Research programme B16

Details of the Agency-funded shellfish hygiene research programme.

Aims

The overall aim of this programme is to develop and validate alternative methods for the isolation, detection and confirmation of viral pathogens and marine biotoxins in shellfish. These methods should be robust and suitable for use in surveillance programmes. Also this programme aims to find alternatives to E. coli and faecal coliform bacterial indicators more representative of the viral load.

This research will assist the Agency in obtaining the best available scientific evidence and in meeting its target of reducing the incidence of foodborne disease by 20% by April 2006. Also it will assist the development and implementation of the Agency's fish, shellfish hygiene and European policy.

Abstract

When grown in sewage-polluted water, bivalve molluscan shellfish can accumulate environmental contaminants, including human pathogenic bacteria and viruses, and marine biotoxins produced by some naturally occurring planktonic algae. Hence when consumed raw or lightly cooked shellfish can present a significant health risk. Specific and targeted control measures for reducing risks to human health are required.

To reduce disease hazards from contaminated shellfish, commercial heat treatment and self-purification processes (depuration) are used conventionally. Heat treatment is fully effective provided it is conducted properly. However while depuration appears to remove bacteria from shellfish, it does not remove human viruses rapidly, resulting in frequent outbreaks of viral gastroenteritis in most parts of the world.

The shellfish hygiene programme focuses on two distinct areas of research, the first dealing with viruses, the second with biotoxins.

Viruses
The current statutory monitoring programme is based on E. coli and faecal coliform bacterial indicators, although most diseases associated with shellfish are caused by viral pathogens. Generally, viruses are more persistent than bacteria in marine environments, and an important component of the programme is the development of more robust techniques for the detection of viral pathogens in shellfish. In addition, consumer safety is not guaranteed by obtaining the E. coli standard in depurated shellfish as it is not an accurate measure of viral load. The Agency's work will concentrate on identifying more appropriate viral indicators. Research on the survival and removal of viruses in sewage treatment processes and marine environments, as well trying to enhance the efficacy of commercial depuration processes, will provide much needed guidance for industry.

Biotoxins
The current shellfish surveillance programme for marine biotoxins contains the requirement for statutory tests using live animals (bioassays), which is a sensitive issue. Consequently there is a policy need to find alternative non-animal screening techniques. Faster, more specific detection methods and preferably confirmatory procedures will be developed and validated. This research has the potential to reduce, if not replace, the need for animals in biotoxin monitoring. Information will be made available to the shellfish industry and the European Commission. Also, to better predict the likelihood of pollution incidents, studies will investigate the correlation between algal presence in water and toxin presence in shellfish.

Outputs from this research programme will provide the Agency with real-time, reliable information to support policy objectives of ensuring the safety of the nation's food supply.

Rationale

The ACMSF report on foodborne viral infections (1998) commented and made recommendations for the prevention and control of viral contamination in shellfish. Outbreaks of viral gastroenteritis linked to the consumption of shellfish are still commonplace although Community legislation does not contain microbiological criteria or limits for viruses. Most human pathogenic viruses associated with shellfish cannot be cultured easily, current detection methods are not quantitative, and viability cannot be assessed easily. Bacterial indicators of sewage pollution (section 5) do not always correlate well with the presence of viruses. Current depuration practices stipulate end-product standards for bacteria, which are met during the clean-up process, although little data is present on the depuration of viruses. For the safety of public health, it is not useful to continue using bacterial indicators when the main risk is viral. CEFAS, Weymouth, is the Community Reference Laboratory (CRL) for viruses and all work outlined in this research programme addresses these main issues and complements other work completed in Member states. Through the co-ordination of the CRL the work will focus on defining virological criteria and limits in shellfish and improving depuration procedures, which will ultimately benefit the consumer. This work is linked directly to the Agency's strategy to reduce foodborne disease by 20% by April 2006.

Marine biotoxins are a different, but by no means less important, issue affecting the safety of shellfish harvested in UK waters. Not all algal blooms are toxic but they are commonplace and a natural phenomenon so human intervention has little or no effect on their presence. Some toxins accumulated by shellfish are particularly poisonous and can cause serious illness in humans. The Agency co-ordinates the biotoxin surveillance programme for England and Wales (FSA-Scotland and FSA-Northern Ireland have instigated their own testing programmes). Community legislation has stipulated the use of biological methods (bioassays) for detecting most, but not all, biotoxins in shellfish but have added the provision to use alternative chemical methods if appropriate scientific evidence is available. Current animal tests are not rapid or robust, and specialist knowledge is required for their completion. The shellfish industry is not required to undertake end-product biotoxin testing and the Home Office would be unwilling to sanction increased animal testing required to meet the demands of processors. Future Community legislation is likely to put the emphasis of testing on the food business operators, as well as the official controls carried out by the Competent Authority. Therefore work outlined in this research programme will complement policy decisions that will come into force in the near future.

The importance of this work for improving public safety, policy needs and the requirement for statutory responsibilities can be seen clearly as the main drivers for this research programme.

Contact for further information

Name: 
Dr Kevin Hargin
Tel: 
020 7276 8953