Characterisation of norovirus contamination in an Irish shellfishery using real-time RT-qPCR and sequencing analysis

• Published in: International Journal of Food Microbiology
• Main Authors: Rajko-Nenow, Paulina, Keaveney, Sinéad, Flannery, John, O'Flaherty, Vincent, Doré, William
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2012
• Subjects: Norovirus; Oysters; Seasonality; Multiple genotypes; RT-qPCR; Crassostrea gigas
• Online Access: http://hdl.handle.net/10793/862; https://doi.org/10.1016/j.ijfoodmicro.2012.10.001

Copyright © 2012 Rajko-Nenow et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Peer reviewed Norovirus (NoV) is the single most important agent of foodborne viral gastroenteritis worldwide. Bivalve shellfish, such as oysters, grown in areas contaminated with human faecal waste may become contaminated with human pathogens including NoV. A study was undertaken to investigate NoV contamination in oysters (Crassostrea gigas) from a shellfishery over a 24 month period from October 2007 to September 2009. Oyster samples were collected monthly from a commercial shellfish harvest area classified as category B under EU regulations, but that had had been closed for commercial harvesting due to its previous association with NoV outbreaks. Real-time reverse transcription quantitative PCR (RT-qPCR) was used to determine the concentration of human NoV genogroups I and II (GI and GII) in monthly samples. Total NoV (GI and GII) concentrations in NoV positive oysters ranged from 97 to 20,080 genome copies g− 1 of digestive tissue and displayed a strong seasonal trend with greater concentrations occurring during the winter months. While NoV GII concentrations detected in oysters during both years were similar, NoV GI concentrations were significantly greater in oysters during the winter of 2008/09 than during the winter of 2007/08. To examine the NoV genotypes present in oyster samples, sequence analysis of nested RT-PCR products was undertaken. Although NoV GII.4 is responsible for the vast majority of reports of outbreaks in the community, multiple NoV genotypes were identified in oysters during this study: GI.4, GI.3, GI.2, GII.4, GII.b, GII.2, GII.12, and GII.e. NoV GI.4 was the most frequently detected genotype throughout the study period and was detected in 88.9% of positive samples, this was followed by GII.4 (43.7%) and GII.b (37.5%). This data ...