Why can some fish be eaten raw?

Sushi: is raw fish healthy or dangerous?

There is a case in the media of a man from Portugal who caught an intestinal parasite while eating sushi. He came to the emergency room with stomach pain, vomiting and a fever. The doctors found a herring worm in his stomach lining. The parasite belongs to the group of roundworms. It is particularly common in sea fish around the world. Is it better to avoid raw fish?

The parasite is not called herring worm for nothing, because it infects around 70 percent of this type of fish. In Germany it is therefore mandatory that herring be frozen before processing. The parasite is carried away at minus 20 degrees.

How can you protect yourself from the parasite?

So far there have been cases of parasite infestation in raw fish, primarily in countries where fish is eaten raw or marinated. This is especially the case in Japan but also in Holland. According to the Robert Koch Institute, cases of illness are rarely observed in Germany.

The herring worm has not yet arrived in Germany

The consumer center in Berlin told t-online.de that in the past few years there had not been a single complaint after eating sushi that could be attributed to the worm. However, so far there is also no obligation to report, as is the case, for example, for an infection with Salmonella. Anyone who becomes infected with this bacterium must inform the local health department. The fact that this does not apply to the herring worm is a clear indication that it does not yet play a significant role in this country.

The roundworm freezes to death in Germany

In Germany and the entire European Union, sea fish must be subjected to freezing treatment. This is required by law. All larvae are killed in this way.

This applies to the following types:

  • herring
  • mackerel
  • sprat
  • Atlantic and Pacific wild salmon

The Bavarian State Office for Health and Food Safety examined sushi in Bavarian restaurants for roundworms from 2007 to 2014. The result: Larvae were not detected in any of the samples - neither living nor dead. This is certainly also due to the fact that farmed salmon is very often used for sushi, according to the investigation report. Due to the housing conditions, an infestation with the nematode is very unlikely in farmed salmon.

A disease caused by the parasite therefore hardly poses a risk in this country. The same applies to the member states of the EU. The prerequisite is of course that the grocer meet the requirement to freeze the fish for 24 hours at minus 20 degrees. However, the samples from several federal states give reason to be very confident.

How the parasite makes itself felt

If you catch the worm while on vacation in Japan, you should know that the incubation time until the first symptoms appear is between twelve and 48 hours after eating the infected fish. The penetration of the larvae into the mucous membranes of the stomach and intestines causes pain. Abdominal pain, nausea, vomiting and diarrhea are characteristic. In the course of the disease, inflammation can even lead to a rupture of the intestine.

Digestive problems can still occur even after the larvae have died (after about three weeks). There is no effective therapy against the worm. If the discomfort is too severe, it must be surgically removed.

Pregnant women, young children and the sick should be careful

For some risk groups, raw fish - regardless of the variety - can in principle become a danger. Pregnant women, for example, should generally avoid raw animal foods. Because the exposure to various pathogens is significantly higher than with processed food. Even people with weakened immune systems such as those infected with HIV and young children should avoid raw fish, meat and eggs.

Important NOTE: The information is in no way a substitute for professional advice or treatment by trained and recognized doctors. The contents of t-online cannot and must not be used to independently make diagnoses or start treatments.