Indicators Of Viral Pollution Research Articles

The Utility of Dreissena polymorpha for Assessing the Viral Contamination of Rivers by Measuring the Accumulation of F-Specific RNA Bacteriophages

River water that receives treated wastewater can be contaminated by pathogens including enteric viruses due to fecal pollution, which may represent an important public health hazard. There is a great diversity of enteric viruses and fecal bacteriophages, especially F-specific RNA bacteriophages (FRNAPHs), are commonly proposed as indicators of viral pollution due to a variety of characteristics such as their structural similarities to the main enteric viruses, their high concentrations in raw wastewater and their environmental survival rate, which is better than other cultivable enteric viruses. However, evaluating the viral contamination of water on the basis of FRNAPH concentration levels continues to present a challenge. This is because the quality of detection is strongly dependent on the quantity of viral particles, high spatio-temporal variabilities and the physico-chemical conditions of the water during sampling. To overcome these limitations, the present study aims to evaluate whether the bivalve mollusk Dreissena polymorpha (zebra mussel) could be considered a suitable experimental model for assessing the viral contamination of rivers. In order to determine this, the capacity of D. polymorpha to accumulate FRNAPHs and assimilate them into their soft tissue was studied. This provided a proof of concept for the use of D. polymorpha to evaluate the viral contamination of surface water. Two experiments were conducted: (1) an in situ experiment to confirm that zebra mussels naturally accumulated FRNAPHs and (2) a laboratory experiment to determine the accumulation and depuration kinetics of FRNAPHs in D. polymorpha tissue. The study highlights the capacity of the mussels to accumulate infectious FRNAPHs both on a laboratory scale under controlled conditions as well as in situ at different sites that are representative of different bodies of water. An analysis of the mussels’ soft tissue showed that they were capable of reflecting the water’s contamination level very quickly (within less than 24 h). Moreover, the soft tissue retained the viral load much longer than the water due to a low depuration rate. The analysis of FRNAPH concentrations in mussels exposed in situ suggested that there were differences in contamination levels between sites. These preliminary results underline the potential utility of zebra mussels in assessing viral contamination by measuring the accumulation of FRNAPHs in their tissue. This may ultimately enable stakeholders to use zebra mussels as a means of monitoring viral pollution in surface water.

Interaction of human adenoviruses and coliphages with kaolinite and bentonite

Human adenoviruses (hAdVs) are pathogenic viruses responsible for public health problems worldwide. They have also been used as viral indicators in environmental systems. Coliphages (e.g., MS2, ΦX174) have also been studied as indicators of viral pollution in fecally contaminated water. Our objective was to evaluate the distribution of three viral fecal indicators (hAdVs, MS2, and ΦΧ174), between two different phyllosilicate clays (kaolinite and bentonite) and the aqueous phase. A series of static and dynamic experiments were conducted under two different temperatures (4, 25°C) for a time period of seven days. HAdV adsorption was examined in DNase I reaction buffer (pH=7.6, and ionic strength (IS)=1.4mM), whereas coliphage adsorption in phosphate buffered saline solution (pH=7, IS=2mM). Moreover, the effect of IS on hAdV adsorption under static conditions was evaluated. The adsorption of hAdV was assessed by real-time PCR and its infectivity was tested by cultivation methods. The coliphages MS2 and ΦΧ174 were assayed by the double-layer overlay method. The experimental results have shown that coliphage adsorption onto both kaolinite and bentonite was higher for the dynamic than the static experiments; whereas hAdV adsorption was lower under dynamic conditions. The adsorption of hAdV increased with decreasing temperature, contrary to the results obtained for the coliphages. This study examines the combined effect of temperature, agitation, clay type, and IS on hAdV adsorption onto clays. The results provide useful new information on the effective removal of viral fecal indicators (MS2, ΦX174 and hAdV) from dilute aqueous solutions by adsorption onto kaolinite and bentonite. Factors enabling enteric viruses to penetrate soils, groundwater and travel long distances within aquifers are important public health issues. Because the observed adsorption behavior of surrogate coliphages MS2 and ΦΧ174 is substantially different to that of hAdV, neither MS2 nor ΦΧ174 is recommended as a suitable model for adenovirus.

Detection of enterovirus in environmental waters: A new optimized method compared to commercial real-time RT-qPCR kits

Despite the progress in water and wastewater treatment technologies, waterborne diseases are still a major concern of public health. In the reported water-related outbreaks, viruses constitute one of the main causal agents. Enteroviruses are one of the most viruses monitored in water and are often used as an indicator of viral pollution. Isolation and identification of this virus are now regularly based on molecular tools. However published or commercial protocols for detection of these viruses in water are frequently lacking of validation processes and performance evaluation in such complex samples. A method for enterovirus detection in environmental water has been developed, its performance has been evaluated and compared with several commercial kits.The sensitivity of commercial methods in clinical samples, ranged between 89% and 100%, while the sensitivity in seeded environmental matrices fell between 16% and 91%. This method showed the best performance in environmental samples and was subsequently applied on surface and treated wastewater. The results showed the large dissemination of enteroviruses in an urbanized river. The results also emphasized the importance of good knowledge of the method's limits for its utilization in environmental samples in order to minimize false negatives and to avoid underestimating viral concentration.

The development of management strategies for control of virological quality in oysters

This laboratory has previously described the development of a PCR method for the detection of small round structured viruses (SRSVs) in shellfish and the use of male-specific RNA bacteriophages as “viral” indicators to predict the occurrence and behaviour of such viruses in shellfish. We now describe the application of these procedures to monitor oyster harvesting areas, shellfish treatment processes and products sold to the consumer. Oysters are traditionally consumed raw and can be treated to enable them to meet the legislative end-product standard of <230 E coli/100g. Treatment options include purification (depuration) in tanks of clean seawater or relaying in clean seawater for a suitable period. These procedures are effective for enabling shellfish compliance with the existing bacterial end product standard but do not guarantee viral protection for the consumer. This study initially investigates the efficiency of these treatment processes for reducing viral contamination in sewage-contaminated oysters. Initial levels of viral pollution in oysters were found to be critical to the success of post-harvest treatment processes. Additionally, the success of depuration and relaying for virus removal was found to be dependent on the duration of the process and on factors affecting shellfish metabolic activity such as the water temperature. We demonstrate that by using male-specific RNA bacteriophage as an indicator of viral pollution combined with SRSV monitoring it is possible to derive management strategies for more effective control of the virological quality of oysters. Male-specific RNA bacteriophage monitoring of final products prior to sale to the consumer provided an effective quality control mechanism. We discuss the combined use of these new monitoring tools for more effective management of the virological quality of oysters sold to the consumer.

In Situ Survival of Indicator Bacteria, MS-2 Phage and Human Pathogenic Viruses in River Water

Previous studies of microbial behaviour in situ have used dialysis sacs and diffusion chambers to permit contact of contained microorganisms with the external aqueous milieu. Their main limitation is a slow response to changes in water quality, preventing adequate simulation of field conditions. This study used the ECODYNE system™, a new device responsive to real time changes in water quality. It consists of a hollow fibre membrane module and fluid reservoir which separates the test microorganisms from the external environment. Use of a mixture of Escherichia coli, Enterococcus dwans, MS-2 phage, poliovirus type 1 (Sabin) and hepatitis A virus (HM-175) allowed direct comparison of their survival in river water under identical conditions over a period of at least 24 hours. The results can be summarised as follows: a) survival patterns of E. coli in nutrient rich river water were highly variable, b) a ten-fold or greater increase in numt)ers of E. coli was sometimes observed in twth latwratory and field tests, c) no regrowth was ever observed with E. durons, and its titre declined faster than that of E. coli, and d) over the first 24 hours, the phage survival was similar to that of the human pathogenic viruses. The observations regarding the variable survival of E. coli and its potential for regrowth raise questions about its suitability as a water quality indicator. MS-2 phage shows promise as an indicator of viral pollution, but requires further study. The ECODYNE system proved highly suitable in this study, and shows potential for other environmental interaction/environmental fate studies including ecotoxicological investigations and monitoring.

Contents of volume 46

This study examined the survival of indigenous coliphages (serving as indicators of viral pollution) during operation of a field-scale (1140 m3 day−1) water hyacinth (Eichhornia crassipes) treatment system in San Diego, CA. At a hydraulic residence time of 4.4 days, about 20% of the indigenous coliphages could be recovered after flow through the water hyacinth pond. The decay rates of coliphages in stagnant mesocosms with the water hyacinth plant (k = −0.015 h−1) and in wastewater incubated in dialysis bags suspended in the pond (k = −0.019 h−) were both greater than the value for coliphage decay in the operational water hyacinth system (k = −0.014 h−1), indicating that filtration/adsorption of coliphage by the root matrix is not a major contributor to coliphage reduction. Coliphage decay in mesocosms without plants was more rapid (k = −0.024 h−1) than in planted mesocosms (k = −0.015 h−1) and covered mesocosms (k = −0.011 h−1). These results suggest the important role of sunlight in coliphage inactivation, and reflect the fact that coliphage decay in the presence of the plant is slower than the natural decay rate in wastewater without plants.

Fate of coliphage during wastewater treatment by water hyacinth ( Eichhornia crassipes)

This study examined the survival of indigenous coliphages (serving as indicators of viral pollution) during operation of a field-scale (1140 m 3 day −1) water hyacinth ( Eichhornia crassipes) treatment system in San Diego, CA. At a hydraulic residence time of 4.4 days, about 20% of the indigenous coliphages could be recovered after flow through the water hyacinth pond. The decay rates of coliphages in stagnant mesocosms with the water hyacinth plant ( k = −0.015 h −1) and in wastewater incubated in dialysis bags suspended in the pond ( k = −0.019 h −) were both greater than the value for coliphage decay in the operational water hyacinth system ( k = −0.014 h −1), indicating that filtration/adsorption of coliphage by the root matrix is not a major contributor to coliphage reduction. Coliphage decay in mesocosms without plants was more rapid ( k = −0.024 h −1) than in planted mesocosms ( k = −0.015 h −1) and covered mesocosms ( k = −0.011 h −1). These results suggest the important role of sunlight in coliphage inactivation, and reflect the fact that coliphage decay in the presence of the plant is slower than the natural decay rate in wastewater without plants.

Fate of viruses in artificial wetlands.

Little is known about the ability of wetlands to remove disease-causing viruses from municipal wastewater. In this study we examined the survival of several indicators of viral pollution (indigenous F-specific bacteriophages, seeded MS2 bacteriophage, and seeded human poliovirus type 1) applied in primary municipal wastewater to artificial wetland ecosystems. Only about 1% of the indigenous F-specific RNA bacteriophages survived flow through the vegetated wetland beds at a 5-cm-day-1 hydraulic application rate during the period from June through December 1985. The total number of indigenous F-specific bacteriophages (F-specific RNA and F-specific DNA phages) was also reduced by about 99% by wetland treatment, with the mean inflow concentration over the period of an entire year reduced from 3,129 to 33 PFU ml-1 in the outflow of a vegetated bed and to 174 PFU ml-1 in the outflow of an unvegetated bed. Such superior treatment by the vegetated bed demonstrates the significant role of higher aquatic plants in the removal process. Seeded MS2 bacteriophage and seeded poliovirus were removed more efficiently than were the indigenous bacteriophages, with less than 0.2% of MS2 and 0.1% of the poliovirus surviving flow at the same hydraulic application rate. The decay rate (k) of MS2 in a stagnant wetlands (k = 0.012 to 0.028 h-1) was lower than that for flowing systems (k = 0.44 to 0.052 h-1), reflecting the enhanced capacity for filtration or adsorption of viruses by the root-substrate complex (and associated biofilm).(ABSTRACT TRUNCATED AT 250 WORDS)

Human enteroviruses in marine sediments near a sewage outfall on the Otago Coast

Abstract Sediment and beach sand samples from around a sewer outfall were collected and tested for the presence of enteroviruses and faecal coliforms. Enteroviruses were recovered from 5 of 14 samples collected on three different occasions. Enteroviruses were recovered from two samples in which faecal coliform levels were low. These results suggest that the faecal coliform test may not be a reliable indicator of viral pollution. Virus types recovered were Poliovirus 2, Coxsackievirus B4 and B5, and a number of isolates unable to be identified using the Lim Benyesh‐Melnick pooled antisera.

Relative chlorine resistance of poliovirus I and coliphages f2 and T 2 in water.

Phage f2 is markedly more resistant to chlorine in water than either poliovirus or coliphage T(2). Its potential use as an indicator of viral pollution is suggested.

Relative Chlorine Resistance of Poliovirus I and Coliphages f2 and T2 in Water

Phage f2 is markedly more resistant to chlorine in water than either poliovirus or coliphage T(2). Its potential use as an indicator of viral pollution is suggested.