Strategies to reduce norovirus (NoV) contamination from oysters under depuration conditions

Younger, Andrew; Neish, Anna; Walker, Duard L.; Jenkins, Kaitlyn L.; Lowther, James; Stapleton, Tina

doi:10.1016/j.fct.2020.111509

Cited by 12 publications

(11 citation statements)

References 22 publications

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“…Parameters of seawater, such as temperature, salinity, dissolve oxygen content, turbidity, and phytoplankton concentration, can affect shellfish filtration efficiency, playing a relevant role in the effectiveness of depuration processes [ 12 , 13 , 14 , 15 ]. Some studies suggest that, in the same condition, the effectiveness of depuration in mollusks might differ between bivalve species and virus types/strains [ 10 , 16 , 17 , 18 , 19 , 20 ]. Specific NoV ligands found in oyster tissues, for example, may contribute to the persistence of viral particles and resistance to depuration [ 10 , 21 , 22 , 23 ].…”

Section: Introductionmentioning

confidence: 99%

“…Most of the studies regarding the purification rate of noroviruses from oysters have been done with artificially contaminated oysters [ 11 , 13 , 19 , 25 , 26 ]. As far as we know, only two research studies have evaluated the effectiveness of depuration process in the reduction of NoV in naturally contaminated oysters (species Crassostrea gigas ) subjected to purification for 5 [ 18 ] and 7 days [ 27 ]. Therefore, in our investigation, we chose to indagate NoV reduction in naturally contaminated oysters subjected to purification processes of different lengths (1, 4, and 9 days postharvest) in a commercially authorized plant.…”

Section: Introductionmentioning

confidence: 99%

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Norovirus Persistence in Oysters to Prolonged Commercial Purification

et al. 2021

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Depuration is generally the main treatment employed for bivalve mollusks harvested from contaminated sites. Commercial depuration has demonstrated to be effective for removal of bacterial pathogens, although it probably provides only limited efficacy against human enteric viruses. We evaluated the quantitative reduction of norovirus (NoV) genogroups I and II in naturally contaminated oysters after 1, 4, and 9 days of depuration. The process was conducted in an authorized depuration plant, and NoV concentration was determined by RT-qPCR according to ISO 15216-1:2017 method. Regardless of the NoV genogroup, our results showed no significant reduction in NoV concentration after 1 day of depuration. Higher mean reduction (68%) was obtained after 4 days of treatment, while no further increase was observed after 9 days. Overall, reduction was highly variable, and none of the trials showed statistically significant reduction in NoV RNA concentration at the end of each depuration period. Indeed, NoV concentration remained high in 70% of samples even after 9 days of depuration, with values ranging between 4.0 × 102 and 2.3 × 104 g.c./g. These results indicate that an extension of commercial depuration time does not appear to be effective for reducing or eliminating NoV in oysters.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Norovirus Persistence in Oysters to Prolonged Commercial Purification

et al. 2021

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“…In contrast, all oysters in the tested population were found to be contaminated when the mean concentration tested above 300 gcg −1 (Hunt 2019 ). Additionally, two recent studies investigated the FRNA bacteriophage type II (norovirus surrogate) removal from oysters during depuration using genomic and infectivity methods (Leduc et al 2020 ; Younger et al 2020 ). These studies indicated that viruses may either be inactivated in oysters during depuration (Leduc et al 2020 ) or, as suggested by Younger et al ( 2020 ), destroyed and removed.…”

Section: Discussionmentioning

confidence: 99%

“…Additionally, two recent studies investigated the FRNA bacteriophage type II (norovirus surrogate) removal from oysters during depuration using genomic and infectivity methods (Leduc et al 2020 ; Younger et al 2020 ). These studies indicated that viruses may either be inactivated in oysters during depuration (Leduc et al 2020 ) or, as suggested by Younger et al ( 2020 ), destroyed and removed. Despite the differences in the concluded viral reduction mechanisms these findings could indicate that the virus genome copies detected using RT-PCR methods are, at least in part, only footprints left by the infectious virus particles and they no longer have the capability of causing infection especially at low concentrations (i.e.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of Norovirus Reduction in Environmentally Contaminated Pacific Oysters During Laboratory Controlled and Commercial Depuration

et al. 2021

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Norovirus contamination of oysters is the lead cause of non-bacterial gastroenteritis and a significant food safety concern for the oyster industry. Here, norovirus reduction from Pacific oysters (Crassostrea gigas), contaminated in the marine environment, was studied in laboratory depuration trials and in two commercial settings. Norovirus concentrations were measured in oyster digestive tissue before, during and post-depuration using the ISO 15216-1 quantitative real-time RT-PCR method. Results of the laboratory-based studies demonstrate that statistically significant reductions of up to 74% of the initial norovirus GII concentration was achieved after 3 days at 17–21 °C and after 4 days at 11–15 °C, compared to 44% reduction at 7–9 °C. In many trials norovirus GII concentrations were reduced to levels below 100 genome copies per gram (gcg−1; limit of quantitation; LOQ). Virus reduction was also assessed in commercial depuration systems, routinely used by two Irish oyster producers. Up to 68% reduction was recorded for norovirus GI and up to 90% for norovirus GII reducing the geometric mean virus concentration close to or below the LOQ. In both commercial settings there was a significant difference between the levels of reduction of norovirus GI compared to GII (p < 0.05). Additionally, the ability to reduce the norovirus concentration in oysters to < LOQ differed when contaminated with concentrations below and above 1000 gcg−1. These results indicate that depuration, carried out at elevated (> 11 °C) water temperatures for at least 3 days, can reduce the concentration of norovirus in oysters and therefore consumer exposure providing a practical risk management tool for the shellfish industry.

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“…Bivalve aquaculture is actually a feasible and sustainable form with no artificial diets (Mao et al, 2006). Nevertheless, many factors have limited the sustainable development of bivalve aquaculture, including water pollution (Chen et al, 2020; Han et al, 2020; Li et al, 2020), diseases (Le et al, 2020; Younger et al, 2020), genetic bottlenecks, uncertain meat quality (Willer & Aldridge, 2019), expensive microalgae diets and primary limiting factors. Microalgae cultivation is not only difficult, but also very expensive and susceptible to contamination, which accounts for 30%–50% of the total hatchery expenditures (Gui et al, 2016; Nevejan et al, 2007), so it is an economic problem that cannot be ignored by the shellfish industry.…”

Section: Introductionmentioning

confidence: 99%

Evaluation on feasibility of two probiotics as microalgae substitutes for Ruditapes philippinarum spat cultured in shrimp aquaculture wastewater

Liu

Zhang

et al. 2021

Aquaculture Research

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Microalgae, a kind of conventional bait for bivalves, can increase the cost of shellfish aquaculture. On this basis, Ruditapes philippinarum spat was selected to evaluate the feasibility of using photosynthetic bacteria (PSB) and marine yeasts as microalgae substitutes. The results showed that the addition of bacteria obviously affected the growth status of spat. Firstly, the survival rate of spat in 5%, 40%, 50% and 70% PSB substitution groups as well as 5% and 40% yeast substitution groups was not significantly different from that in microalgae group (p > 0.05), but that in other substitution groups was significantly lower than that in microalgae group (p < 0.05). Secondly, the growth rate of spat in PSB substitution groups (except for the 10% PSB substitution group) was significantly higher than that in microalgae group, and the 5% PSB substitution group had a growth rate which was 109.55% higher than that in microalgae group. There was no significant difference in the growth rate between microalgae group and 10%, 40%, 50% and 70% yeast substitution groups. Thirdly, the addition of bacteria also affected the digestive ability of shellfish. Pepsin enzyme activity in 20% PSB substitution group was 29.85% higher than that in microalgae group. Moreover, 5% and 40% yeast substitution groups had no significant difference in the pepsin enzyme activity compared with microalgae group. Finally, the nitrogen (N) and phosphorus (P) concentrations in the bacteria addition treatments were higher than those in the control treatment at the end of the experiment, but they were generally maintained at lower levels. In conclusion, it is feasible to partially replace microalgae with PSB and marine yeasts, and it is suggested that shellfish culture should be combined with wastewater utilization to promote the healthy development of aquaculture industry.

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Strategies to reduce norovirus (NoV) contamination from oysters under depuration conditions

Cited by 12 publications

References 22 publications

Norovirus Persistence in Oysters to Prolonged Commercial Purification

Norovirus Persistence in Oysters to Prolonged Commercial Purification

Evaluation of Norovirus Reduction in Environmentally Contaminated Pacific Oysters During Laboratory Controlled and Commercial Depuration

Evaluation on feasibility of two probiotics as microalgae substitutes for Ruditapes philippinarum spat cultured in shrimp aquaculture wastewater

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