Follow-Up of Norovirus Contamination in an Oyster Production Area Linked to Repeated Outbreaks

Abstract

A production area repeatedly implicated in oyster-related gastroenteritis in France was studied for several months over 2 years. Outbreaks and field samples were analyzed by undertaking triplicate extractions, followed by norovirus (NoV) detection using triplicate wells for genomic amplification. This approach allowed us to demonstrate that some variabilities can be observed for samples with a low level of contamination, but most samples analyzed gave reproducible results. At the first outbreak, implicated oysters were collected at the beginning of the contamination event, which was reflected by the higher NoV levels during the first month of the study. During the second year, NoV concentrations in samples implicated in outbreaks and collected from the production area were similar, confirming the failure of the shellfish depuration process. Contamination was detected mainly during winter-spring months, and a high prevalence of NoV GI contamination was observed. A half-life of 18 days was calculated from NoV concentrations detected in oysters during this study, showing a very slow decrease of the contamination in the production area. Preventing the contamination of coastal waters should be a priority.

Occurrence of Bacterial Pathogens and Human Noroviruses in Shellfish-Harvesting Areas and Their Catchments in France

“…After centrifugation at 3,000 g for 5 min, the supernatant was recovered. Nucleic acids (NAs) were extracted using the NucliSens extraction kit (BioMérieux) with increasing the lysis buffer volume ( Le Mennec et al, 2017 ). After checking the extraction efficiency by amplification of MgV, HuNoVs GI and GII were detected as previously described using 5 μl of undiluted and 10-fold dilutions of the NA extract on a Mx3000P qPCR System (Agilent Technologies, France).…”

Improving the efficacy of sewage treatment decreases norovirus contamination in oysters

“…For wastewater samples, the re-suspended PEG pellet was mixed with 2 mL of lysis buffer (bioMérieux, Lyon France) (Sima et al, 2011). For oyster samples, after the proteinase K treatment the entire supernatant (around 3 mL) was mixed with 10 mL of lysis buffer (Le Mennec et al, 2017). Both mixtures were incubated for 10 min at room temperature, and after a brief centrifugation to eliminate solid particles (if needed), 50 or 150 µL of paramagnetic silica was added (depending on the volume of lysis buffer), and further incubated for 10 min at room temperature.…”

Optimization of PMAxx pretreatment to distinguish between human norovirus with intact and altered capsids in shellfish and sewage samples

“…Most shellfish-borne outbreaks caused by HuNoVs have been associated with the consumption of raw or under-cooked shellfish, especially oysters (Iritani et al, 2014;Lunestad et al, 2016), usually harvested from waters affected by the discharge of treated and untreated sewage (Campos and Lees, 2014). In addition, the scientific community agrees on the inadequacy of commercial shellfish depuration processes for HuNoVs (Le Mennec et al, 2017;McLeod et al, 2017) that could be explained by the presence of oyster ligands which specifically bind HuNoVs (Le Guyader et al, 2012).…”