ACMSF draft report on the increased incidence of listeriosis in the UK (Northern Ireland)

The ACMSF provides the FSA with independent expert advice. This helps the Agency ensure that policy development and consumer advice in relation to the microbiological safety of food are based upon sound science and relevant practical experience and expertise. The Committee's terms of reference are to assess the risk to humans from micro-organisms that are used or occur in or on food and to advise the FSA on any matters relating to the microbiological safety of food.

In September 2005, the Health Protection Agency (HPA) alerted ACMSF members to a change in the epidemiology of human L. monocytogenes infection in England and Wales. This change was characterised by a doubling in reported cases since 2001, and could not be explained by outbreaks recognised during this time.

In Scotland in 2005 the incidence was also significantly higher than in 2004 and from the period 1993 to 1999. A lower increasing incidence was also reported in Northern Ireland. In all countries the disease occurred predominantly in older patients with bacteraemia in the absence of CNS infection.

HPA confirmed that the increase in listeriosis continued into 2007. Similar increases had also been reported in other European countries, including France and Germany.

In June 2007, ACMSF referred this issue to its ad hoc Group on Vulnerable Groups for consideration as a priority. The Group met on six occasions over a period of 16 months, to consider a series of hypotheses to examine the cause of the rise in listeriosis to inform the development of ACMSF advice to the FSA. The Group considered information on L. monocytogenes, including its survival, virulence and behaviour in food and the food chain. The epidemiology of the bacterium was reviewed, including transmission and trends in listeriosis in the UK, EU and other countries. Blood culture and sampling trends in the general population, including the elderly, were discussed and changes in clinical assessment in the over 60s were also considered. Other areas of investigation included surveillance of L. monocytogenes in foods, shelf life, changes in chilled food production and food safety controls.

The Group also examined social and behavioural factors in the over 65s, including data on food consumption patterns. Other factors affecting vulnerable groups were explored including underlying medical conditions and changes in vulnerable groups' care. Risk factors and underlying assumptions to assess whether the target population had become more susceptible to L. monocytogenes were evaluated and UK, EU and international consumer guidance on the risks posed by L. monocytogenes were reviewed.

The report
The ad hoc Group's draft report (Annex A) has now been adopted by the full ACMSF and can be found below for comment. The structure of the report is as follows:

• Chapter 1 summarises the background to the ACMSF’s deliberations and describe the Committee’s approach to its work
• Chapter 2 focuses on hazard identification and characterisation, including listeriosis in pregnancy and in non-pregnant individuals, the virulence of L. monocytogenes, the epidemiology of listeriosis and the changing pattern of human listeriosis in England and Wales
• Chapter 3 outlines the report’s rationale and the four main hypotheses to examined to try to identify the cause(s) of the increase in L.monocytogenes cases in the over 60s
• Chapter 4 considers the hypotheses to explain the increase in listeriosis cases
• Chapter 5 covers risk management including legislative limits, food industry controls and consumer advice
• Chapter 6 summarises the Committee’s conclusions and recommendations

The draft report also contains annexes outlining the Group's Terms of Reference and list of membership, analysis of consumption patterns in the over-65 age group, a list of tables and figures, glossaries of technical terms and abbreviations and a comprehensive reference section.

The key ACMSF recommendations are:

• Pan-European surveillance, epidemiological and microbiological investigations are recommended to investigate the increase in listeriosis in different Member States and to ascertain whether there are common generic or risk factors occurring in the UK and other countries. Studies to develop screening methods for L. monocytogenes isolates are also recommended to investigate differences in virulence and differences between isolates from different patient groups and time periods.
• Work should be undertaken to investigate whether the management of underlying conditions in the over 60s has contributed to the rise in listeriosis. Retrospective studies should be conducted to identify which underlying conditions are most associated with listeriosis in this age group.
• The amount of under-reporting (ascertainment ratio) for human listeriosis should be estimated.
• Collected data on cases of human listeriosis should include information on underlying comorbidities and their drug management.
• UK infection surveillance should be enhanced to incorporate data on denominator populations and numbers of medical investigations undertaken (including blood cultures).
• Work is needed to develop in vitro methods of investigating the frequency of specific genes or gene polymorphisms associated with difference in the pathogenicity of L. monocytogenes.
• Maintaining targeted active surveillance for Listeria spp. in foods is important to inform control of this organism. Such surveys should examine a wide range of foods (shopping basket surveys) and account for food purchases at catering and retail outlets.
• Information on food consumption patterns of the over 60s (including vulnerable groups) is needed to inform approaches to risk management. Behavioural studies are recommended on food handling, hygiene and storage behaviour in the home by this age group to inform understanding of potential factors contributing to the increasing the risk of listeriosis.
• General consumer food safety advice should be developed and communicated to the over 60s (including those in vulnerable groups), as well as to those who prepare and provide their food and those who provide medical advice about the risks of listeriosis to these groups. Studies should be carried out to evaluate the impact of such advice on these groups. Also the FSA is advised to refer this report to its expert Social Science Research Committee to consider the food behaviour, storage and handling practices of elderly people in the home.
• Any future advice to industry and enforcement authorities should reiterate the importance of temperature and shelf life control, hygiene/cleaning and formulation of food in preventing contamination or limiting the growth of L. monocytogenes in foods. Also the FSA should work with the food industry to ensure that formulations including salt levels of specific products are not changed without considering the impact of these changes on microbiological safety.
• As the provision of durability instructions such as 'Use by' dates on some perishable foods (chilled ready to eat foods) sold loose was found to be variable, a review of the need for consistent advice on such products is recommended.

Your comments
Your comments are invited on any aspects of the draft report and its recommendations. The ACMSF will review its draft report in the light of any comments received, before submitting a final version to the Chair of the FSA seeking her agreement to publication.

Further information
This consultation is not accompanied by an Impact Assessment because the ACMSF has no regulatory status. It is for the Food Standards Agency to decide whether to accept the recommendations outlined in this report and whether to produce an Impact Assessment should the recommendations be accepted.

This consultation has been prepared in accordance with the HM Government Code of Practice on Consultation, which states that a consultation must follow better regulation best practice, including carrying out an Impact Assessment (Regulatory Impact Assessment in Scotland). The assessment is included in the consultation documents.

We are interested in what you thought of this consultation and would therefore welcome your general feedback on both the consultation package and overall consultation process. If you would like to assist us to improve the quality of future consultations, please feel free to share your thoughts with us by using the consultation feedback questionnaire.

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If, after three months, the summary is still not showing, please contact the person who was responsible for the original consultation. Alternatively, you can contact Judith Taylor, the FSA Consultation Co-ordinator, on 020 7276 8633.
Email: judith.taylor@foodstandards.gsi.gov.uk