Improvements in Cryptosporidium recovery and variability through modifications to United States Environmental Protection Agency Method 1623

The use of United States Environmental Protection Agency (USEPA) Method 1623 for the detection of Cryptosporidium in water often results in low and variable rates of recovery. According to data disseminated in Method 1623, less than a quarter of tested surface water samples had Cryptosporidium recoveries of 60% or greater. This research explored various method modifications in order to produce a method with higher recovery and less variability. Once method modifications were implemented, recoveries of C.parvum in reagent water increased by greater than 20% to an average recovery of 76%. In surface water, a significantly higher (P=0.049) mean recovery of 67% for C.parvum was achieved with the modified method. Giardia is simultaneously detected when using Method 1623. The method modifications significantly increased the recovery of Giardia in reagent water by 37% (P=0.0002) while also allowing for a 17% higher recovery in surface water samples (P=0.21).