NOROVIRUS and BIVALVE MOLLUSCS

The five recent RASFF (Rapid Alert System for Food and Feed) Foodborne Virus alerts in 2017 are a good reminder of the risks caused by norovirus in bivalve molluscs.

 

Prevalence of Foodborne Viruses in Mussels

In Southern Italy, during a two-year collecting period (2014-2015), more than 50% of the samples collected were positive to at least one foodborne virus. Norovirus represented more than 37% of the detected viruses, followed by Astrovirus, Sapovirus, Hepatitis A Virus... This study described, for the first time, the presence of aichivirus and sapovirus in mussels in Italy.

 

Investigation on Norovirus and HAV Presence

From January 2013 to July 2015, more than 250 samples of bivalve molluscs collected in harvesting areas from a large coastal tract of Southern Italy were screened for HAV and NoV of genogroups GI and GII. Noroviruses' RNA were identified in 14.2% of the samples with a higher prevalence for genogroup GII than genogroup GI. Matching between the NoV genotypes circulating in local population and detected in molluscs confirms the diffusion in the environment of noroviruses.

EFSA and Norovirus

Technical specifications for a European baseline survey of norovirus in oysters : The objective of the survey is to estimate the European prevalence of norovirus-contaminated oysters at production areas and batches of oysters at dispatch centres, with a 95% level of confidence and a level of precision of 5% considering an expected prevalence of 50%.

 

Why Norovirus like so much bivalves

Freshwater and Norovirus

Contaminated water can lead to human health issues; the aims of this work were to determine the presence and identity of representative human pathogenic enteric viruses in water samples from six European countries. A 2-year survey showed that Norovirus ... and Adenoviruses were the most frequently identified enteric viruses in the sampled surface waters. The detectable presence of pathogenic viruses may represent a potential risk for human health.

Shellfish Soup and Norovirus

The aim of this study was to describe a norovirus outbreak connected to insufficient heat treatment during preparation of a shellfish soup in serving portions, during a company Christmas celebration in Norway. Consumers who want to avoid eating raw shellfish, should not assume that the shellfish tissue in preparation as described in our study is adequately heat treated.

Detection Methods for Foodborne Viruses in Bivalves

ISO/TS 15216-1:2013

describes a method for quantification of levels of HAV (Hepatitis A Virus) and NoV (Norovirus) genogroup I (GI) and II (GII) RNA, from test samples of foodstuffs or food surfaces. Following liberation of viruses from the test sample, viral RNA is then extracted by lysis with guanidine thiocyanate and adsorption on silica. Target sequences within the viral RNA are amplified and detected by real-time RT-PCR.

This approach is also relevant for detection of the target viruses on fomites, or of other human viruses in foodstuffs, on food surfaces or on fomites following appropriate validation and using target-specific primer and probe sets

ISO/TS 15216-2:2013

describes a method for qualitative detection of HAV (Hepatitis A Virus) and NoV (Norovirus) genogroups I (GI) and II (GII), from test samples of foodstuffs or food surfaces. Following liberation of viruses from the test sample, viral RNA is then extracted by lysis with guanidine thiocyanate and adsorption on silica. Target sequences within the viral RNA are amplified and detected by real-time RT-PCR.

This approach is also relevant for detection of the target viruses on fomites, or of other human viruses in foodstuffs, on food surfaces or on fomites following appropriate validation and using target-specific primer and probe sets

 

Sources :

• FAO :http://www.fao.org
• RASFF : https://webgate.ec.europa.eu
• ECDC: http://ecdc.europa.eu/en/Pages/home.aspx
• ISO : www.iso.org
• NCBI : www.ncbi.nlm.nih.gov
• bioMérieux : http://www.biomerieux-industry.com/