DETECTION AND ENUMERATION OF GIARDIA CYSTS IN RIVER WATERS OF HONG-KONG BY FLOCCULATION-PERCOLL SUCROSE GRADIENT-IMMUNOFLUORESCENCE METHOD/

We have established a simple procedure for the enumeration of Giardia cysts in environmental waters of Hong Kong. The procedure involves con centrating water or sewage samples by the flocculation-percoll/sucrose gradient method followed by a modified tube method using immunofluore scent staining containing fluorescein isothiocyanate labelled anti-Gia rdia monoclonal antibodies. Enumeration of cysts was carried out using fluorescent microscopy. This procedure has the highest recovery rate (61%) compared with other conventional procedures tested (0-4%). This method was successfully applied to the detection and enumeration of Gi ardia cysts in water samples collected from two selected rivers of Hon g Kong, Shing Mun River and Lam Tsuen River. Preliminary results indic ate that water of both rivers has high counts of Giardia cysts.