Managing Wastewater in Coastal Urban Areas (1993) / Chapter Skim
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B MICROBIAL PATHOGENS IN COASTAL WATERS
B MICROBIAL PATHOGENS IN COASTAL WATERS
Pages 203-230
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Transmission of viral disease via recreational exposure to sewage contaminated waters was first documented as early as the 1950s, and is now well established (Stevenson 1953, Balarajan et al. 1991, Alexander et al.
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have been isolated from recreational waters in the absence of any discharge from a wastewater treatment plant (Rose et al.
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MICROBIAL PATHOGENS IN COASTAL WATERS TABLE B.1 Characteristics of Enteric Viruses (Bennett et al.
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Although only one TABLE B.2 Characterization of Pathogenic Protozoa in Relationship to Waterborne Diseases Giardia Cryptosporidium Entamoeba Isospora Type of Obligate Obligate Obligate enteric Obligate Protozoan enteric enteric amoebae enteric amoebae coccidian coccidian Transmission Routes Reservoirs of Infection for Man Documented Waterborne Disease in the U.S. Fecal-oral by cysts Infected animals and man, Chronic human carriers 106 outbreaks 1965-1988 >26,010 cases Fecal-oral by oocysts Infected animals and man, Chronic human carriers 3 outbreaks 1980-1988 > 13,117 cases Fecal-oral by cysts Infected animals and man, Chronic human carriers 8 outbreaks!
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The specific role of polluted coastal waters in the acquisition of these infections has been difficult to determine. While the previous bacteria all have nonmarine animal reservoirs, the noncholera Vibrio sp.
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Like the enteric viruses, the overuse of recreational sites may lead to the contamination, degradation of water quality, and disease outbreaks (CDC 1990~. Recreational outbreaks in marine waters have not been as well documented.
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suggested that animals were the source of the elevated indicator bacterial levels in storm water. An epidemiological study of recreational waters has suggested that the indicator bacteria arising from agricultural inputs are not associated with human bacterial and viral infections (Calderon et al.
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No information is available on the occurrence of enteric protozoa in marine waters. Specialized studies have been directed at specific pathogenic bacteria, but the greatest amount of information on the occurrence of pathogens in marine waters has been reported for the enteric viruses.
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Bacteria With a better appreciation of the limitations of the indicator system, new methods are being used to detect the presence of bacterial pathogens in coastal waters. In a study in Spain, Salmonella was detected in 32 percent of 256 samples collected from 21 bathing beaches along the north coast (Perales and Audicana 19891.
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· Enteric viruses persist significantly longer when compared with the bacterial indicators; · There is no qualitative or statistical association between the enteric viruses and the bacterial indicators, and · Enteric viruses have been isolated from both waters and shellfish within current bacterial standards for water quality. Table B.S gives a summary of some of the more recent studies on the occurrence of viruses in shellfish and their overlying waters in areas opened and closed for harvesting based on the bacteriological indicators.
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213 US: Cal _ _ ~ V)
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The resuspension of viruses in sediments in deep coastal waters near the outfall pipe would be insignificant due to dilution of the viruses in the large volume of overlying waters. However, in shallow coastal waters, sediments could significantly impact public health by serving as reservoirs for viral contamination of the water column resuspended by currents, storms, boats, swimmers, dredging, etc.
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2.5 E cold 0 1.6 15 3.7 30 0.58 Salmonella 4 0.96 10 - 20 0.83 - 83 37 0.7 Yersinia 4 - 37 0.6 5 - 8.5 7 Giardia 2 - 5 14 - 143 12 - 20 3.4 - 7.7 Enteric Viruses 20 0.67 -1.0 4 - 30 1.7 - 5.8 1 8 - 20 6.02 4- 15 14.02 1Time in days for 90 percent reduction in microbial levels.
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At cooler temperatures, below 10°C, the survival of enteric pathogens is enhanced. Enteric viruses may survive for months in marine waters at low temperatures.
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Much more research is needed in order to understand the fate of enteric pathogens introduced into the marine environment. The complexities of the interactions between the factors effecting survival and transport will ultimately determine the public health impact of pathogen-laden discharges to coastal waters.
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coli, total coliforms, fecal coliforms, and enterococci. The enterococci levels best predicted risk of illness and were chosen as the variable for measuring water quality and health impacts.
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Exposure depends on the initial concentration of the pathogen in the water or shellfish, processes that would decrease the numbers (i.e., wastewater treatment) , and environmental conditions that would influence microbial survival.
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I Rotavirus Poliovirus 3 100 1000 FIGURE B.3 Dose response relationships for various enteric viruses (Regli et al.
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A risk assessment model targeting infection can be used to emphasize the initial step in the chain of events that leads to the mortality associated with waterborne or foodborne pathogens. Since infec TABLE B.9 Morbidity and Mortality Rates Associated with Various Viral Pathogens (Assaad and Borecka 1977, Cherry 1981, Evans 1982, CDC 1985, Gerba et al.
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These values were used to determine virus levels in a risk assessment model to evaluate potential health impacts of consuming raw shellfish. Application of a Virus Risk Model to Characterize Risks from Consuming Shellfish It is well known that infectious hepatitis and viral gastroenteritis are caused by consumption of raw or, in some cases, cooked clams and oysters.
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223 o oo Ct 1 4 _ C~ s~ ._ o ~ _ Q Ct V)
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The risk of becoming infected with the exposure to even one virus was estimated at between 10-i to 10-2. SUMMARY OF SHELLFISH AND RECREATIONAL MICROBIOLOGIC RISKS Acceptable recreational risks based on indicator bacterial levels and epidemiological studies have suggested an acceptable risk level of 8 x 10-3 (Cabelli et al.
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Coastal water temperatures will influence the survival of the pathogens and the potential for regrowth of the coliforms. The warmer waters in the Gulf and off the southern Atlantic states may enhance the inactivation rates for pathogens while enhancing the potential for inputs of coliforms that have grown in fresh water environments.
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See Appendix D for discussion of wastewater treatment options, disinfection procedures, and combined sewer overflow controls. Despite requirements that shellfish harvesting waters must meet established bacterial indicator standards and sanitary survey criteria, disease outbreaks due to consumption of contaminated shellfish continue to occur in the United States.
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1983. A marine recreational water quality criterion consistent with indicator concepts and risk analysis.
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federal bacteriological water quality criteria governing marine recreational waters. Research Journal of the WPCF 63:259265.
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undated. Quantitative risk assessment for viral contamination of shellfish and coastal waters.
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1983. Enteric bacterial and viral pathogens and indicator bacteria in hard shell clams.
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