Shellfish Microbiology

ShellfishBivalve filter-feeding molluscan shellfish can accumulate human pathogenic bacteria and viruses when grown in sewage contaminated waters. Such shellfish represent a public health risk when consumed raw or only lightly cooked. Control measures are in place to prevent the occurrence of illness. These measures are based around the use of bacterial (E. coli) standards. Shellfish production areas in Ireland are classified on the basis of criteria as outlined in the European Union Hygiene Regulations (EU hygiene regulations).

Despite these controls, however, outbreaks of viral illness associated with the consumption of shellfish continue to occur throughout the world. Principal among the agents related to such outbreaks are Norovirus (NoV) and Hepatitis A virus (HAV). Gastroentieritis caused by NoV is the most frequently occurring problem in Europe.

The Marine Institute is the National Reference Laboratory (NRL) in Ireland for monitoring the bacteriological and viral contamination of bivalve shellfish. The NRL works closely with the competent authorities and the shellfish industry to ensure that Irish shellfish are produced to the highest microbial standards. The competent authorities in Ireland are the Sea-Fisheries Protection Authority and the Food Safety Authority of Ireland. The NRL advises the competent authorities on the classification of shellfish production areas.

The duties of the NRL are:

  • Coordinating the activities of national laboratories responsible for viral and bacteriological analyses of bivalve molluscs.
  • Assisting the competent authority to organise a system for monitoring viral and bacteriological contamination of bivalve molluscs.
  • Disseminating the information provided by the Community Reference Laboratory (CRL) for monitoring the bacteriological and viral contamination of bivalve shellfish to the competent authorities and national laboratories.

The Irish NRL works closely with the CRL, which is based at the Centre for Environment and Aquaculture Services (CEFAS) in the UK.

In summary the services provided by the NRL are:

  • Coordinating the activities of national testing laboratories (Mirobiological monitoring program)
  • Assistance to the Competent Authority with classification of shellfish harvesting areas
  • Norovirus and hepatitis A virus analysis
  • E. coli, Salmonella spp and FRNA Bacteriophage analysis


Further information on the National Reference Laboratory at the Marine Institute can be obtained from Bill Dore.