Invisible threat: Listeria in smoked fish

Date:
October 7, 2020
Source:
BfR Federal Institute for Risk Assessment
Summary:
Fish should be a regular component of our diets. It is an important
source of biologically high-quality and easily digestible protein,
minerals and vitamins. However, raw, smoked and cured fish products
also often contain pathogenic germs, notably listeria. People
can become infected by eating contaminated food and become ill
with listeriosis.



FULL STORY ==========================================================================
In 2018, 701 cases of severe invasive listeriosis were communicated to
the Robert Koch Institute (RKI), which translates into 0.8 cases per
100,000 inhabitants. Most listeriosis illnesses reported are severe and
are associated with blood poisoning, meningitis or miscarriages, for
example. In 2018, the disease was fatal in 5% of cases. Elderly people,
people with weakened immune defences, pregnant women and their new-born
babies are particularly vulnerable.

Listeria can be found in a large variety of foods of plant and animal
origin.

Cold or hot-smoked fish are often contaminated and are, therefore,
also suspected of transmitting this illness. Other fish products and
seafood eaten raw, such as sushi, sashimi and oysters or cured products
such as graved fish, may also be affected. "Pregnant women, elderly
people or those with weakened immune defences should only eat fish and
seafood that have been thoroughly heated," says BfR President Professor
Dr. Dr. Andreas Hensel.


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Not all Listeria bacteria cause illness. Of the 20 Listeria species
described, only Listeria (L.) monocytogenes is a significant cause of
infection in humans.

Infections during pregnancy can lead to miscarriage, premature birth, stillbirth or the birth of a sick child. Furthermore, listeriosis
mainly develops in people whose immune system is weakened by old age, pre-existing medical conditions or medication intake. They often suffer
from blood poisoning, encephalitis or meningitis as well as e.g. from endocarditis or bacterial joint inflammation. Listeriosis is associated
with relatively high mortality in risk groups. In healthy individuals
who do not belong to one of the risk groups, an infection can lead to inflammation of the gastrointestinal tract plus a fever, with progression generally being mild.

The bacterium L. monocytogenes is widespread in the environment and can
be found in many foods. High detection rates are found in minced meat,
raw meat dishes (e.g. tartare), raw sausage meat (e.g. "Mettwurst"
raw minced pork) and raw milk, for example. However, numerous other ready-to-eat foods of animal and plant origin, which are not subjected
to further germicidal treatment (e.g.

heating) after processing, may also contain L. monocytogenes. Examples
include cheese (made from raw or pasteurised milk), pre-cut salads
and vegetables, deli salads or sliced sausage products. This is because listeria can survive for a long time in food processing plants in recesses
that are difficult to reach for cleaning and disinfection. As a result,
the continuous entry of the germs during food production is possible.

Raw, smoked or cured fish products and seafood such as sushi, sashimi,
oysters, cold or hot smoked fish (e.g. smoked salmon) and cured fish
(e.g. graved salmon) are frequently contaminated with listeria. 7 to 18 %
of the samples of cold-smoked or cured fish products examined by the food monitoring authorities in Germany between 2007 and 2017, and 3 to 9 % of
the samples of hot-smoked fish products contained L. monocytogenes. Even
low germ concentrations are hazardous to risk groups, for example when
products are stored at home above the temperatures recommended by the manufacturer or when they are eaten after their best-before date. What's
more, handling contaminated products risks transferring listeria to
other foods.

The German Nutrition Society (DGE) recommends at least one fish meal every week. Fish notably contains special fatty acids and the long-chain omega-
3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).

The BfR recommends that people who have an increased risk of developing listeriosis should not generally avoid fish, but rather only eat fish or seafood that has been thoroughly heated. Listeria can be reliably killed
off by heating food to a core temperature of 70 DEGC for at least two
minutes. Risk groups should refrain from eating raw, smoked and cured
fish products and seafood.


========================================================================== Story Source: Materials provided by
BfR_Federal_Institute_for_Risk_Assessment. Note: Content may be edited
for style and length.


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Link to news story: https://www.sciencedaily.com/releases/2020/10/201007123057.htm

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