ISO 15553:2006 specifies a method that is applicable for the detection and enumeration of Cryptosporidium oocysts and Giardia cysts in water. It is applicable for the examination of surface and ground waters, treated waters, mineral waters, swimming pool and recreational waters.

This method does not allow identification to species level, the host species of origin or the determination of viability or infectivity of any Cryptosporidium oocyst or Giardia cyst which may be present. These procedures are for use by experienced analysts who have successfully completed competency tests prior to commencing analysis.