Although there are many methods in the literature for detection or enumeration of Crytosporidium oocysts and Giardia cysts in water samples, the USEPA-validated method and the preferred method for monitoring is Method 1623—filtration/immunomagnetic separation (IMS)/fluorescent antibody (FA). Method 1622 was developed and tested earlier by USEPA and is for detection of Cryptosporidium oocysts only. Method 1623 is described on this page because it is the most current method.

Because of the complexity of Method 1623, it must be performed by an experienced analyst.  (See USEPA, 2001.) The laboratory must also have satisfactory Ongoing Precision and Recovery (OPR) data.  Because recoveries may be highly variable, it is recommended that a matrix spike, containing a known amount of oocysts and cysts, be analyzed for each water matrix.

THEORY: A 10-L water sample is collected and shipped to the laboratory.  The sample is filtered in the laboratory, and cysts and oocysts are eluted from the filter. The eluate is concentrated by centrifugation.  The oocysts and cysts in the pellet are then mixed with magnetic beads conjugated to anti-Cryptosporidium and anti-Giardia antibodies.  The magnetized oocysts and cysts are separated from particulates using a magnet.  After the cysts and oocysts are separated from the magnetic beads, they are stained on well slides with fluorescently labeled monoclonal antibodies and 4’,6-diamidino-2-phenylindole (DAPI).  Each well slide is scanned for objects that meet the size, shape, and fluorescence criteria for Crytosporidium and Giardia.

USE: Method 1623 was developed and tested by USEPA to assess Crytosporidium and Giardia occurrence in raw surface waters and other waters.  This method will not identify the species of Cryptosporidium or Giardia or the host species of origin, nor can it determine the viability or infectivity of detected oocysts and cysts.

REFERENCES: 

U.S. Environmental Protection Agency, 1998, Method 1622—Cryptosporidium in water by filtration/IMS/FA: Washington , D.C. , EPA-821-R-98-010, 44 p.

U.S. Environmental Protection Agency, 2001, Method 1623: Cryptosporidium and Giardia in water by filtration/IMS/FA: Washington , D.C. , EPA-821-R-01-025, 52 p.

NWIS PARAMETER CODES:

99599  Cryptosporidium, water, Method 1623, oocysts per 10 L

99600  Cryptosporidium, spike efficiency parameter code 99599, percent recovery

99597  Giardia, water, Method 1623, cysts per 10 L

99598  Giardia, spike efficiency parameter code 99597, percent recovery

Report as presence oocysts per 10 liters for Cryptosporidium or cysts per 10 liters for Giardia.

U.S. Department of the Interior, U.S. Geological Survey
Email Maintainer: webmaster  for comments, suggestions, etc.
Privacy Statement || Disclaimer || Accessibility

Last update: October 2003