Management of health risks associated with oysters harvested from a norovirus contaminated area, Ireland, February–March 2010

Copyright © 2010 B. Doré et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Peer reviewed.Oysters from a harvesting area responsible for outbreaks of gastroenteritis were relaid at a clean seawater site and subsequently depurated in tanks of purified seawater at elevated temperatures. This combined treatment reduced norovirus levels to those detected prior to the outbreak. On the basis of norovirus monitoring the sale of treated oysters was permitted although the harvest area remained closed for direct sale of oysters. No reports of illness have been associated with the consumption of treated oysters

Decay rates of faecal indicator bacteria from sewage and ovine faeces in brackish and freshwater microcosms with contrasting suspended particulate matter concentrations

AbstractTo safeguard human health, legislative measures require the monitoring of faecal indicator bacteria (FIB) concentrations in recreational and shellfish waters. Consequently, numerous studies have focussed on FIB survival in the water column and more recently in estuarine sediments. However, there is a paucity of information regarding the influence of contrasting suspended particulate matter (SPM) concentrations on the survival of FIB in the water column of estuaries. Here, microcosms containing freshwater or brackish water with low, high and extreme SPM concentrations were inoculated with sewage and ovine faeces and the decay rate of Escherichia coli, coliforms and enterococci were determined by enumeration over five consecutive days. E. coli derived from ovine faeces proliferated and persisted at high levels in both freshwater and brackish microcosms (no decay), whereas ovine enterococci demonstrated a net decay over the duration of the experiment. Furthermore, SPM concentration had a significant effect on the decay rates of both E. coli and enterococci from ovine faeces in brackish microcosms, but decay rate was greater at low SPM concentrations for E. coli, whereas the opposite was observed for enterococci, whose decay rates increased as SPM concentration increased. E. coli, enterococci and coliforms derived from wastewater demonstrated a net decay in both freshwater and brackish microcosms, with contrasting effects of SPM concentration on decay rate. In addition, some FIB groups demonstrated contrasting responses (decay or proliferation) in the first 24h following inoculation into freshwater versus brackish microcosms. Overall, SPM concentrations influenced the proliferation and decay rates of FIB in brackish waters, but had minimal influence in freshwater. These results demonstrate that the survival rates of FIB in aquatic environments are system specific, species and source dependent, and influenced by SPM concentration. This study has important implications for catchment-based risk assessments and source apportionment of FIB pollution in aquatic environments

The interaction of human microbial pathogens, particulate material and nutrients in estuarine environments and their impacts on recreational and shellfish waters

Anthropogenic activities have increased the load of faecal bacteria, pathogenic viruses and nutrients in rivers, estuaries and coastal areas through point and diffuse sources such as sewage discharges and agricultural runoff. These areas are used by humans for both commercial and recreational activities and are therefore protected by a range of European Directives. If water quality declines in these zones, significant economic losses can occur. Identifying the sources of pollution, however, is notoriously difficult due to the ephemeral nature of discharges, their diffuse source, and uncertainties associated with transport and transformation of the pollutants through the freshwater–marine interface. Further, significant interaction between nutrients, microorganisms and particulates can occur in the water column making prediction of the fate and potential infectivity of human pathogenic organisms difficult to ascertain. This interaction is most prevalent in estuarine environments due to the formation of flocs (suspended sediment) at the marine-freshwater interface. A range of physical, chemical and biological processes can induce the co-flocculation of microorganisms, organic matter and mineral particles resulting in pathogenic organisms becoming potentially protected from a range of biotic (e.g. predation) and abiotic stresses (e.g. UV, salinity). These flocs contain and retain macro- and micro- nutrients allowing the potential survival, growth and transfer of pathogenic organisms to commercially sensitive areas (e.g. beaches, shellfish harvesting waters). The flocs can either be transported directly to the coastal environment or can become deposited in the estuary forming cohesive sediments where pathogens can survive for long periods. Especially in response to storms, these sediments can be subsequently remobilised releasing pulses of potential pathogenic organisms back into the water column leading to contamination of marine waters long after the initial contamination event occurred. Further work, however, is still required to understand and predict the potential human infectivity of pathogenic organisms alongside the better design of early warning systems and surveillance measures for risk assessment purposes

Spatial patterns and environmental constraints on ecosystem services at a catchment scale

Improved understanding and prediction of the fundamental environmental controls on ecosystem service supply across the landscape will help to inform decisions made by policy makers and land-water managers. To evaluate this issue for a local catchment case study, we explored metrics and spatial patterns of service supply for water quality regulation, agriculture production, carbon storage, and biodiversity for the Macronutrient Conwy catchment. Methods included using ecosystem models such as LUCI and JULES, integration of national scale field survey datasets, earth observation products and plant trait databases, to produce finely resolved maps of species richness and primary production. Analyses were done with both 1x1 km gridded and subcatchment data. A common single gradient characterised catchment scale ecosystem services supply with agricultural production and carbon storage at opposing ends of the gradient as reported for a national-scale assessment. Species diversity was positively related to production due to the below national average productivity levels in the Conwy combined with the unimodal relationship between biodiversity and productivity at the national scale. In contrast to the national scale assessment, a strong reduction in water quality as production increased was observed in these low productive systems. Various soil variables were tested for their predictive power of ecosystem service supply. Soil carbon, nitrogen, their ratio and soil pH all had double the power of rainfall and altitude, each explaining around 45% of variation but soil pH is proposed as a potential metric for ecosystem service supply potential as it is a simple and practical metric which can be carried out in the field with crowd-sourcing technologies now available. The study emphasises the importance of considering multiple ecosystem services together due to the complexity of covariation at local and national scales, and the benefits of exploiting a wide range of metrics for each service to enhance data robustness

Simulated sunlight inactivation of norovirus and frna bacteriophage in seawater

Aims: To investigate norovirus (NoV) and F-specific RNA (FRNA) bacteriophage inactivation in seawater under simulated sunlight and temperature conditions representative of summer (235Wm(-2); 17 degrees C) and winter (56Wm(-2); 10 degrees C) conditions in Ireland. Methods and Results: Inactivation experiments were carried out using a collimated beam of simulated sunlight and 100ml of filtered seawater seeded with virus under controlled temperature conditions. NoV concentrations were determined using RT-qPCR, and FRNA bacteriophage concentrations were determined using RT-qPCR and by plaque assay. For all virus types, the fluence required to achieve a 90% reduction in detectable viruses (S-90 value) using RT-qPCR was not significantly different between summer and winter conditions. S-90 values for FRNA bacteriophage determined by plaque assay were significantly less than those determined by RT-qPCR. Unlike S-90 values determined by RT-qPCR, a significant difference existed between summer and winter S-90 values for infectious FRNA bacteriophage. Conclusions: This study demonstrated that RT-qPCR significantly overestimates the survival of infectious virus and is therefore unsuitable for determining the inactivation rates of viruses in seawater. Significance and Impact of the Study: Results from this study provide initial data on the inactivation of NoV and FRNA bacteriophage in seawater under representative summer and winter conditions and will be of interest to shellfish and water management agencies alike

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