The plight of a California woman who just wanted to enjoy a nice salmon dinner serves as a public reminder that fish carry a variety of parasitic organisms, and if you don’t store and/or cook your aquatic entrée properly, you could be the next host.

As reported by The Mercury News, Felicia-Miracle Cipolla purchased 0.9 kilograms (2 pounds) of wild-caught salmon at the Richmond Costco in California on July 16. When she returned home and began putting away her groceries, Ms Cipolla and her family members noticed that something inside the plastic-wrapped package was squirming. A cell phone video documented the unnerving sight of a small translucent worm moving around in the filet.

In this case, the hitchhiking creature was identified as a nematode, or roundworm, though the exact species was not determined. Several types of roundworm complete their lifecycle in fish, marine mammals, or both, but the most common are those of the saltwater genus Anisakis. Though they have not evolved to reproduce successfully in a human, anisakids can colonize the human gastrointestinal tract when the larvae are accidentally introduced, causing a very unpleasant illness called anisakiasis.

The worms go through several developmental phases, hatching from free-drifting eggs into “second-stage” larvae that are then ingested by crustaceans. Inside the small invertebrates, the parasites mature into stage-three larvae, which find their way into the muscle tissue of salmon, herring, cod, mackerel, squid, sea bass, flounder, or other seafood species after their first host is eaten. Through this process of consumption and colonization, the larvae eventually make their way into to a predatory marine mammal, wherein they molt into egg-producing adult worms.

Only third-stage roundworms can take hold in the human gut; thus anisakiasis can arise whenever we eat fish, cephalopods, or shellfish that contain live larvae. Eating a seal or dolphin would be safe, but please don’t do that.

Characterized by severe abdominal pain, curing anisakiasis usually requires surgical removal of the worm(s). To avoid this fate, marine biologists and food safety researchers recommend always cooking seafood to at least 63°C (145°F) for 15 seconds. If you want to enjoy your seafood raw, they urge that you seek out sources that were commercially frozen for at least 15 hours prior to preparation or frozen in a residential freezer for a full seven days prior to preparation (commercial freezers are set to about -37°C or -35°F, residential units are much warmer) to ensure the parasites within have been killed.

And if you’re thinking, well maybe I’ll be OK because my fish doesn’t have any parasites, think again. According to the same group of experts: “Parasites are a natural occurrence, not contamination. They are as common in fish as insects are in fruits and vegetables.”

[H/T: Live Science]