Research call: effectiveness of depuration in removing norovirus from oysters

Last updated:
24 March 2014
The Food Standards Agency is inviting tenders to design and execute a research study to identify and evaluate possible enhancements to improve norovirus removal from live oysters during shellfish depuration processes.

About the project

The FSA wants to commission work to quantify and optimise the effectiveness of standard UK depuration practices in reducing norovirus in oysters and to explore the potential for novel approaches to significantly improve the effectiveness of this process. The foodborne viruses’ research programme aims to gather data to provide a robust science and evidence base to inform development of a risk management programme on foodborne viruses, with a particular focus on norovirus.

The study should include reviews of relevant available evidence (published and unpublished) as the starting point for a fully justified laboratory-based project which will improve the controls that can be applied to current UK depuration practices, to reduce the levels of norovirus in oysters sold for public consumption.

How to apply

Applications should be submitted online, using our electronic procurement system (ePPS), by 5pm on Thursday 8 May, 2014.

To find out more about this call for tenders, you will need to register as a supplier on the FSA’s electronic tendering system, ePPS, via the link on this page.

About shellfish contamination and depuration

Shellfish production areas can become contaminated with faecal material from sewage effluent discharges and surface water run-off from agricultural land. This may contaminate oysters and other shellfish with bacteria and viruses known to cause human illness. Oysters filter large volumes of water to get their food and any pathogens in the water can build up within the oyster.

Controls before and after commercial harvesting of oysters, such as relaying and depuration (more about these processes can be found below), provide good protection against harmful bacteria, but are less effective at removing viruses from live shellfish.

Although norovirus contamination can be an issue for a range of foods, the presence of norovirus in oysters can present a particular risk to consumer safety as oysters are generally consumed as a raw product, so the virus is not destroyed before consumption by heat processes such as cooking.


A purification process used to treat bivalve shellfish, but is not commonly used in the UK. Shellfish are harvested from a contaminated area and moved to clean areas, where they are placed on the ocean floor or into containers laid on the ocean floor, or suspended in racks, generally for a period of at least two months.


A purification process used commercially and regulated by the FSA. It is commonly used by producers to reduce or eliminate microbiological contamination in oysters and other shellfish. Shellfish are placed in tanks of clean re-circulating seawater, treated by UV irradiation, and allowed to purge their contaminants over several days. In the UK a minimum purification time of 42 hours is currently required.