Please find the link for the following US EPA method

Method 1622: Cryptosporidium in Water by Filtration/IMS/FA12 - December 2005 Update (PDF, 75 pp., 1.3 MB)

Summary - This method (EPA 815-R-05-001) is a performance-based method applicable to the determination of Cryptosporidium in aqueous matrices. Method 1622 requires filtration, immunomagnetic separation (IMS) of the oocysts from the material captured, and immunofluorescent assay (FA) for determination of the oocyst concentration. There are also forms associated with Method 1622. A Training11 module is also available.

http://www.epa.gov/nerlcwww/1622de05.pdf