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Salmon worms are squirming under the radar, for now

Nematodes pose a potential risk to wild seafood's reputation, but finding a solution in the supply chain remains elusive, and some say it's simply an accepted part of the business.

While farmed salmon often gets dinged for having sea lice, a common parasite in wild salmon commercially sold in the United States has kept its proverbial head down and, so far, it is low on the industry's list of concerns.

Anisakid nematodes can be found in anywhere from 1 to 10 percent of Pacific wild salmon commercially available for sale, according to Michael Ganzle, a food microbiologist at the University of Alberta in Canada, but there hasn't been enough of a focus research-wise on nematodes to determine whether the parasites have increased in salmon or not over the years.

"It's too small a level of significance in terms of public health," Ganzle said. "We don't track it for data because the thing is, [nematodes] are the most common thing there is in fish. They're in several different species other than salmonids."

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Nematodes are so common in wild salmon and pose so small of a health concern, they are not even listed in the Canadian Food Inspection Agency's reportable, immediate or annually, notifiable diseases.

Nematodes are, in fact, the most common parasite found in marine fishes, and anisakid nematodes are also present in major seafood items such as cod, herring and pollock, but are often easier to see in these fish than they are on salmon.

In general, anisakids pose minimal risk to human health. When ingested live in raw or under-cooked fish, they can invade the stomach wall or human intestines, according to the Center for Disease Control and Prevention (CDC), but the condition is rarely life threatening.

Losses and risk

At the retail level, the problem of nematodes should be of concern simply because it could become a public relations issue, Ganzle said. In July, he was interviewed by the CBC after a shopper posted a viral video of worms squiggling in salmon purchased from the retailer Save-On.

In the social media age, bad news travels with lighting speed. Several television stations have run reports in recent years about the discovery of nematodes in wild salmon, with Costco in particular a target. A quick search on YouTube returns results showing several amateur videos posted of worms squirming out of wild salmon sold at Costco and other retailers, with predictable consumer reactions.

"They're loaded with those parasites," one user says as he films, pointing out a squirming worm on a fresh Costco coho fillet. "When you go for tequila, that s***'s dead."

It's not a pretty sight, Ganzle said.

"Even though it may not be particularly dangerous, it can still be disgusting," he said.

It can also lead to losses and returned product. Retail buyers IntraFish spoke with gave mixed opinions on the severity of the nematode problem, but some wondered if it might be getting worse.

Resiliensea Group CEO Phil Gibson, a former Safeway seafood buyer, told IntraFish when he worked for the retailer, there was a zero-nematode policy promised by some suppliers.

"We required vendors to warrant they had eliminated anything with a worm in it," he said, noting the store still purchased a nematode-riddled fish maybe half a dozen times per year."

Patrick Wagner, who works in strategic sourcing for Seattle Fish Company, told IntraFish nematodes are part of his company's HACCP plan, "but we don’t do anything specific when purchasing," he added. "We just work with trusted suppliers so we know we are getting quality product."

Gibson said nematodes were a concern for groundfish more than salmon, and noted the issue never rose -- and still doesn't -- to more than a minor concern for consumers.

"In warmer months, such as July, August and September, that's when there are the highest incidents of nematode content in groundfish," he said. "When I was in retail, we avoided selling groundfish during those periods of time."

Nematodes in a haystack

The problem doesn't have an easy fix. Because nematodes are so common in wild salmon, it would be near-impossible to remove all of them before commercial consumption, according to Christina DeWitt, director of the Oregon State University seafood laboratory.

"The problem is even if you were trying to look for them, it would be really hard to find them all," she told IntraFish. "They're not always at the surface where you're cutting the fish. You would have to tear the fish apart, and some are invisible because they're so small."

The primary means of controlling the parasite, from a consumer point of view, is to either cook it or freeze it, she said. That's also the recommendation from the US Food and Drug Administration (FDA), which doesn't require but only offers guidelines for cooking and freezing temperatures to kill the parasites.

Mark Neely, who runs a seafood inspection business out of Bellingham, Washington, said that while they are nearly invisible to consumers on salmon, he sees nematodes on the salmon he inspects all of the time.

"If I find a couple of nematodes per fish, it doesn't alarm me at all, it's pretty normal," he told IntraFish.

Neely, who uses a dentist-like scraping tool to inspect the salmon, said he only cites the fish as unusual if he starts seeing five or more in a fillet.

"I don’t talk too much to friends or other people about parasites in fish because I don’t want to ruin seafood for them," he said. "I think that if most people think they are eating worms they won’t want to eat seafood."

""I think that if most people think they are eating worms they won’t want to eat seafood.""

Nematode screening and extraction is generally independent of salmon grading, Michael Kohan, seafood technical director with the Alaska Seafood Marketing Institute (ASMI), told IntraFish.

"However, processors have custom specifications for certain buyers that might include different grading specifications to meet buyer’s needs," she said.

All seafood producers in Alaska do comply with US federal codes on safe and sanitary processing as part of their Hazard Analysis and Critical Control Point (HACCP) plans, Kohan said.

Control measures recognized by FDA for killing parasites include freezing at -20°C (-4°F) for seven days, or cooking to an internal temperature of 63°C (145°F).

Solutions elusive, so far

Dennis Schreiber, CEO of Baader North America, told IntraFish there is no inspection process beyond candling -- shining a light through the fillet, which works for whitefish but not salmon -- to determine if nematodes are in wild fish.

"That is on our R&D list, but there's not an existing product specifically to detect nematodes," he said.

Schreiber said the issue is extremely important for the seafood industry to focus on because nematodes do impact the quality of seafood products and their value at the consumer level.

Marel told IntraFish it does not have equipment that detects nematodes, but it does have equipment to detect melanin and blood spots, trimming and skinning defects and levels of brown meat in fish fillets.

In 2010, researchers at the Norwegian Institute of Food, Fisheries and Aquaculture Research (Nofima), created a new system for spotting round worms in fish fillets with high precision at industrial speed. But the system, primarily created for cod, has not been adapted by the industry.

Karsten Heia, a senior scientist with the project, told IntraFish there has been no new activity on nematode detection since the system was introduced nearly a decade ago.

Keeping the parasites out of the supply chain, though, begins with processors and traders providing clean, carefully inspected fish.

Many US seafood processors rely on a method called candling, which involves examining fish fillets over lights. Candling can detects surface parasites, but it doesn't always find parasites embedded in deep in thick fillets or in dark tissue.

The bright side

DeWitt said one way to not be too grossed out by the prospect of eating a bunch of worms is to put it in context of all other foods. She noted wild salmon isn't the only product that gets sold to consumers with some additional "protein" in the mix. All living organisms, including farmed fish, can host parasites. Parasites are a natural occurrence, not a contamination, she explained. They are as common in fish as insects are in fruits and vegetables.

In peanut butter the FDA allows an average of 30 or more insect fragments per 100 grams, according to its site. The agency allows an average of 20 or more whole insects or equivalent in 100-pound bag siftings.

And that's not even getting into the amount of rodent droppings the FDA allows in popcorn and other everyday snacks.

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