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C:ryptospondium (part 1 of 2) Page 8 of 13 <br /> �� g�l� <br /> ■ The species of Cryptosporidium cannot be distinguished using conventional <br /> methods. <br /> ■ Some of the antibodies used for detection may cross-react with other organisms <br /> (e.g., yeasts) so that enumeration of oocysts may include species (or other <br /> organisms) that are not infectious to humans <br /> ■ Detection of the oocysts does not indicate whether they are viable (i.e., capable of <br /> inducing infection). <br /> ■ There is no method for assessing the virulence (i.e., the severity of the disease <br /> produced) of a particular strain of Cryptosporidium. <br /> ■ Current concentration techniques result in recoveries in the range of only 20 to 70 <br /> percent with the efficiency being a function of the water matrix. <br /> ■ Variations between laboratories for identical samples can be as high as 100 <br /> percent, even through improvements to standardized procedures used for the <br /> EPA's Information Collection Rule sampling, these wide variations have somewhat <br /> reduced. <br /> Development work has been conducted on better concentration techniques (e.g., <br /> immunomagnetic separation), specific identi�cations with DNA probe technology (i.e., <br /> using polymerase chain reaction) , and assessment of viability (i.e., through ELISA/RT- <br /> PCR or PI/DAPI staining). <br /> Due to the significant uncertainties in the methods, the numerical values produced are <br /> only rough estimates. This creates challenges for communicating data to the general <br /> public. <br /> There is some indication that particle counting may be a useful surrogate for assessing <br /> efficiency of Cryptosporidium removal by water treatment processes. <br /> North American Source Waters <br /> Typical geometric average concentrations for various water types have been as <br /> follows: <br /> ■ Lakes - 0.44 oocysts per liter <br /> ■ Rivers - 0.43 oocysts per liter <br /> ■ Springs - 0.04 oocysts per liter <br /> ■ Groundwater - 0.003 oocysts per liter <br /> In North American waters, the values of Cryptosporidium range from 0.002 to 5,800 <br /> oocysts per liter, depending on the source. These values will vary depending on the <br /> watershed characteristics of the water source. Concentrations of Cryptosporidium <br /> oocysts in source water tend to be higher than Giardia. <br /> North American Treated Waters <br /> http://sfwater.org/printContent.cfin/C_ID/446/ 10/19/2004 <br /> i � __ , <br />