Risk assessment: The risk to vulnerable consumers from Listeria monocytogenes in ready-to-eat smoked fish

Summary

Infection with the bacteria Listeria monocytogenes can cause serious illness in people who are more vulnerable to infection, and hospitalisation and death can occur in serious cases. There are several factors that make people more vulnerable to infection with this bacteria, such as:

• pregnancy (where infection may lead to miscarriage or illness in newly born babies)
• ageing (as the immune system weakens with age, older adults - usually defined as those who are aged 65 and over - can be more susceptible to listeriosis compared with the general population)
• people who are considered immunocompromised due to a medical condition or treatment

Certain ready-to-eat foods (foods that are not expected to undergo cooking) can allow the survival and growth of Listeria monocytogenes. Ready-to-eat smoked fish (such as smoked salmon and trout) is recognised as one of these foods.

This risk assessment was requested to provide evidence to support a review of the advice for vulnerable consumers on the risk of eating ready-to-eat smoked fish.

This risk assessment was compiled by a team of Risk Assessors from Food Standards Scotland and the Food Standards Agency following the internationally recognised framework for risk assessment. The evidence we gathered and reviewed came from academic publications, as well as national and international reports and surveys. We also looked at incidents involving Listeria monocytogenes and illness in consumers.

To come to our final risk conclusion we considered the hazard of Listeria monocytogenes including factors that allow contamination, survival and growth in food, and the ability to cause disease in humans (known as listeriosis). We looked at outbreaks of disease associated with smoked fish, and the detection of Listeria monocytogenes in smoked fish intended for sale. Finally, we also considered the production of smoked fish, and routes of contamination, or control steps that may limit the presence of the pathogen in the final product.

To ensure quality, our draft risk assessment was reviewed by senior staff internally, and externally by the Incidents Subgroup of the Scientific Advisory Committee for Microbiological Safety of Food.

Read about the Scientific Advisory Committee for Microbiological Safety of Food.

Conclusion of the risk assessment

The risk conclusion was given using an internationally recognised scoring system where likelihood is scored between negligible and very high, and severity is scored between negligible and high.

The frequency/likelihood of occurrence of invasive listeriosis in the vulnerable population from consumption of cold smoked fish is low. This is defined as rare but does occur.

The frequency/likelihood of occurrence of invasive listeriosis in the vulnerable population from consumption of hot smoked fish is very low. This is defined as very rare but cannot be excluded.

The severity of illness from listeriosis in the vulnerable population is high. This is defined as severe illness causing life-threatening or substantial sequelae or illness of long duration.

As part of the risk assessment process we also highlighted any uncertainties, for example the lack of data on the dose of Listeria monocytogenes required to make a vulnerable consumer unwell.

Read our latest guidance on what listeria is and how to reduce your risk of infection.