||Recovery of 'Giardia' Cysts from Water: Centrifugation Versus Filtration.
Holman, B. ;
Frost, F. ;
Plan, B. ;
Fukutaki, K. ;
Jakubowski, W. ;
||Washington State Dept. of Social and Health Services, Olympia.;Health Effects Research Lab., Research Triangle Park, NC.
Giardia lamblia ;
Water pollution detection ;
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Methods for the recovery of Giardia cysts from large volume (1900 L) water samples were experimentally examined in the laboratory and applied to 22 surface water supplies around Washington state. Orlon yarn-wound filters (7 and 1 micrometer porosity) were compared, with higher cyst recovery rates observed for 1 micrometer filters. For each experiment, half the recovered material was processed through a series of screens while the other half was processed through an algae (Foerst) centrifuge. Both methods recovered cysts from 1900 L water samples containing as few as 6000 cysts, with higher recovery rates observed for the algae centrifuge. Cysts were recovered more often from surface water sources implicated in outbreaks (3 of 4) than from sources not implicated in known outbreaks (2 of 18).