Current UK methods for the isolation and enumeration of Cryptosporidium spp oocysts and Giardia spp cysts in water concentrates are time-consuming and inefficient, providing minimal information regarding the biology of the organism. Minimising the portion of sample concentrate examined can reduce the level of confidence in the result obtained and this issue requires appreciation by the water regulators. Alternative methods for isolation and enumeration require corroboration with the established method using a variety of water types. Developments that increase information regarding the biology of these organisms should be encouraged. Not only does method performance (recovery efficiency, reproducibility etc), but also method significance (integrity of health, operational and regulatory assessments etc) require to be addressed. For Cryptosporidium the fluorogenic viability assay can not only assist in the decisions taken by health officials when oocysts are found in water supplies but also in designing catchment assessment and sampling policies for individual treatment plants, yet few laboratories are experienced in this assay.

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