Detection of enteric viruses and bacterial indicators in German environmental waters

Summary. A German mining lake and the supplying surface waters, which are located downstream of a sewage plant, were examined regarding their microbiological and virological quality. Between October 2002 and September 2003, specific PCR methods were used to determine the occurrence of enteric viruses in 123 water specimens drawn at different sites downstream of the waste water treatment plant and in 9 samples from the sewage plant influent. Detection rates in sewage plant effluents and surface water samples depended on sampling sites and were: 29–76% for enterovirus (EntV), 24–42% (astrovirus, AstV), 15–53% (norovirus, NV), 3–24% (rotavirus, RoV), 5–20% (hepatitis A virus, HAV) and 20% (adenovirus, AdV). AstV genome load of selected samples was between 3.7×10³ to 1.2×10⁸ genome equivalents per liter (gen.equ./l), depending on sampling location; NV average genome load ranged from 1.8×10⁴ to 9.7×10⁵gen.equ./l. Cell culture methods showed that three out of 18 PCR positive samples contained infectious EntV. Even though microbiolical parameters such as Escherichia coli, enterococci and coliphages indicated acceptable microbiological water quality, the virological data of this study suggest the possibility that surface waters may be a source for enteric viral infections.