Spatial and Temporal Pattern of Norovirus Dispersal in an Oyster Growing Region in the Northeast Pacific

Abstract

Contamination of Pacific oysters, Crassostrea gigas, by human norovirus (HuNoV) is a major constraint to sustainable shellfish farming in coastal waters of the Northeast Pacific. HuNoV is not a marine virus and must originate from a human source. A barrier to effective management is a paucity of data regarding HuNoV dispersal in the marine environment. The main objective of this study was to identify the spatial distribution and persistence of HuNoV in an active shellfish farming region in the Northeast Pacific. Market-size C. gigas were sequentially deployed for two-week intervals at 12 sites during the 2020 winter risk period from January to April. Detection of HuNoV quantification was performed by reverse transcription real-time PCR (RTqPCR) according to method ISO 15216-1:2017, with modifications. RTqPCR did not detect GI HuNoV. The estimated prevalence of GII HuNoV in oyster digestive tissue was 0.8 ± 0.2%. Spatiotemporal analysis revealed that contamination of oysters with GII HuNoV changed through time and space during the surveillance period. A single cluster of oysters contaminated with GII.2 HuNoV was detected in a small craft harbor on 23 April. There was no significant increase in the proportion of positive pools in the next nearest sampling station, indicating that HuNoV is likely to disperse less than 7 km from this non-point source of contamination. Results from this study indicate that HuNoV contamination of coastal waters from non-point sources, such as small craft harbors and urban settings, can pose a significant localised risk to shellfish farming operations in the region.

Study of Shellfish Growing Area During Normal Harvesting Periods and Following Wastewater Overflows in an Urban Estuary With Complex Hydrography

“…Several studies in NZ and overseas have assessed the spatial and temporal distribution of norovirus in coastal environments (Brake et al, 2017 ; Campos et al, 2015 ; Green et al, 2022 ; Greening & Lewis, 2007 ; Winterbourn et al, 2016 ). Overall, these studies show that viral levels decline with distance and time from sewage sources.…”

A Comparison of Two Methods for Detection of Norovirus RNA in Environmental Swab Samples

“…For norovirus, the ISO standard (ISO 15216-1:2017) [12,13] adopted in this study provided a useful reference for evaluation of an alternative method, which was found not to differ significantly in sensitivity. Methods with standardised approaches and defined quantitative controls have recently been used in quantitating the recovery of norovirus from food, which is important in understanding the role of food and food handlers in norovirus transmission pathways [21][22][23].…”

Spatial Distribution and Enrichment Dynamics of Foodborne Norovirus in Oyster Tissues

“…Chassaing et al conducted a meta-analysis of publications on NoV-related foodborne outbreaks from 1993 to 2019 and found that bivalve molluscan shellfish accounted for 53% of the implicated food sources [ 12 ]. For perspective, the prevalence of NoV in oysters from other regions is reported in the range of <2% in Australia, 9% in France, 3.9 to 20% in the USA, 16.9% in China, 32.1% in Spain, and up to 71.6% in the United Kingdom [ 13 ]. Our previous research entailed a year-long investigation into oyster contamination in aquaculture farms and revealed that 16.9% (60/356) of the collected oyster samples tested positive for NoV [ 14 ].…”