A fatal Listeria outbreak in the United Kingdom has been traced to a salmon-smoking processing factory in Scotland.

Food Standards Scotland (FSS) and the Food Standards Agency (FSA) have now named the company involved in the outbreak that has affected 15 people since October 2020 in England, Scotland, and Wales. Nine patients have become ill since January 2022, with many of them eating ready-to-eat smoked fish before falling sick.

Most patients are above 65 years old but one was a pregnant woman. Three people older than 65 have died and for two Listeria monocytogenes was a contributory cause of death. All cases had underlying health conditions.

Products positive at low levels
Lidl GB recalled Deluxe Oak Smoked Scottish Louch Trout and Lighthouse Bay Smoked Trout Trimmings, produced by St James Smokehouse. All use-by dates between Dec. 20, 2022, and Jan. 6, 2023, of Oak Smoked Scottish Louch Trout 100 grams and Lighthouse Bay Smoked Trout Trimmings 120 grams are affected.

In November, authorities said products had tested positive for Listeria but were within the maximum permitted level set in legislation. A limit of 100 colony Forming Units per gram (CFU/g) applies to foods that can support the growth of Listeria, during the product’s shelf-life.

Given the product was compliant with microbiological regulatory limits yet still posed a risk to vulnerable consumers, authorities said it was critical that interventions ensured enforcement of food safety controls as well as public health messaging so people can understand the risks.

A spokesperson for Food Standards Scotland said: “During testing, Listeria monocytogenes that matches the outbreak strain was found in products produced by St. James Smokehouse and sold by Lidl. The levels found have not been above-permitted limits, but the strain of Listeria has characteristics that make it more dangerous to vulnerable consumers.”

Advice to consumers
Junior Johnson, director of operations at the FSA, said an investigation into the outbreak identified a strain of Listeria monocytogenes which has caused serious illness.

“As we approach the peak of the festive season, we know consumers are more likely to eat smoked fish, such as smoked salmon and trout. While investigations into the outbreak continue, FSS and FSA are reminding vulnerable consumers of the advice more generally around consuming smoked fish — it must be heated until it is steaming hot before they eat it,” he said.

Johnson also praised Lidl for “doing the right thing” in taking the recall action.

Listeria is ubiquitous in the environment, and there is no stage in the production of cold smoked salmon that can eradicate the organism, so it is extremely difficult to reduce the risk to zero. Controls are focused on good hygiene practices to minimize the risk of contamination and ensuring shelf life does not allow the pathogen to reach levels capable of causing illness, said Food Standards Scotland.

Advice to people over the age of 65, pregnant women or people with weakened immune systems is they should thoroughly cook ready-to-eat smoked fish before eating it. The warning covers chilled smoked fish products that would not normally be cooked at home before being eaten.