The principal objective of this research was the development of a sensitive, standardized method of determining whether or not Giardia cysts are viable. The availability of such a method is necessary to determine the effect of chemical and physical agents on the viability of these organisms in water. Using cysts collected from an asymptomatic human carrier, a method for inducing excystation was developed and optimized with regard to pH, time of acid exposure, incubation temperature and excystation medium. The method was applied in determining the effects of cyst storage in water at various temperatures on cyst survival as determined by the cultural excystation method and eosin dye exclusion. The results indicate that cyst survival time decreased with increasing temperatures above 0C. Freezing and thawing resulted in almost complete loss of viability.

"EPA 600-2-79-063." "July 1979." Cover title. Prepared for U.S. Environmental Protection Agency, Office of Research and Development, Municipal Environmental Research Laboratory, Cincinnati, Ohio, under grant no. R804898. Includes bibliographical references (pages 24-27).