershed management policies. Includes 48 references, tables, figures.