Giardia Cysts in Treated Wastewater Effluents: Are They Infective?

April Garcia, William Yanko, Glenda Batzer and Giovanni Widmer

The infectivity of Giardia lamblia cysts recovered in primary- and tertiary-treated effluents was assessed in Mongolian gerbils (Meriones unguiculatus). Infections in gerbils inoculated with cysts from primary effluent concentrates demonstrated the presence of infectious G. lamblia cysts. No infectious cysts were detected by this method in concentrates of tertiary-treated effluents. It is apparent from this study that determination of cyst concentrations without viability or infectivity assessment may significantly over-estimate the potential health risks associated with protozoan cysts in wastewater effluents. Water Environ. Res. (2000) 74, 541

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