Please find the link for the following US EPA method
Method 1623: Cryptosporidium and Giardia in Water by Filtration/IMS/FA10 - December 2005 Update (PDF, 76 pp., 1.2 MB)
Summary- This method (EPA 815-R-05-002) is a performance-based method applicable to the determination of Cryptosporidium and Giardia in aqueous matrices. Method 1623 requires filtration, immunomagnetic separation (IMS) of the oocysts and cysts from the material captured, and immunofluorescent assay (FA) for determination of the oocyst and cyst concentrations. A Training11 module is also available.