Technical specifications for a European baseline survey of norovirus in oysters

Abstract

The European Commission requested scientific technical assistance in the preparation of a survey protocol for a European Union (EU) coordinated monitoring programme on the prevalence of norovirus (NoV) in raw 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%. The survey protocol defines the target population, the sample size for the survey, sample collection requirements, the analytical method for the quantification of NoV copy number (genotype I and genotype II), the data reporting requirements and the plan of analysis. The sample unit in production areas is a classified production area actively growing commercial oysters (whether harvesting or not is occurring) and for dispatch centres is a quantity of live oysters which are being packed and labelled with an Identification Mark. Based on a multistage sampling scheme, 1,026 samples from 171 production areas and 1,182 samples from 197 dispatch centres should be taken annually in Europe. To reduce the probability of surveying an atypical year, the survey is to be repeated for a second year. The samples are to be analysed according to the method specification developed by the European Union Reference Laboratory (EURL) expert working group, which is compliant with ISO/DIS 15216‐1. Generalised linear models will be used to estimate proportion (with 95% confidence intervals) of sample units with NoV contamination for the following thresholds: < limit of quantification (LOQ), 100, 200, 500, 1,000, 5,000, 10,000 and > 10,000 copies/g. The necessary data to be reported by the sampler and the laboratory to support this analysis is presented in two data models. The results of the survey should be reported using the EFSA data collection framework.

Exploring the Astrovirome of Shellfish Matrices Using Nanopore Sequencing

“…Samples were collected within two sampling campaigns: Oyster ( Crassostrea gigas ) sampling within the “European baseline survey of norovirus in oysters” [ 28 , 29 ] (November 2016–October 2018). Samples were taken every two months from four production areas (one class A and three class B, according to the EU Commission Implementing Regulation 2019/627) located in the northern and southern Adriatic and Thyrrenian sea, respectively (Venetian Lagoon, Apulia, Gulf of La Spezia and Sardinia).…”

Passive Samplers, a Powerful Tool to Detect Viruses and Bacteria in Marine Coastal Areas

“…General Bacteroidales and host-associated bacterial qPCR markers have been developed to identify fecal pollution and to distinguish fecal sources, i.e., human, bovine, porcine, avian, etc., respectively (Layton et al, 2006;Jarde et al, 2018). Among the human enteric viruses shed into the environment, NoV is currently the most frequent human pathogen detected in oysters and the most frequently implicated in gastroenteritis outbreaks linked to oyster consumption in Europe (EFSA, 2016). NoV-contaminated oysters have been detected worldwide following the malfunction of wastewater treatment plants during heavy rainfall or extreme weather events and subsequent contamination of marine waters.…”

Foodborne Norovirus State of Affairs in the EU Rapid Alert System for Food and Feed

“…Of particular relevance are the achievement of at least 90 °C for at least 90 s in the mollusc flesh and the inactivation of viruses [24]. EFSA has also reported on technical specifications of a baseline survey in oysters [25] and some “strong-evidence food-borne outbreaks” caused by viruses in the EU in 2015 [26]. …”