Raw sewage disposal in marine waters is a common practice in many countries. This practice raises health risk concerns of possible transmission of Giardia and Cryptosporidium. Both of these protozoa have been shown to be transmitted by recreational swimming. To date no studies have determined the efficiency of their detection and concentration in marine waters. This study evaluated the efficiency of their detection in tap water and from marine waters in Hawaii with two different filter types. This study compared a polypropylene fiber cartridge filter, DPPPY (1.0 μm nominal porosity) (Cuno, Meriden, CT) which is typically used for parasite detection and the Filterite negatively charged filter (0.45μm) (Filtemp Sales, Inc., Phoenix, AZ). The latter would allow for both viruses and parasites to be concentrated simultaneously. The organisms were removed from the filter by passing the eluent through the filters in the opposite direction of collection and detected by indirect immunofluorescence antibody staining specific for Giardia and Cryptosporidium. Processing was simpler and faster with the Filterite filter and the overall efficiency for both Giardia and Cryptosporidium detection was greater. These methods are currently being used for the detection of the oocysts and cysts at bathing beaches in Hawaii impacted by marine sewage discharge.

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