J.C. Le Saux

Fecal Contamination in Coastal Areas: An Engineering Approach

Introduction : The occurrence of pathogenic microorganisms in seawater or in shellfish could exist anytime sewage from human or animal origin would be discharged to the coast (Metcalf, 1982). According to the diseases occurring in the human population or in animals, pathogens might be present in recreational waters or in shellfish. Thus, the presence of human enteric viruses (norovirus, astrovirus, rotavirus, hepatitisAvirus (HAV)) and pathogenic bacteria (Salmonella, Listeria monocytogenes, Shiga-toxin-producing Escherichia coli (STEC), Vibrio cholerae, Vibrio parahaemolyticus, etc.) has been reported in coastal areas for a long time (Colwell, 1978; Metcalf, 1978; Melnick et al., 1979; Grimes, 1991; Bosch et al., 2001;Kong et al., 2002). These microorganisms have been implicated in gastrointestinal and respiratory illnesses and other infections (skin, eyes, etc.), (Griffin et al., 2003). Using risk-assessment models for viruses, maximum risks were estimated to be 1.3 infections per 100 swimmers (Colwell et al., 1996). To evaluate the risk due to the presence of these pathogens in the environment, certain criteria have to be determined. Among them, the infectious dosewould be of a greatest importance (Table 14.1). Even if the infectious dose vary with the strains, the age of the patient, or other parameters, some pathogens are highly dangerous for men even at low concentrations (HAV, E. coli O157:H7, V. cholerae), whereas others have to be ingested in high concentrations to be harmful (V. parahaemolyticus) or are highly infectious but not very dangerous (norovirus). Thus, for some pathogens, a low contamination in seafood, for example, is not acceptable, based on risk-assessment models (Colwell et al., 1996). Among bacteria, the Vibrio family plays an important role in infections, waterborne or seafood diseases, especially in countries surrounded by warm marine waters. Toxigenic V...

A norovirus oyster-related outbreak in a nursing home in France, January 2012

The presence of norovirus in shellfish is a public health concern in Europe. Here, we report the results of an investigation into a norovirus gastroenteritis outbreak following a festive lunch which affected 84 (57%) residents and staff members of a nursing home in January 2012 in France. Individuals who had eaten oysters had a significantly higher risk of developing symptoms in the following 2·5 days than those who had not, the risk increasing with the amount eaten [relative risk 2·2 (1·0-4·6) and 3·3 (1·6-6·6) for 3-4 and 5-12 oysters, respectively]. In healthy individuals during those days, 29 (32%) subsequently became ill, most of whom were staff members performing activities in close contact with residents. Genogroup II noroviruses were detected in faecal samples, in a sample of uneaten oysters and in oysters from the production area. Identifying a noroviruss infectious dose may facilitate the health-related management of contaminated shellfish.

Modeling and evaluation of compliance to water quality regulations in bathing areas on the Daoulas catchment and estuary (France)

The microbiological quality of waters in estuaries determines their acceptability for recreational uses. Microbiological contamination often results from urban wastewater discharges or non-point source pollution (manure spreading), and can cause bathing zones to be closed. European regulations (EC/7/2006) have proposed standards (500 E. coli/100 ml) for the acceptability areas for bathing. In this study, two models were associated to simulate contamination: SWAT on a catchment and MARS 2D in the downstream estuary. After river flow calibration and validation, two scenarios were simulated in SWAT, and E. coli fluxes obtained at the main outlet of the catchment were then introduced into MARS 2D to follow E. coli concentrations in the estuary. An annual evaluation of compliance to bathing area water quality standards was then calculated, linked with daily rainfall classes. Water quality in the estuary was below the standard on 13 days, including 5 days with rainfall superior to 10 mm, due to faecal contamination from soil leaching by rain, and 5 days with rainfall ranging from 0.1 to 5 mm/day, due to the high frequency of this level of rainfall. To conclude, this study allowed us to demonstrate the efficiency of models to gain a better understanding on water quality degradation factors.

Quantitative approach of risk management strategies for hepatitis a virus-contaminated oyster production areas.

It is not yet known whether using the new molecular tools to monitor hepatitis A virus (HAV) in shellfish production areas could be useful for improving food safety. HAV contamination can be acute in coastal areas, such as Brittany, France, where outbreaks of hepatitis A have already occurred and have been linked to the consumption of raw shellfish. A quantitative probabilistic approach was carried out to estimate the mean annual risk of hepatitis A in an adult population of raw oyster consumers. Two hypothetical scenarios of contamination were considered, the first for a rare and brief event and the second for regular and prolonged episodes of contamination. Fourteen monitoring and management strategies were simulated. Their effects were assessed by the relative risk reduction in mean annual risk. The duration of closure after abnormal detection in the shellfish area was also considered. Among the strategies tested, results show that monthly molecular reverse transcription PCR monitoring of HAV is more useful than bacterial surveys. In terms of management measures, early closure of the shellfish area without waiting for confirmatory analysis was shown to be the most efficient strategy. When contamination is very short-lived and homogeneous in the shellfish production area, waiting for three negative results before reopening the area for harvest is time wasting. When contamination is not well identified or if contamination is heterogeneous, it can be harmful not to wait for three negative results. In addition, any preventive measures, such as improving sewage treatment or producing shellfish in safer areas, that can reduce contamination by at least 2 log units are more efficient and less costly. Finally we show that controlling and managing transferred shellfish are useful and can play an important role in preventing cases. Qualitative results from HAV monitoring can advantageously supplement other measures that improve the safety of shellfish products in exposed areas.

Monitoring viral contamination of molluscan shellfish.

Abstract: This chapter focuses on the enteric viruses, hepatitis A virus and norovirus, responsible for the main outbreaks linked to shellfish consumption. One major drawback for viral contamination estimation in shellfish is the lack of indicator or standardised method, preventing systematic control. After a review of the main sources of pollution, we identified the conditions responsible for shellfish contamination. This will help to set up potential strategies to reduce contamination in harvesting areas such as the limitation of faecal input or the improvement of tools for management. As knowledge is progressing risk management, strategies will help to protect the consumer and will also led to improve regulation. Rapid alert systems need to be set up to prevent coastal area contamination and promising examples of coastal management have proved their efficacy to reduce faecal load and thus, improve water quality. Shellfish have long been recognised as being beneficial to human health and this benefit should also be taken into consideration in managing coastal areas and preserving the water quality.