Jean-Come Piquet

Bioaccumulation efficiency, tissue distribution and environmental occurrence of hepatitis E virus in bivalve shellfish from France

ABSTRACT Hepatitis E virus (HEV), an enteric pathogen of both humans and animals, is excreted by infected individuals and is therefore present in wastewaters and coastal waters. As bivalve molluscan shellfish are known to concentrate viral particles during the process of filter feeding, they may accumulate this virus. The bioaccumulation efficiencies of oysters (Crassostrea gigas), flat oysters (Ostrea edulis), mussels (Mytilus edulis), and clams (Ruditapes philippinarum) were compared at different time points during the year. Tissue distribution analysis showed that most of the viruses were concentrated in the digestive tissues of the four species. Mussels and clams were found to be more sensitive to sporadic contamination events, as demonstrated by rapid bioaccumulation in less than 1 h compared to species of oysters. For oysters, concentrations increased during the 24-h bioaccumulation period. Additionally, to evaluate environmental occurrence of HEV in shellfish, an environmental investigation was undertaken at sites potentially impacted by pigs, wild boars, and human waste. Of the 286 samples collected, none were contaminated with hepatitis E virus, despite evidence that this virus is circulating in some French areas. It is possible that the number of hepatitis E viral particles discharged into the environment is too low to detect or that the virus may have a very short period of persistence in pig manure and human waste.

Impact of xynthia tempest on viral contamination of shellfish.

ABSTRACT Viral contamination in oyster and mussel samples was evaluated after a massive storm with hurricane wind named “Xynthia tempest” destroyed a number of sewage treatment plants in an area harboring many shellfish farms. Although up to 90% of samples were found to be contaminated 2 days after the disaster, detected viral concentrations were low. A 1-month follow-up showed a rapid decrease in the number of positive samples, even for norovirus.

Improving the efficacy of sewage treatment decreases norovirus contamination in oysters

As human population increases worldwide, water quality will become increasingly problematic, and food consumed raw may be of higher risk. This is already evident for oysters grown in coastal areas - despite regulations based on bacterial indicators, oysters are still implicated in food-borne outbreaks worldwide. The pathogens most frequently detected are human noroviruses, which are shed at high concentrations in human excreta and are very resistant to environmental conditions. Sewage treatment plants usually apply a variety of steps such as activated sludge treatment, chlorine or UV disinfection to eliminate contaminants, these processes have variable efficacy. This study demonstrates the impact of replacing an old lagoon-based sewage treatment plant with a new membrane bioreactor sewage treatment plant on human norovirus levels in treated sewage and oysters. While comparable norovirus concentrations were detected in the influent samples, a clear difference was observed in effluent quality, as norovirus was only detected in one sample after treatment in the new membrane bioreactor system, confirming the efficiency of such technology. As a direct impact, oysters located close to the membrane bioreactor sewage outfall were less frequently contaminated by norovirus, and showed lower concentrations compared to the first period of the study when they were exposed to sewage effluent from the lagoon outfall. Shellfish located upstream showed comparable contamination levels suggesting that there are also other sources of norovirus contamination in the estuary. Considering the health benefits of shellfish consumption, improving wastewater quality will make an important contribution to enhancing the safety of shellfish and international food security.

Faecal contamination of echinoderms: first report of heavy Escherichia coli loading of sea urchins from a natural growing area.

Although little evidence existed to support that view, European countries and in particular France, have regarded echinoderms, including sea urchins, as low risk in terms of feacal contamination. It is hypothesized that the sea urchins mode of feeding, which is based on grazing and differs from bivalve molluscs, would prevent it from concentrating high levels of Escherichia coli. Here, we monitored E. coli levels in sea urchins (Paracentrotus lividus) and in filter‐feeder mussels (Mytillus galloprovincialis), collected concurrently from the same natural area over a 1‐year period to verify this assumption. Sea urchins were collected on the seafloor, whereas mussels were collected from the water column at a depth of 4 m. Our results showed heavy bacterial loading of sea urchins in a natural growing environment. Moreover, we highlighted that E. coli contamination of sea urchins could, in certain conditions, be higher than those detected in filter‐feeding mussels collected at the same location. Finally, the results showed a significant correlation between rainfall and E. coli concentrations in sea urchins, suggesting that the bacterial safety of sea urchin could be linked to the quality of the surrounding water.