A variety of parasitic infections might be acquired by ingesting raw or undercooked fin fish ( ). 1–3: You can get fish tapeworm, or Diphyllobothrium spp., by eating freshwater or anadromous fish that are raw or undercooked. Anadromous fish are sea fish that spawn in freshwater rivers, like salmon. Marinated and smoked fish can also transmit the worm. 4 Cases have gone down in places where it used to be common, probably because sewage treatment has gotten better. But cases have gone up in other parts of the developed world, probably because more people are eating raw fish. 4. Sushi (small pieces of cold cooked rice topped with fish, eggs, or vegetables and wrapped in seaweed) and sashimi (slices of raw fish) are very popular in Japan. Other popular dishes, like raw salted or marinated fillets (from Baltic and Scandinavian countries), carpaccio (very thin slices of raw fish popular in Italy), tartare maison (raw salmon) and poisson du lac façon nordique (in French-speaking Europe), and ceviche (lightly marinated fish in Latin America), may also be to blame. 4.
The eggs of Diphyllobothrium species hatch into embryos (coracidia) after 2 weeks in cool fresh water. These are eaten by copepods, which are the first intermediate host. For two to three weeks, they change into the first larval stage, called procercoids. When fish eat the copepod, the procercoids move into the fish’s muscle fibers and change into plerocercoids, the second stage of development. When a definitive host (a carnivore mammal like a bear, dog, or person) eats raw fish, the plerocercoids can attach to the small intestine wall. There they develop into the mature tapeworm over 3 to 5 weeks. Adult Diphyllobothrium spp. can be as long as 15 m, making it the biggest known parasite on humans. It can live for many years in the host’s intestine and lay a huge number of eggs every day, ending the cycle. 4,8,10.
Diphyllobothrium infections are often asymptomatic. When symptoms occur, they are often mild and vague, including fatigue, constipation, and poorly defined abdominal discomfort. Most lab tests come back normal, but some may show low vitamin B12 levels or frank pernicious anemia (if the worm is attached in the proximal small intestine, it can compete for vitamin B12 absorption). 4 People often notice they have an infection for the first time when they pass tapeworm segments in their stools5,7. This is what happened to the patient in this report, but their diarrhea could have been caused by an unrelated illness. Diagnosis is made by identification of ova or sometimes worm segments in the stool ( and ).
Treatment is usually 10 to 25 mg/kg of praziquantel given as a single dose. 4. An ova test in the stool should come back negative a week after treatment; sometimes a second dose is needed. 6: Treatment is usually finished in a single dose, but parts may keep coming out for a long time, which can be upsetting for patients and their families. If vitamin B12 levels are low, they generally return to normal ranges within a period of several months. 4: Praziquantel is not officially approved for this use in Canada, but it is the treatment that is always used. Niclosamide, 2 g as a single dose, is another accepted treatment, but it is not available in Canada.
On a population level, the cycle can be broken by good sewage treatment plants that stop it where eggs are dumped back into the water, since humans are the only ones who can survive. This is probably why diphyllobothriasis isn’t as common in places where it used to be common, like Scandinavia4 and the coast of Japan. 7.
On an individual level, consumers should be aware of the risks of diphyllobothriasis with consuming uncooked fish. No longer are sushi and sashimi only found in restaurants. They can also be found in the deli sections of many grocery stores. Marketers might want to put labels on the packages to reassure customers that the right steps have been taken to lower the risk of fish tapeworm. People who cook fish should know that cooking at 55°C for 5 minutes will kill the larvae. Freezing at -20°C for 7 days or flash freezing at 35°C for 15 hours, as long as the flesh is less than 15 cm thick, will also kill the larvae. 4,5,7,8 Sushi and sashimi chefs should use only fish frozen in this way. Public health rules require these freezing protocols, but it’s not easy for health inspectors to check that they are followed.
With sushi becoming more popular and easy to find in restaurants and grocery stores, it makes sense that the number of cases of diphyllobothriasis like this one would rise. Ching said that between the 1970s and early 1980s, there was a big rise in the number of cases in British Columbia. This was because more people were eating raw salmon. 11 A MEDLINE search with the words “sushi” and “diphyllobothria” turned up many case reports from all over the world, but only three of them were related to North America. In all cases, raw or undercooked fish were consumed, often salmon species, but sometimes perch, char, or pike. 5 Sushi and sashimi restaurants were specifically implicated in some reports. 7–9 Additional cases are likely occurring but are not being reported in the literature. Primary care physicians should keep the possibility in mind.
Since sushi and sashimi are very popular in North America right now and there aren’t many cases of diphyllobothriasis written about in North American literature, it’s possible that people generally follow the rules for properly freezing fish for these foods. But if a person has vague stomach problems or low vitamin B12 levels that can’t be explained, you might want to find out what kinds of fish they eat, especially since sushi and sashimi are so popular. You might also want to look for Diphyllobothrium ova in their stool.
Smoked salmon is a delicious and popular fish that can be found on appetizer platters, in salads, and as part of various entrees. However, some people have concerns about the potential for smoked salmon to contain harmful parasites. As a seafood lover and food safety advocate, I wanted to dig into this issue and provide a straightforward look at the facts around parasites in smoked salmon.
What Exactly Are Parasites?
Parasites are organisms that live in or on a host organism and get their food from or at the expense of the host When it comes to fish like salmon, there are a few types of parasites to be aware of
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Roundworms – These are worm-like parasites that can infect the muscles of fish They are one of the most common parasites found in fish,
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Tapeworms – These parasitic worms live in the intestines and can grow quite large, up to 30 feet long! Tapeworms in salmon are not common but can occasionally occur.
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Flukes – Flukes are a type of flatworm parasite that can infect certain parts of a fish like the liver or flesh.
It might not sound appealing to eat parasites, but not all parasites are very dangerous to human health. Proper handling and cooking of fish can kill many common parasites.
Can Smoking Kill Parasites in Salmon?
The good news is that the smoking process does help reduce the risk of parasites in salmon. Here’s why:
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The salt used in brining salmon hinders parasites. The brine basically dries out the meat, which makes it harder for parasites to grow.
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Smoking salmon exposes the fish to extended periods of heat. Maintaining temperatures at or above 145°F for at least 15 seconds can effectively kill parasites.
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Smoke contains compounds like formaldehyde that have anti-parasitic properties. The smoke helps create an environment that parasites can’t survive well in.
Even though smoking doesn’t completely get rid of all parasites, it makes the chance of getting them much lower. Commercially smoked salmon also usually goes through strict quality control and inspection procedures to make sure that parasites don’t get into it.
Purchasing and Handling Tips to Prevent Parasites
While the smoking process is effective at reducing parasites, there are some recommended handling steps you can take as well:
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Purchase smoked salmon from reputable sellers with high food safety standards. This helps decrease the risk of contamination.
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Check for any signs of spoilage like off odors, sliminess, or abnormal discoloration. Don’t eat smoked salmon that seems spoiled.
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Store smoked salmon properly in the refrigerator at 40°F or below. Consume within 1 week of opening for optimal freshness.
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Consider freezing smoked salmon for 7 days at -4°F or below before eating it. Freezing can kill any parasites that may be present.
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Cook smoked salmon thoroughly to an internal temperature of 145°F to kill potential parasites. Smoked salmon is often eaten without additional cooking, but giving it a quick sear or warming it through fully can offer extra assurance.
By following safe purchasing and handling practices, you can feel confident enjoying smoked salmon while minimizing the risk of parasites. Reputable brands and proper storage go a long way.
Frequently Asked Questions About Parasites in Smoked Salmon
There are a lot of common questions surrounding the concern of parasites in smoked salmon. Here I’ll break down some of the top FAQs with simple, factual answers:
Can you get parasites from smoked salmon?
It is possible but very unlikely to get parasites from commercially smoked salmon. The smoking process kills off most parasites, and freezing smoked salmon helps kill any remaining parasites.
What parasites can smoked salmon have?
The most common fish parasites like roundworms, tapeworms, and flukes can potentially be found in salmon before smoking. Thorough smoking at proper temperatures followed by freezing helps get rid of these parasites.
How do you know if smoked salmon has parasites?
Signs of parasites in smoked salmon include an off smell, abnormal soft or slimy texture, discoloration, or small specks or spots. Follow safe handling procedures and discard any smoked salmon with questionable signs.
Should you freeze smoked salmon before eating due to parasites?
Freezing smoked salmon for 7 days at -4°F or below can provide added assurance that any parasites are killed off before eating. However, this may not be necessary if you buy high-quality smoked salmon from a trusted source.
Can you see parasites in smoked salmon?
Most parasites in fish are not visible to the naked eye. Microscopic parasites can still be present even when smoked salmon looks normal. However, obvious signs of spoilage may indicate a parasite problem.
What happens if you eat smoked salmon with parasites?
Consuming smoked salmon with live parasites could potentially lead to symptoms like nausea, vomiting, diarrhea, and abdominal discomfort. Seek medical care if such symptoms arise after eating questionable smoked salmon.
How can you kill parasites in smoked salmon at home?
Aside from thorough cooking to 145°F and freezing for 7 days at -4°F or below, there are no reliable home methods to kill parasites in smoked salmon. Purchase high-quality smoked salmon and follow food safety guidelines for optimal protection.
Who Should Avoid Smoked Salmon Due to Parasites?
While the risk of parasites in smoked salmon is very low, there are some groups of people that may be advised to take extra precautions:
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Young children under 5 years old
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Pregnant women and their unborn babies
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Older adults with weakened immune systems
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Anyone with a compromised immune system or taking immunosuppressant medications
These individuals can consult their doctor about if they need to avoid smoked salmon or any higher-risk fish entirely. If consuming smoked salmon, following the safe purchasing and handling steps outlined in this article is particularly important. Freezing before use provides an added layer of protection as well.
The Takeaway on Parasites and Smoked Salmon
When handled properly, the risk of parasites in high-quality, commercially smoked salmon is extremely low. The smoking and freezing process work to kill off any potential parasite contamination, and safe handling prevents reintroduction of parasites. While not 100% guaranteed to be parasite-free, smoked salmon can be enjoyed as part of a healthy diet when basic food safety precautions are followed. As a seafood lover myself, I’ll continue to enjoy smoked salmon in moderation as part of an overall balanced lifestyle.
