Technical note: A guide for optimizing sample volume for the detection of Cryptosporidium oocysts by USEPA method 1622

Cryptosporidium analyses usually result in a high incidence of nondetectable samples because of low concentrations of oocysts and low recovery efficiencies in environmental water, suggesting greater volumes of water samples. However, there are limitations in analyzing high sample volumes, such as low filter performance and limited volume-processing capabilities when using US Environmental Protection Agency method 1622. This study provides guidelines for using water turbidity measurements to determine optimum sample volumes for the detection of Cryptosporidium oocysts using method 1622. The purpose of collecting larger volumes of water samples is not necessarily to increase the effective sample volume. The optimum sample volumes suggested in this article can minimize the method's limitations and consequently achieve better recovery of oocysts in water. Use of the optimum-volumes strategy suggested in this study would save sample filtration time, enhance filter performance, and offset the poor recovery efficiency of oocysts that typically results from higher volumes of water and high turbidity.