You're probably eating worms and don't even realize it

When a video made the rounds of a New Jersey restaurant customer freaking out about a worm crawling out of a piece of fish, it made a lot of people's skin crawl.

The video is one of the many posted online by restaurant customers to call out restaurants when they don't meet expectations.

Stella Marina Bar & Restaurant in Asbury Park condemned the video on their Facebook page saying "the callousness and irresponsible reaction" was an attempt to "destroy" their reputation.

The original statement—which has since been taken down—went on to say, "It should, therefore, be emphasized that the presence of worms in fish offered for sale does not imply carelessness or bad practice on the part of the processor or retailer."

Worms in fish a common occurrence

As it turns out, the alleged infraction is pretty standard, particularly in fresh fish.

"It happens in halibut and a lot of the bottom fish. Lingcod, particularly," said Ann Best, owner of Oak Bay Seafood in Victoria. "The worms occur mostly around the belly cavity."

The worms in fish are usually small, white or almost clear in colour. In some fish, like cod, they may be more prominent and darker—like stray pieces of seaweed.

For employees at fish counters or fish processing plants, they're a common sight.

"If you're filleting a dozen fish in any given day, you're going to probably see worms in twenty per cent of them—if not more," said Best.

Parasitic roundworms, or nematodes, are so common that fish processors just cut out the infested bits and use the rest of the fish.

The worms have been linked to illnesses in rare cases when infested fish is raw or undercooked. But the danger goes away when the fish is cooked through or flash frozen before being served.

That's why fish used for sushi is previously frozen—never fresh. So is fish that is routinely cooked rare, like tuna.

Avoid getting sick from a worm

In either case, frozen or well cooked, you still may be consuming nematodes. They're just dead. It's a fact of life when it comes to fish, something fishmongers know well, but most consumers don't.

"We don't make a point of warning them. But we do try to make sure that all the areas where we know the likelihood of worms is high have been removed from the filet," said Best.

"Once or twice I have had people come and say, 'There's a worm in my salmon. What's going on?' And you simply have to explain: it's part of their natural environment. They occur in perfectly healthy, lively fish," she said.

The best way to avoid getting sick from consuming a worm in fish is to cook the fish thoroughly. If you're preparing a dish that requires raw seafood, like sushi or ceviche, ensure that you're using frozen fish labelled as sushi grade.