Methods for the detection of viable rotaviruses and rotavirus antigen in water were developed and compared. The methods included laboratory-developed enzyme-linked immunosorbent assays (ELISAs) with chromogenic and luminescent substrates, commercial Rotazyme and Enzygnost ELISAs, and an indirect immunofluorescent assay. Of the methods tested, the immunofluorescent assay and the Enzygnost ELISA were the most sensitive for the simian rotavirus SA-li. All of the methods were positive for human rotavirus from clinical specimens. Seeded SA-li rotavirus was concentrated from water by adsorption to and elution from Zeta Plus ifiters followed by organic flocculation. Interference with the assays by components of the wastewater concentrates was minimal for the ELISAs, although the undiluted organic flocs were cytotoxic for the immunofluorescent assay. A survey of Jerusalem wastewater was carried out over the course of 1 year, and samples were assayed for rotaviruses and enteroviruses. Although enteroviruses were found in almost all of the samples, all samples were negative for rotaviruses. The concentration of rotaviruses in the wastewater was thus below the detection limit of the methods used.
The digestive tracts of tilapia reared in commercial fish ponds with animal manure and/or municipal wastewater generally were contaminated with the fecal indicators E.coli and enterococci to levels greater than those in the environmental water. When the indicator densitites in the water were sufficiently high, the liver and muscle tissue also became contaminated, albeit to much lower levels. Thermotolerant aeromonas were recovered from the environmental water and fish tissues at levels 2-4 logs higher than those of the fecal indicators. Accumulation of the indicators in the tissues of the naturally contaminated (pond) fish generally was greater than that in the artificially contaminated fish.
The indicator levels in the tissues did not appreciably decrease when the pond-reared fish were maintained for 5-8 days under starvation conditions in tanks containing water which was not exchanged. However, the E.coli and virus levels in the tissues of experimentally contaminated tilapia were appreciably and significantly reduced under the same conditions. The results point out the limited value of conventional “purification” methods as applied to tilapia reared in fecally fertilized waters and of data obtained from studies with experimental animals. Since fish are cooked prior to consumption, the major public health concern could be the risk of Aeromonas wound infections among individuals who handle and process fish.
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