Scotland mulls pathogen action levels

Food Standards Scotland (FSS) is considering introducing thresholds for action for some pathogens based on either a UK or Scottish approach.

Using targets based on reported infections of key pathogens could help monitor trends and be used as a trigger to act. However, figures would need to be interpreted carefully because of underreporting, inability to separate food and non-food sources, changes in demographics, and impacts of year to year fluctuations in environmental factors, such as weather.

When reported cases breach the threshold, different steps would be considered including an investigation to identify reasons behind the increase; additional food sampling associated with the pathogen and risk communication to consumers using tailored messages.

FSS currently uses Public Health Scotland data on confirmed laboratory reports for five pathogens to monitor how foodborne illness is changing.

Action level considerations
In April 2017, FSS published a strategy for reducing foodborne illness in Scotland. The focus was microbiological pathogens which have the highest disease burden in terms of incidence, symptom severity and mortality — Campylobacter, Salmonella, Shiga toxin producing E. coli (STEC), Listeria monocytogenes, and norovirus. Work so far has focused on Campylobacter, Listeria and STEC because Salmonella cases are often acquired abroad and many norovirus infections are because of person-to-person spread.

Year on year variation and the low number of reports for certain pathogens in Scotland has made it challenging to create appropriate threshold levels. However, the Food Standards Agency (FSA) has previously developed a trigger system for foodborne pathogens and is reviewing it.

Adoption of Scottish specific levels may be problematic for pathogens with lower case numbers, such as Listeria, where confirmed lab reports are generally less than 20 each year but UK-wide thresholds would need to be considered in a Scottish context.

Four other areas were identified in an update to the strategy: review and strengthen the uptake of interventions to support Campylobacter reduction; support businesses and consumers to minimize the risks of Listeria monocytogenes; understand the epidemiology of foodborne infection in Scotland; and improved targeting of consumer advice aimed at educating the public on the particular risks to vulnerable groups and how they can be avoided.

Work on specific pathogens
Campylobacter remains the biggest cause of bacterial foodborne disease. An FSS-funded source attribution study showed chicken-related strains were most commonly identified in human illness in Scotland.

FSS and FSA are developing a plan to understand how chicken contributes to infection rates, and where interventions need to be strengthened. Results of a survey on pathogens and antimicrobial resistance in retail chicken will be published later this year. Another mapping exercise will help understanding around interventions used in the food chain by farmers, processors and retailers to reduce contamination. Communication with caterers and consumers about the risks of Campylobacter in livers and duck meat and how to prepare them safely will also be a focus going forward.

Data from UK work suggests a reduction in high levels of contamination on chicken in recent years but very little change in the number of sick people or attribution to chicken related strains of Campylobacter.

During the past year, outbreaks and deaths associated with smoked fish and unpasteurized cheese have highlighted the technical challenges faced by small to medium sized producers in controlling Listeria. FSS is looking at risk communication to consumers and public sector procurement and provision of food in care settings.

As Listeria can persist in the production environment and grow at low temperatures there is a need for guidance on shelf life validation to ensure appropriate durability dates are applied, and on the sampling regimes required to verify the effectiveness of cleaning methods in removing Listeria from surfaces and equipment.

Scotland has the highest reported rate of STEC in the UK. In 2022, there were two nursery outbreaks, not caused by food, with 45 sickened because of E. coli O157 and 12 cases in a non-O157 outbreak. Another 26 patients were linked to a large UK-wide cluster for which no vehicle was identified.

FSS will also commission an independent review of the current definition of vulnerable groups, to determine if it can be refined based on up-to-date evidence on the range of underlying health and lifestyle factors that can make people in these groups more susceptible to illness. Findings will be used to support risk assessments and social research to identify communication methods that are most likely to reach the individuals that could be at increased risk.

The agency will continue to monitor trends in foodborne illness with Public Health Scotland and use any changes in reporting which could be having an impact on the figures to prioritize work.

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