A RAPID VIABILITY ASSAY FOR CRYPTOSPORIDIUM OOCYSTS AND GIARDIA CYSTSFOR USE IN CONJUNCTION WITH INDIRECT FLUORESCENT-ANTIBODY DETECTION

There is an ur ent need to develop rapid methods to determine the viab ility of Cryptosporidium oocysts and Giardia cysts in environmental sa mples, especially water. The inclusion of the vital dye propidium iodi de (PI) by oocysts and cysts has been previously shown to correlate we ll with nonviability. The ability of nonviable oocysts and cysts to in clude PI has been employed to develop a rapid viability determination method that could be used in conjunction with the current indirect flu orescent antibody (IFA) method for detecting oocysts and cysts, The ef ficacy of this PI-IFA method to detect and determine the viability sta tus of oocysts/cysts has been tested using oocyst samples inactivated by three different approaches. The ability to incorporate PI staining with IFA detection provides the advantage of both detection and viabil ity determination at the same time, using the same sample.