Viruses and bivalve shellfish

Oceans and Human Health (OHH): a European perspective from the Marine Board of the European Science Foundation (Marine Board-ESF)

The oceans and coastal seas provide mankind with many benefits including food for around a third of the global population, the air that we breathe and our climate system which enables habitation of much of the planet. However, the converse is that generation of natural events (such as hurricanes, severe storms and tsunamis) can have devastating impacts on coastal populations, while pollution of the seas by pathogens and toxic waste can cause illness and death in humans and animals. Harmful effects from biogenic toxins produced by algal blooms (HABs) and from the pathogens associated with microbial pollution are also a health hazard in seafood and from direct contact with water. The overall global burden of human disease caused by sewage pollution of coastal waters has been estimated at 4 million lost person-years annually. Finally, the impacts of all of these issues will be exacerbated by climate change. A holistic systems approach is needed. It must consider whole ecosystems, and their sustainability, such as integrated coastal zone management, is necessary to address the highly interconnected scientific challenges of increased human population pressure, pollution and over-exploitation of food (and other) resources as drivers of adverse ecological, social and economic impacts. There is also an urgent and critical requirement for effective and integrated public health solutions to be developed through the formulation of politically and environmentally meaningful policies. The research community required to address "Oceans & Human Health" in Europe is currently very fragmented, and recognition by policy makers of some of the problems, outlined in the list of challenges above, is limited. Nevertheless, relevant key policy issues for governments worldwide include the reduction of the burden of disease (including the early detection of emerging pathogens and other threats) and improving the quality of the global environment. Failure to effectively address these issues will impact adversely on efforts to alleviate poverty, sustain the availability of environmental goods and services and improve health and social and economic stability; and thus, will impinge on many policy decisions, both nationally and internationally. Knowledge exchange (KE) will be a key element of any ensuing research. KE will facilitate the integration of biological, medical, epidemiological, social and economic disciplines, as well as the emergence of synergies between seemingly unconnected areas of science and socio-economic issues, and will help to leverage knowledge transfer across the European Union (EU) and beyond. An integrated interdisciplinary systems approach is an effective way to bring together the appropriate groups of scientists, social scientists, economists, industry and other stakeholders with the policy formulators in order to address the complexities of interfacial problems in the area of environment and human health. The Marine Board of the European Science Foundation Working Group on "Oceans and Human Health" has been charged with developing a position paper on this topic with a view to identifying the scientific, social and economic challenges and making recommendations to the EU on policy-relevant research and development activities in this arena. This paper includes the background to health-related issues linked to the coastal environment and highlights the main arguments for an ecosystem-based whole systems approach.

Susceptibility of murine norovirus and hepatitis A virus to electron beam irradiation in oysters and quantifying the reduction in potential infection risks

Consumption of raw oysters is an exposure route for human norovirus (NoV) and hepatitis A virus (HAV). Therefore, efficient postharvest oyster treatment technology is needed to reduce public health risks. This study evaluated the inactivation of HAV and the NoV research surrogate, murine norovirus-1 (MNV-1), in oysters (Crassostrea virginica) by electron beam (E-beam) irradiation. The reduction of potential infection risks was quantified for E-beam irradiation technology employed on raw oysters at various virus contamination levels. The E-beam dose required to reduce the MNV and HAV titer by 90% (D(10) value) in whole oysters was 4.05 (standard deviations [SD], ±0.63) and 4.83 (SD, ±0.08) kGy, respectively. Microbial risk assessment suggests that if a typical serving of 12 raw oysters was contaminated with 10(5) PFU, a 5-kGy treatment would achieve a 12% reduction (from 4.49 out of 10 persons to 3.95 out of 10 persons) in NoV infection and a 16% reduction (from 9.21 out of 10 persons to 7.76 out of 10 persons) in HAV infections. If the serving size contained only 10(2) PFU of viruses, a 5-kGy treatment would achieve a 26% reduction (2.74 out of 10 persons to 2.03 out of 10 persons) of NoV and 91% reduction (2.1 out of 10 persons to 1.93 out of 100 persons) of HAV infection risks. This study shows that although E-beam processing cannot completely eliminate the risk of viral illness, infection risks can be reduced.

Elevated post-transfusion serum transaminase values associated with a highly significant trend for increasing prevalence of anti-Vesivirus antibody in Korean patients

A highly significant increase in anti-Vesivirus (family Caliciviridae) antibody prevalence, along the axis from healthy blood donors; donors with elevated transaminase; patients with clinical hepatitis; and patients with post-transfusion/dialysis hepatitis, has been reported in human sera from the USA and Europe. Asian samples have now been tested retrospectively using serology and enzyme immunoassay (EIA) with a Vesivirus partial-capsid antigen expressed as a fusion protein. Anti-vesiviral antibodies were measured by optical densities (OD(650)) and compared in patients separated by age, gender and Groups A-F as follows: Control Group A, an Experimental Group B, which was divided further into Group C, patients with elevated enzymes (alanine transaminase (ALT), aspartate transaminase (AST), and γ-glutamyl transpeptidase (γ-GT); Group D, patients receiving transfused blood; Group E, patients with high enzyme levels after transfusion; and Group F, hepatitis B and C positive patients. Using multivariate logistic regression analyses, a significantly greater proportion of patients receiving transfusion(s), were positive for anti-Vesivirus antibody compared with non-transfused patients (P = 0.008; OR: 3.86, 95% CI: 1.43-10.43). Also, anti-Vesivirus antibody was significantly associated with elevated biochemical liver function tests: ALT ≥ 20 IU or AST ≥ 120 IU (P = 0.017; OR: 4.23, 95% CI: 1.30-13.80). In the blood transfusion group, anti-Vesivirus antibody was significantly correlated with high enzyme levels (ALT, P = 0.018; AST, P = 0.010; γ-GT, P = 0.020). These data provide serologic evidence of vesiviral transfusion-transmission-associated disease, which could include infection of any organ system where cytopathology resulted in high levels of either ALT or AST.

Shellfish-borne viral outbreaks: a systematic review

Investigations of disease outbreaks linked to shellfish consumption have been reported in the scientific literature; however, only few countries systematically collate and report such data through a disease surveillance system. We conducted a systematic review to investigate shellfish-borne viral outbreaks and to explore their distribution in different countries, and to determine if different types of shellfish and viruses are implicated. Six databases (Medline, Embase, Scopus, PubMed, Eurosurveillance Journal and Spingerlink electronic Journal) and a global electronic reporting system (ProMED) were searched from 1980 to July 2012. About 359 shellfish-borne viral outbreaks, alongside with nine ProMED reports, involving shellfish consumption, were identified. The majority of the reported outbreaks were located in East Asia, followed by Europe, America, Oceania, Australia and Africa. More than half of the outbreaks (63.6 %) were reported from Japan. The most common viral pathogens involved were norovirus (83.7 %) and hepatitis A virus (12.8 %). The most frequent type of consumed shellfish which was involved in outbreaks was oysters (58.4 %). Outbreaks following shellfish consumption were often attributed to water contamination by sewage and/or undercooking. Differences in reporting of outbreaks were seen between the scientific literature and ProMED. Consumption of contaminated shellfish represents a risk to public health in both developed and developing countries, but impact will be disproportionate and likely to compound existing health disparities.

Trends in the levels of Escherichia coli in commercially harvested bivalve shellfish from England and Wales, 1999-2008

Temporal trends in Escherichia coli concentrations in bivalve shellfish were examined using data collected from 57 production areas around the coast of England and Wales during 1999-2008. Downward trends were detected in annual geometric means of E. coli in shellfish from 12% of the sampling points. The percentage of class B areas (E. coli ≤ 4600/100 g shellfish in 90% of samples) increased from 69% to 86% during the 10-year period. The improvement in the microbial quality of shellfish is associated with sewerage improvement schemes largely implemented during 2000-2005. Upward trends were detected in 9% of the points. The causes of these increases are not known. It is recommended that quantitative sanitary profiling of shellfish waters and cost-benefit appraisal over long-term planning horizons are considered as part of sewerage investment programmes under the Water Framework Directive. This would allow greater scope to secure protection and improvement of shellfish water quality.

Combined effect of lime (Citrus aurantitolia) and drying on reducing bacteria of public health significance in Edible Oyster (Crassostrea madrasensis)

Combined effect of lime and drying on bacteria of public health significance in Edible Oyster (Crassostrea madrasensis) from Munambam coastal belt (Kerala, India) were studied (without depuration). Samples were examined for Total Plate Count (TPC), Staphylococcus aureus (hygiene indicator), Total coliforms, Faecal coliforms, Escherichia coli, (faecal indicator) Faecal Streptococci (faecal indicator), Salmonella, Vibrio cholera and Listeria monocytogenes. The fresh oyster meat though did not confirm to the specifications laid by National shellfish sanitation programme (NSSP), after treatment with lime with and without drying found to show significant reduction in counts and meet the required standards. Prevalence of faecal indicators in the fresh sample indicated faecal pollution in the area. The isolation of potentially pathogenic bacteria, V. parahaemolyticus in fresh sample indicates high risk of people consuming and handling oysters in raw and semi processed form and also it may lead to cross contamination. The present study indicates that treatment with natural organic product like lime and simple preservation technique, drying can effectively reduce the bacterial load. The study also revealed that TPC of water and soil collected from the site from where oysters were collected was less than from the meat.

Pressure inactivation of Tulane virus, a candidate surrogate for human norovirus and its potential application in food industry

Human norovirus (HuNoV) is the leading causative agent for foodborne disease. Currently, studies of HuNoV usually rely on surrogates such as murine norovirus (MNV) due to the lack of a suitable cell culture system and a small animal model for HuNoV. Tulane virus (TV), a monkey calicivirus, is a cultivable enteric calicivirus that not only recognizes the same receptors as HuNoV, but is also genetically closely related to HuNoV. In this study, we determined the pH stability of TV and MNV-1, as well as the effect of high hydrostatic pressure (HHP) on inactivating both viruses in aqueous media, blueberries and oysters. We demonstrated that both TV and MNV-1 were very stable under an acidic environment. They were more resistant to pressure at an acidic environment than at neutral pH. Pressure treatment of 600 MPa for 2 min at different temperatures (4, 21 and 35 °C) barely caused any reduction of TV, as well as MNV-1, on un-wetted (dry) blueberries. However, both TV and MNV-1 on blueberries were successfully inactivated by a pressure of ≤400 MPa when blueberries were immersed in phosphate-buffered saline during HHP. Pressure inactivation of both TV and MNV-1 in blueberries and oysters increased as sample temperature decreased in the order of 4>21>35 °C. TV was more sensitive to pressure than MNV-1 for the three matrices tested, culture media, blueberries and oysters. This study provides important information on the use of TV as a surrogate for HuNoV study. Results obtained from this study lay a foundation for designing effective HHP treatments for inactivation of HuNoV in high-risk foods such as berries and oysters.

Comparing human norovirus surrogates: murine norovirus and Tulane virus

Viral surrogates are widely used by researchers to predict human norovirus behavior. Murine norovirus (MNV) is currently accepted as the best surrogate and is assumed to mimic the survival and inactivation of human noroviruses. Recently, a new calicivirus, the Tulane virus (TV), was discovered, and its potential as a human norovirus surrogate is being explored. This study aimed to compare the behavior of the two potential surrogates under varying treatments of pH (2.0 to 10.0), chlorine (0.2 to 2,000 ppm), heat (50 to 75°C), and survival in tap water at room (20°C) and refrigeration (4°C) temperatures for up to 30 days. Viral infectivity was determined by the plaque assay for both MNV and TV. There was no significant difference between the inactivation of MNV and TV in all heat treatments, and for both MNV and TV survival in tap water at 20°C over 30 days. At 4°C, MNV remained infectious over 30 days at a titer of approximately 5 log PFU/ml, whereas TV titers decreased significantly by 5 days. MNV was more pH stable, as TV titers were reduced significantly at pH 2.0, 9.0, and 10.0, as compared with pH 7.0, whereas MNV titers were only significantly reduced at pH 10.0. After chlorine treatment, there was no significant difference in virus with the exception of at 2 ppm, where TV decreased significantly compared with MNV. Compared with TV, MNV is likely a better surrogate for human noroviruses, as MNV persisted over a wider range of pH values, at 2 ppm of chlorine, and without a loss of titer at 4°C.

New approaches in microbial pathogen detection

Viruses are common causes of foodborne outbreaks. Viral diseases have low fatality rates but transmission to humans via food is important due to the high probability of consuming fecally contaminated food or water because of poor food handling. Because of the low infectious doses of some foodborne viruses, there is a need for standardization and the development of new sensitive methods for detecting viruses. The focus is on molecular and non-molecular approaches, and emerging methods for the detection of foodborne viruses. The detection of noroviruses, hepatitis A and E viruses, rotaviruses and adenoviruses will be discussed. The chapter will conclude with insights into future research directions.

Harmonised investigation of the occurrence of human enteric viruses in the leafy green vegetable supply chain in three European countries

Numerous outbreaks have been attributed to the consumption of raw or minimally processed leafy green vegetables contaminated with enteric viral pathogens. The aim of the present study was an integrated virological monitoring of the salad vegetables supply chain in Europe, from production, processing and point-of-sale. Samples were collected and analysed in Greece, Serbia and Poland, from 'general' and 'ad hoc' sampling points, which were perceived as critical points for virus contamination. General sampling points were identified through the analysis of background information questionnaires based on HACCP audit principles, and they were sampled during each sampling occasion where as-ad hoc sampling points were identified during food safety fact-finding visits and samples were only collected during the fact-finding visits. Human (hAdV) and porcine (pAdV) adenovirus, hepatitis A (HAV) and E (HEV) virus, norovirus GI and GII (NoV) and bovine polyomavirus (bPyV) were detected by means of real-time (RT-) PCR-based protocols. General samples were positive for hAdV, pAdV, HAV, HEV, NoV GI, NoV GII and bPyV at 20.09 % (134/667), 5.53 % (13/235), 1.32 % (4/304), 3.42 % (5/146), 2 % (6/299), 2.95 % (8/271) and 0.82 % (2/245), respectively. Ad hoc samples were positive for hAdV, pAdV, bPyV and NoV GI at 9 % (3/33), 9 % (2/22), 4.54 % (1/22) and 7.14 % (1/14), respectively. These results demonstrate the existence of viral contamination routes from human and animal sources to the salad vegetable supply chain and more specifically indicate the potential for public health risks due to the virus contamination of leafy green vegetables at primary production.

Multiple Clusters of Norovirus among Shellfish Consumers Linked to Symptomatic Oyster Harvesters

We describe the investigation of a norovirus outbreak associated with raw oyster consumption affecting 36 people in British Columbia, Canada, in 2010. Several genotypes were found in oysters, including an exact sequence match to clinical samples in regions B and C of the norovirus genome (genogroup I genotype 4). Traceback implicated a single remotely located harvest site probably contaminated by ill shellfish workers during harvesting activities. This outbreak resulted in three recalls, one public advisory, and closure of the harvest site.

Modified Atmosphere Packaging Technology of Fresh and Fresh-cut Produce and the Microbial Consequences-A Review

Modified atmosphere packaging (MAP) technology offers the possibility to retard the respiration rate and extend the shelf life of fresh produce, and is increasingly used globally as value adding in the fresh and fresh-cut food industry. However, the outbreaks of foodborne diseases and emergence of resistant foodborne pathogens in MAP have heightened public interest on the effects of MAP technology on the survival and growth of pathogenic organisms. This paper critically reviews the effects of MAP on the microbiological safety of fresh or fresh-cut produce, including the role of innovative tools such as the use of pressurised inert/noble gases, predictive microbiology and intelligent packaging in the advancement of MAP safety. The integration of Hazard Analysis and Critical Control Points-based programs to ensure fresh food quality and microbial safety in packaging technology is highlighted.

Virus hazards from food, water and other contaminated environments

Numerous viruses of human or animal origin can spread in the environment and infect people via water and food, mostly through ingestion and occasionally through skin contact. These viruses are released into the environment by various routes including water run-offs and aerosols. Furthermore, zoonotic viruses may infect humans exposed to contaminated surface waters. Foodstuffs of animal origin can be contaminated, and their consumption may cause human infection if the viruses are not inactivated during food processing. Molecular epidemiology and surveillance of environmental samples are necessary to elucidate the public health hazards associated with exposure to environmental viruses. Whereas monitoring of viral nucleic acids by PCR methods is relatively straightforward and well documented, detection of infectious virus particles is technically more demanding and not always possible (e.g. human norovirus or hepatitis E virus). The human pathogenic viruses that are most relevant in this context are nonenveloped and belong to the families of the Caliciviridae, Adenoviridae, Hepeviridae, Picornaviridae and Reoviridae. Sampling methods and strategies, first-choice detection methods and evaluation criteria are reviewed.

Presence of hepatitis E RNA in mussels used as bio-monitors of viral marine pollution

Mussels (Mytilus galloprovincialis), collected from a harvesting area approved by European Community Regulation, were transplanted to four polluted sites located in the Northwestern Mediterranean area (Tuscany). They were used as bio-monitors to test the quality of the marine water pollution. At different times after the transplantation, mussels were withdrawn and tested for presence of phages and enteric viruses by molecular tests. 52.4% of the transplanted mussel samples were positive for at least one enteric virus. Hepatitis A virus (HAV) was identified in each site (17/37; 45.9%). Three samples were positive for hepatitis E virus (HEV) (8.1%) and two (5.4%) for norovirus (NoV) genogroup I. Coliphages and RYC 2056 phages were detected in all sites, while HSP 40 phages were detected in three sites. Results demonstrate the ability of transplanted mussels in accumulating and retaining different species of enteric microorganisms. Their utility as bio-monitor organisms enables testing for viral marine pollution.

Two-year systematic study to assess norovirus contamination in oysters from commercial harvesting areas in the United Kingdom

The contamination of bivalve shellfish with norovirus from human fecal sources is recognized as an important human health risk. Standardized quantitative methods for the detection of norovirus in molluscan shellfish are now available, and viral standards are being considered in the European Union and internationally. This 2-year systematic study aimed to investigate the impact of the application of these methods to the monitoring of norovirus contamination in oyster production areas in the United Kingdom. Twenty-four monthly samples of oysters from 39 United Kingdom production areas, chosen to represent a range of potential contamination risk, were tested for norovirus genogroups I and II by using a quantitative real-time reverse transcription (RT)-PCR method. Norovirus was detected in 76.2% (643/844) of samples, with all sites returning at least one positive result. Both prevalences (presence or absence) and norovirus levels varied markedly between sites. However, overall, a marked winter seasonality of contamination by both prevalence and quantity was observed. Correlations were found between norovirus contamination and potential risk indicators, including harvesting area classifications, Escherichia coli scores, and environmental temperatures. A predictive risk score for norovirus contamination was developed by using a combination of these factors. In summary, this study, the largest of its type undertaken to date, provides a systematic analysis of norovirus contamination in commercial oyster production areas in the United Kingdom. The data should assist risk managers to develop control strategies to reduce the risk of human illness resulting from norovirus contamination of bivalve molluscs.

cDNA microarray analysis of disk abalone genes in gills and hemocytes after viral hemorrhagic septicemia virus (VHSV) challenge

A disk abalone Haliotis discus discus 4.2 K cDNA microarray was designed by selecting abalone expressed sequence tags (ESTs). Transcriptional profiles in gills and hemocytes were analyzed upon abalone challenged with viral hemorrhagic septicemia virus (VHSV) in order to select candidates for screening of immune response genes. Among the 4188 genes analyzed, 280 (6.6%) transcripts were changed their expression level in gills and hemocytes against VHSV challenge compared to control animals. Total of 88 and 65 genes were up-regulated in gills and hemocytes, respectively. These genes can be grouped under various immune-functional categories such as transcription factors (Krüppell-like factor; ETS-family transcription factor), inflammatory and apoptosis related genes (TNF superfamily members, Fas ligand), IFN regulatory proteins (IFN-44 like, interferon gamma-inducible lysosomal thiol reductase) and detoxification proteins (glutathione peroxidase). In contrast, 25 and 102 genes were shown down-regulation in gills and hemocytes, respectively. Among the differentially expressed transcripts, considerably higher numbers of ESTs were represented as either hypothetical (unknown) proteins or no GenBank match suggesting those may be novel genes associated with internal defense of abalone.

Occurrence of human enteric viruses in commercial mussels at retail level in three European countries

In this study, the prevalence of different enteric viruses in commercial mussels was evaluated at the retail level in three European countries (Finland, Greece and Spain). A total of 153 mussel samples from different origins were analysed for human norovirus (NoV) genogroups I and II, hepatitis A virus (HAV) and hepatitis E virus (HEV). Human adenovirus (HAdV) was also tested as an indicator of human faecal contamination. A full set of controls (such as sample process control, internal amplification controls, and positive and negative controls) were implemented during the process. The use of a sample process control allowed us to calculate the efficiencies of extraction, which ranged from 79 to 0.5 %, with an average value of 10 %. Samples were positive in 41 % of cases, with HAdV being the most prevalent virus detected (36 %), but no significant correlation was found between the presence of HAdV and human NoV, HAV and HEV. The prevalences of human norovirus genogroup II, HEV and human NoV genogroup I were 16, 3 and 0.7 %, respectively, and HAV was not detected. The estimated number of PCR detectable units varied between 24 and 1.4 × 10(3) g(-1) of digestive tract. Interestingly, there appeared to be a significant association between the type of mussel species (M. galloprovincialis) and the positive result of samples, although a complete overlap between country and species examined required this finding to be confirmed including samples of both species from all possible countries of origin.

Crassostrea gigas oysters as a shrimp farm bioindicator of white spot syndrome virus

This study explored whether Crassostrea gigas oysters can be used as a bioindicator of white spot syndrome virus (WSSV) in shrimp farm water canals. Bioassays showed that C. gigas can accumulate WSSV in their gills and digestive glands but do not become infected, either by exposure to seawater containing WSSV or by cohabitation with infected shrimp. The use of a WSSV nested PCR to screen oysters placed in water canals at the entry of a shrimp farm allowed WSSV to be detected 16 d prior to the disease occurring. The finding that C. gigas can concentrate small amounts of WSSV present in seawater without being harmed makes it an ideal sentinel species at shrimp farms.

Concentration of norovirus during wastewater treatment and its impact on oyster contamination

The concentrations of Escherichia coli, F-specific RNA bacteriophage (FRNA bacteriophage), and norovirus genogroup I (NoV GI) and norovirus genogroup II (NoV GII) in wastewater were monitored weekly over a 1-year period at a wastewater treatment plant (WWTP) providing secondary wastewater treatment. A total of 49 samples of influent wastewater and wastewater that had been treated by primary and secondary wastewater treatment processes (primary and secondary treated wastewater) were analyzed. Using a real-time reverse transcription-quantitative PCR (RT-qPCR), the mean NoV GI and NoV GII concentrations detected in effluent wastewater were 2.53 and 2.63 log(10) virus genome copies 100 ml(-1), respectively. The mean NoV concentrations in wastewater during the winter period (January to March) (n = 12) were 0.82 (NoV GI) and 1.41 (NoV GII) log units greater than the mean concentrations for the rest of the year (n = 37). The mean reductions of NoV GI and GII during treatment were 0.80 and 0.92 log units, respectively, with no significant difference detected in the extent of NoV reductions due to season. No seasonal trend was detected in the concentrations of E. coli or FRNA bacteriophage in wastewater influent and showed mean reductions of 1.49 and 2.13 log units, respectively. Mean concentrations of 3.56 and 3.72 log(10) virus genome copies 100 ml(-1) for NoV GI and GII, respectively, were detected in oysters sampled adjacent to the WWTP discharge. A strong seasonal trend was observed, and the concentrations of NoV GI and GII detected in oysters were correlated with concentrations detected in the wastewater effluent. No seasonal difference was detected in concentrations of E. coli or FRNA bacteriophage detected in oysters.

Comparison of norovirus RNA levels in outbreak-related oysters with background environmental levels

Norovirus is the principal agent of bivalve shellfish-associated gastroenteric illness worldwide. Numerous studies using PCR have demonstrated norovirus contamination in a significant proportion of both oyster and other bivalve shellfish production areas and ready-to-eat products. By comparison, the number of epidemiologically confirmed shellfish-associated outbreaks is relatively low. This suggests that factors other than the simple presence or absence of virus RNA are important contributors to the amount of illness reported. This study compares norovirus RNA levels in oyster samples strongly linked to norovirus or norovirus-type illness with the levels typically found in commercial production areas (non-outbreak-related samples). A statistically significant difference between norovirus levels in the two sets of samples was observed. The geometric mean of the levels in outbreak samples (1,048 copies per g) was almost one order of magnitude higher than for positive non-outbreak-related samples (121 copies per g). Further, while none of the outbreak-related samples contained fewer than 152 copies per g, the majority of positive results for non-outbreak-related samples was below this level. These observations support the concept of a dose-response for norovirus RNA levels in shellfish and could help inform the establishment of threshold criteria for risk management.

Microbiological monitoring of bivalves from the Ria Formosa Lagoon (south coast of Portugal): a 20 years of sanitary survey

The microbiological pollution of coastal waters is a major problem, especially in shellfish areas. This article shows the faecal contamination in bivalves from the Ria Formosa Lagoon (south coast of Portugal) along 20 years (1990-2009). The highest values of Escherichia coli in bivalves were obtained during the 90s, related with the discharge of untreated wastewaters and agricultural runoff. In the 2000s contamination levels decreased, with 83% of the population already served by new or remodelled sewage treatment plants. The highest levels were found in bivalves close to the largest city, where punctual and diffuse contamination sources still exist. Bivalves from the less impacted site showed the lowest contamination, an area with more water renewal. Seasonally, the highest levels were in autumn and winter, due to the runoff of waters from rainfall. These were opposite to those in spring and summer, when the highest temperatures and salinity showed a bactericidal effect.

Phages of Bacteroides (GB-124): a novel tool for viral waterborne disease control?

Current fecal indicator bacteria (FIB) and emerging microbial source tracking (MST) methods may indicate the presence and even the likely source of water contamination, but they are less effective at determining the potential risk to health from human enteric viruses. This paper investigates the presence of human-specific phages (detected using a low-cost MST method) in municipal wastewaters (MW) and assesses whether they may be used effectively to screen for the likely presence of human adenovirus (HAdV) and norovirus (NoV). The findings demonstrated that all samples positive for HAdV and/or NoV also contained phages infecting Bacteroides GB-124 (mean = 4.36 log(10) PFU/100 mL) and that GB-124 phages, HAdV, and NoV were absent from samples of nonhuman origin. HAdV and NoV were detected more frequently in MW samples containing higher levels of phages (e.g., >10(2)) and FIB (e.g., >10(3)). Interestingly, at one sewage treatment works (STW), the levels of GB-124 phages present in treated MW were not significantly lower (p = 0.001) than those in untreated MW. There was a positive correlation (R = 0.42) between the size of STW and the number of GB-124 phages present in the final treated effluent. Therefore, the detection of GB-124 phages by a simple phage-lysis method may have considerable potential as a low-cost surrogate for the detection of certain human pathogenic viruses in MW and receiving waters.

Influence of wastewater treatment process and the population size on human virus profiles in wastewater

Human adenovirus (AdV and AdV species F), enterovirus (EV) and norovirus (NoV) concentrations entering wastewater treatment plants (WWTP) serving different-sized communities, and effectiveness of different treatment processes in reducing concentrations were established. Data was combined to create a characteristic and unique descriptor of the individual viral composition and termed as the sample virus profile. Virus profiles were generally independent of population size and treatment process (moving bed biofilm reactors, activated sludge, waste stabilisation ponds). AdV and EV concentrations in wastewater were more variable in small (<4000) and medium-sized (10,000-64,000) WWTP than in large-sized (>130,000 inhabitants) plants. AdV and EV concentrations were detected in influent of most WWTP (AdV range 1.00-4.08 log(10) infectious units (IU)/L, 3.25-8.62 log(10) genome copies/L; EV range 0.7-3.52 log(10) plaque forming units (PFU)/L; 2.84-6.67 log(10) genome copies/L) with a reduced median concentration in effluent (AdV range 0.70-3.26 log(10) IU/L, 2.97-6.95 log(10) genome copies/L; EV range 0.7-2.15 log(10)PFU/L, 1.54-5.28 log(10) genome copies/L). Highest culturable AdV and EV concentrations in effluent were from a medium-sized WWTP. NoV was sporadic in all WWTP with GI and GII concentrations being similar in influent (range 2.11-4.64 and 2.19-5.46 log(10) genome copies/L) as in effluent (range 2.18-5.06 and 2.88-5.46 log(10) genome copies/L). Effective management of WWTP requires recognition that virus concentration in influent will vary - particularly in small and medium plants. Irrespective of treatment type, culturable viruses and NoV are likely to be present in non-disinfected effluent, with associated human health risks dependent on concentration and receiving water usage.

Assessment of the roles of copepod Apocyclops royi and bivalve mollusk Meretrix lusoria in white spot syndrome virus transmission

Here, we investigate the roles of copepods and bivalve mollusks in the transmission of white spot syndrome virus (WSSV), which is the causative pathogen of an acute, contagious disease that causes severe mortalities in cultured shrimp. Copepods are common components in seawater ponds and are often eaten as live food by shrimp post-larvae. WSSV has been detected in these animals, but it is unknown whether this was due to contamination or infection. Meanwhile, the bivalve mollusk Meretrix lusoria is often used as live food for brooders, and in Taiwan, this hard clam is sometimes co-cultured with shrimp in farming ponds. However, mollusks' ability to accumulate, or allow the replication of, shrimp viruses has not previously been studied. In this study, WSSV, the copepod Apocyclops royi and bivalve mollusk M. lusoria were experimentally challenged with WSSV and then assayed for both the presence of the virus and for viral gene expression. Results showed that the WSSV genome could be detected and that the viral loads were increased in a time-dependent manner after challenge both in A. royi and M. lusoria. Reverse transcriptase PCR monitoring of WSSV gene expression showed that WSSV could replicate in A. royi but not in M. lusoria, which suggested that WSSV, while could infect A. royi, was only accumulated in M. lusoria. A bioassay further showed that the WSSV accumulated in M. lusoria could be transmitted to Litopenaeus vannamei and cause severe infection.

Direct sequencing of hepatitis A virus and norovirus RT-PCR products from environmentally contaminated oyster using M13-tailed primers

Human norovirus (HuNoV) and hepatitis A (HAV) are recognized as leading causes of non-bacterial foodborne associated illnesses in the United States. DNA sequencing is generally considered the standard for accurate viral genotyping in support of epidemiological investigations. Due to the genetic diversity of noroviruses (NoV), degenerate primer sets are often used in conventional reverse transcription (RT) PCR and real-time RT-quantitative PCR (RT-qPCR) for the detection of these viruses and cDNA fragments are generally cloned prior to sequencing. HAV detection methods that are sensitive and specific for real-time RT-qPCR yields small fragments sizes of 89-150bp, which can be difficult to sequence. In order to overcome these obstacles, norovirus and HAV primers were tailed with M13 forward and reverse primers. This modification increases the sequenced product size and allows for direct sequencing of the amplicons utilizing complementary M13 primers. HuNoV and HAV cDNA products from environmentally contaminated oysters were analyzed using this method. Alignments of the sequenced samples revealed ≥95% nucleotide identities. Tailing NoV and HAV primers with M13 sequence increases the cDNA product size, offers an alternative to cloning, and allows for rapid, accurate and direct sequencing of cDNA products produced by conventional or real time RT-qPCR assays.

Scientific Opinion on an update on the present knowledge on the occurrence and control of foodborne viruses

A review of the biology, epidemiology, diagnosis and public health importance of foodborne viruses was performed. Data needs to support a risk assessment were also identified. In addition possible control options and their anticipated impact to prevent or reduce the number of foodborne viral human infections were identified, including the scientific reasons for and against the establishment of food safety criteria and process hygiene criteria for viruses for certain food categories. Food may be contaminated by virus during all stages of the food supply chain, and transmission can occur by consumption of food contaminated during the production process (primary production, or during further processing), or contaminated by infected food handlers. Transmission of zoonotic viruses (e.g. HEV) can also occur by consumption of products of animal origin. Viruses do not multiply in foods, but may persist for extended periods of time as infectious particles in the environment, or in foods. At the EU-level it is unknown how much viral disease can be attributed to foodborne spread. The relative contribution of different sources (shellfish, fresh produce, food handler including asymptomatic shedders, food handling environment) to foodborne illness has not been determined. The Panel recommends focusing controls on preventive measures to avoid viral contamination rather than trying to remove/inactivate these viruses from food. Also, it is recommended to introduce a microbiological criteria for viruses in bivalve molluscs, unless they are labelled "to be cooked before consumption". The criteria could be used by food business operators to validate their control options. Furthermore, it is recommended to refine the regulatory standards and monitoring approaches in order to improve public health protection. Introduction of virus microbiological criteria for classification of bivalve molluscs production areas should be considered. A virus monitoring programme for compliance with these criteria should be risk based according to the findings of a sanitary survey.