NoVs can be classified into different genotypes. Recent studies show that certain strains can bind to the digestive tract of the oyster, resulting in reduced depuration efficacy. Results of the current study provide evidence that elevated temperatures during depuration can achieve significant removal of NoV. However, the extent of removal appears to depend on the strains of NoV present. A raised temperature of 18°C was found to be most effective. Double the rate of NoV GII removal was achieved at 18 °C compared with 8 °C after five days. No difference was found in shelf life between oysters from trials ran at 8 and 18°C than for oysters held at <8°C for up to 12 days post-depuration. The trials also showed improved NoV removal at 25 ppt salinity compared with 35 ppt. This highlighted the importance of depurating oysters in water of a similar salinity (within 20%) to the harvesting area from which they originated. The oysters used in our study came from an estuarine source with salinity typically in the range of 25-30ppt. Feeding and light regimes, water flow and physical disturbance appear not to have any impact on NoV reduction/removal.
Addressing target audiences and expressing needs
- To raise awareness and possibly influence policy
We want to share our results with those working in the shellfish industry and to make regulatory officers (food safety and environmental) monitors aware of our results. We would like shellfish industry members operating depuration systems and the associated regulatory officers to be aware of and to be able to use our new method, reducing produce losses due to contamination and further reducing risks to human health.
- International Organisations (ex. OECD, FAO, UN, etc.)
- Other Actors who can help us fulfil our market potential
R&D, Technology and Innovation aspects
For final commercial implementation, the methodology must be demonstrated in a wider range of commercial depuration systems and with other bivalve species (TRL6), especially in those with higher levels of NoV, as trial concentrations were low in some of the trials. The suitability of FRNA bacteriophage as a surrogate for NoV infectivity under depuration conditions should also be investigated.
