Carlos Solis
Salmon is many people’s favorite fish — we cure it at home, grill it, and serve it raw in sushi and tartare.
How a parasite gets into fish
Like other marine species such as cod and mackerel, salmon can carry worms from the Anisakis family. These parasites infect fish when the fish eats infected prey — krill, shrimp, or smaller fish. Later the larvae can migrate from the stomach into the fish’s muscle tissue.
Whether a fish contains Anisakis depends on whether it’s wild or farmed. Wild salmon encounter infected prey in the ocean; farmed salmon are usually raised in controlled pens and fed processed pellets, which greatly reduces the risk of infection.
For example, the Food Standards Agency in Scotland found no Anisakis in any of 720 farmed samples. At the same time, studies have reported high infection rates in wild fish — more than 60% of Norwegian samples contained the parasite.
What happens when someone eats infected fish
Anisakis matures and reproduces in marine mammals, but it dies in the human stomach. In humans, the larvae attach to the stomach or intestinal wall and trigger inflammation.
Symptoms appear within hours and may include:
- sharp abdominal pain, nausea, and vomiting;
- abdominal cramps, diarrhea, and sometimes blood or mucus in the stool;
- a mild fever;
- allergic reactions — rashes and itching; in rare cases anaphylaxis with swelling, difficulty breathing, dizziness, and loss of consciousness.
Which dishes carry the highest risk
The greatest danger comes from dishes where the fish is eaten raw or undercooked. High-risk foods include:
- sushi and sashimi;
- ceviche (raw fish cured in citrus juice);
- lightly cured or cold-smoked fish.
How to protect yourself
Food agencies warn that the risk comes from eating raw or undercooked fish. The most reliable ways to kill parasites are proper cooking and correct freezing.
- Cook fish to an internal temperature of 60 °C (140 °F) and hold that temperature for at least one minute.
- Freeze fish so its internal temperature reaches -20 °C (-4 °F) and stays at that temperature for at least 24 hours, or freeze to -35 °C (-31 °F) for at least 15 hours.
Inspect the fish carefully before you cook it. The parasite is fairly large and often coiled, so a close look at the muscle tissue will usually reveal it.
Sellers should visually check fish for parasites before they sell it, but the most reliable protection for consumers is proper cooking or meeting freezing requirements.
If you choose farmed salmon or a dish made from properly frozen or thoroughly cooked fish, your risk of Anisakis infection drops significantly. Still, be cautious when eating raw or lightly processed fish.
Based on material from the Daily Mail. Photo: Unsplash
