Salmon can contain parasites, a natural occurrence in many wild fish. Modern food handling and preparation methods significantly reduce any risk associated with consuming salmon. Understanding these factors helps consumers enjoy salmon safely.
Common Parasites in Salmon
Two primary parasites sometimes found in salmon that can affect humans are Anisakis simplex (herring worm) and Diphyllobothrium latum (broad fish tapeworm). Anisakis larvae typically enter salmon when they consume infected marine invertebrates like krill. The Anisakis life cycle involves marine mammals as definitive hosts, where the worms reproduce and release eggs into the ocean.
Diphyllobothrium latum has a more complex life cycle, involving crustaceans and freshwater fish, which salmon can encounter during their migratory phases. These parasites are generally more prevalent in wild-caught salmon due to their natural feeding habits and exposure to diverse aquatic environments. In contrast, farmed salmon, often raised on processed feed in controlled environments, typically exhibit a lower risk of these parasites.
Preventing Parasite Transmission
Effective methods exist to eliminate parasites in salmon, making it safe for consumption. Cooking salmon to an internal temperature of 145°F (63°C) is recommended by the USDA, which effectively kills any potential parasites. Using a food thermometer inserted into the thickest part of the fish ensures this temperature is reached.
Freezing is another reliable method for parasite destruction, particularly for fish intended for raw or lightly cooked dishes. The FDA recommends specific freezing parameters: holding fish at -4°F (-20°C) or below for 7 days; freezing at -31°F (-35°C) or below until solid, then holding at that temperature for at least 15 hours; or freezing at -31°F (-35°C) until solid, then storing at -4°F (-20°C) or below for 24 hours. These conditions are routinely applied commercially for “sushi-grade” fish, ensuring safety for raw consumption.
What Happens If You Ingest Parasites?
Ingesting live parasites from salmon can lead to health implications, though such occurrences are infrequent due to safety regulations. Anisakis larvae ingestion can lead to anisakiasis, characterized by symptoms like sudden, severe abdominal pain, nausea, vomiting, diarrhea, and sometimes allergic reactions such as hives. Symptoms typically appear within hours of consuming the infected fish.
Diphyllobothrium latum symptoms are often mild or absent, but can include abdominal discomfort, diarrhea, and weight loss. This tapeworm can absorb vitamin B12 from the host, which can lead to a deficiency and, in some cases, a type of anemia. These infections are generally treatable; Anisakis larvae may be removed endoscopically, and tapeworm infections typically respond to anti-parasitic medications.