Friday, September 22, 2006

Parasites in Fish, Part 1 -- Cod worm


This video is a June 2013 update to the original post.

If you've been reading this blog for the past couple of months (or even days), you probably came to expect something appetizing from it. Well, I have news for you folks. The next few posts might shatter your perception of Beyond Salmon for I am embarking on a "Parasites in Fish" series and there is no way I can make this lovely topic appetizing.

Why has a girl that almost flunked biology in high school got so interested in parasites? Sushi of course! Oh, and tartar. And ceviche, too. It’s amazing what I’ll do for raw fish. I've been buying tuna, salmon, and branzino from New Deal to serve raw for over a year and when I tried to go back to restaurant sushi recently, I realized that I've been spoiled for life. New Deal's fish is just better. The question is how much of a risk am I taking by serving raw fish at home?

If you are a squeamish person, new to cooking fish, I suggest that you don't read any further. I had a woman, in one of my classes, tell me that she wouldn’t eat fish again after my little lecture on parasites, and I don't want to be responsible for people stopping to eat fish purely because of squeamishness. If you are cooking the fish (with heat), no harm will come to you. I promise.

No mater how hard I looked, it was hard to find solid information on this topic. FDA was passionate about scaring the media, and the media was passionate about scaring the consumers. What I needed to find was someone passionate about parasites, and after 20 unsuccessful Google queries, I finally figured out what to search for: "parasitology Ph.D." Yes, there are people who care about parasites as much as I care about food and after a few e-mails, I had interviews lined up with 2 prominent parasitologists, Dr. Palm from Institute for Zoomorphology, Cell Biology and Parasitology in Düsseldorf, Germany and Dr. Gardner from Harold W. Manter Laboratory of Parasitology at the University of Nebraska.

First of all, let me say that parasitologists are some of the kindest and most patient people I have ever met in academia. They were willing to explain fish parasites in terms that even I could understand and painstakingly answered all my questions. I learned that there are over a hundred species of parasites that can be found in fish, but only 3 of them are potentially harmful to humans: Pseudoterranova decipiens (a.k.a. “cod worm” or “seal worm”), Anisakis Simplex, and Tapeworm.

Today, our special guest will be cod worm. I remember my first encounter with this critter about 4 years ago. As I unwrapped a cod fillet, I was greeted by a little worm squirming out of the fish. Good thing I heard about these worms before, or I would have thrown the fish in the trash and never set foot into that fish market (actually, it happened to be Whole Foods). In spite of my initial disgust (I am the kind of person who screams at the sight of an itsy-bitsy spider), I inspected the fillet, removed the worms and cooked the fish. It tasted just fine, and as you can see, I lived to tell the tale. These little worms are the pain of any fishmonger's existence because they freak the hell out of consumers. They are particularly common in white fish (cod, haddock, flounder, sole, and halibut), but I've also seen them in swordfish and monkfish. How often do you see them as a consumer? I cook fish at least 3 times a week and I'll see them a few times a year.

To prevent us, consumers, from having to look at these unsightly animals, the fish processors put all white fish through a process called "candling." They put the fillets on glass sitting over a lamp. This allows them to see through the fillet and remove any visible parasites. Think about this process as an airport inspection -- it makes everyone feel better, but it's not foolproof. On occasion, a few worms can escape the inspection and travel from the fish processing facility to your fishmonger and then to your kitchen. If this happens to you, don't panic. Remove the worms, and cook your fish the usual way. If you don't want to cook your fish after seeing the worms, I quite understand. Just don't go out of your way to ruin the fishmonger's reputation. The presence of worms has nothing to do with the freshness of the fish and I assure you that your fishmonger tried his or her hardest to protect you from this terrible experience. Last thing they want to happen is for you to find worms in your fish, but unfortunately this does happen sometimes.

What happens if you eat a cod worm? If it's dead, which it's bound to be if you cooked your fish to opaque state (or 140F), nothing at all happens. Even if you prefer your fish cooked a little less (120-130F) like I do, the odds of you eating a live worm are very slim. It would have to be a really hardy worm to survive those temperatures. If you are serving fish raw, and one of those guys manages to stay intact after you sliced the fish, and makes it all the way to your tummy intact, you are in trouble. Your stomach will eventually kill them, but since they originate in seals, they can get quite comfy in any mammal including us humans making the experience extremely unpleasant. As Dr. Palm puts it, “It is better not to eat them alive.”

What does this mean to serving fish raw or cured? That’s a topic that deserves its own post, so stay tuned.

You might also want to see these Frequently Asked Questions that people ask me about cod worms.

p.s. On a happier note… I’ll be away in California on vacation starting tomorrow, but I look forward to responding to all your questions and comments and telling you more parasite stories when I get back.

Parasites in Fish, Part 2 -- Anisakis and Tapeworm

163 comments:

5penny said...

Hi, I came from simply recipes for the pate brisee advice and am staying for the parasite stories. I'm not really a huge fish eater, but I apparently am my grandmother as I now prefer to read about food preparation, haha. Insightful and delicious site!

ilva said...

Great and interesting topic, it's important to learn about these things as well. I'm quite squeamish but I prefer to know about the dangers and how to deal with them! Thanks Helen! I hope you are enjoying California!

Magda said...

It takes a passionate and talented writer to turn a lesson on parasites into something that reads like a detective story! I can't wait for the next installment.

And, lazy cook as I am, I made the carrot stuffing for eggplant last night and it's wonderful! I'll do the eggplant today. Thanks!

Michele said...

What might happen IF one did happen to survive and take residence in your stomach?

Amy said...

Oh I wish I hadn't read this just now. Any other time, I would have wanted to know more about parasites in fish, but I am making seared tuna for dinner. I might have to have an extra glass of wine. Cheers!

Dianka said...

Wow, what an important topic, given that we eat fish more and more these days. You never can be too careful! Have fun in California!

tsduff said...

I live here in sunny California, and once I ordered sushi to-go at a high-end sushi restaurant. Inside, I had been served a piece of tuna with a wriggling, very narrow (like a pin) pink worm. I don't know what kind of worm it was, but obviously it grossed me out and I threw out the entire lunch. I have never been back to that eating establishment. It seems to me you would see a worm in the fish while slicing it for nigari! I still adore fish, and eat it all ways, including raw. I just look carefully before taking a bite! Good post.

shawn said...

Oh, definitely such a diversion. But don't worry, I'd still read all of your parasite series. It's more of the learning actually that I'd stumble upon your blog once in a while. Keep it up!

veuveclicquot said...

wow. that was instructive. thankfully i'm not squeamish!! looking forward to learning more about this topic.

hope you're having a blast in california!

Culinarily Curious said...

I'm also new here, and as a sushi and rare-fish lover, I'm going to get as much if not more out of your parasite series as your more appetizing topics. Thank you for taking the time to share your knowledge with us.

Duane said...

That's creepy. But it won't stop me from eating fish. I may think twice before eating any raw fish though.

Anonymous said...

Haven't experienced cod worms yet, I may well avoid cod but I actually don't order it very often (I get dried cod more often than fresh).

Like your blog.

Stephanie said...

Helen, very useful post, thanks. Is there a specific way you remove them? I'm thinking of ticks, how you light a match on their rear end so they scramble out instead of ripping them off and leaving their head buried in. Or like the method of removing a leech (yes, I know that from personal experience too). How did you remove the worms? Just a pair of kitchen tweezers like you use to remove pin-bones?

Anonymous said...

I love fresh fish and food! However, when i went to the supermarket today in the UK and bought some fresh cod i was disturbed to see the end of a worm wriggling inside the cod! I normally am sqeamish but this time i was intrigued! I called the supermarket straight away and they said cod worms were common and just to cook the fish thoroughly. I was not convinced! Hence, searching for more info landed me on your blog! Satisfied customer now but still questioning whether i should take it back to the supermarket or just enjoy the cod (without the worm, of course)! Thanks again!

Helen said...

Hi Anonymous,

Most supermarkets in US will gladly exchange the fish or give you a refund if you found a worm in it. As you probably have already learned from the article, the worms are not in the fish because it's not fresh. Friends of mine who go fishing told me they found them in fish that was just pulled out of the water. Your supermarket is correct that if you cook the fish through, they are harmless to your healthy. Don't get carried away with "cooking it through." 10 minutes per inch of thickness at 450F will be sufficient. But I know what you mean about them being just plain ikky. Whenever I get them in my fish, I lose appetite too.

Cheers,
-Helen

AMW said...

I think I am a cod worm magnet! I recently bought wild snapper and was greeted by a squiggling live worm upon opening the package. Disgusting! Then, after a month's recovery, I decided to spend even more money and taxi fare, and bought 2 large wild cod fillets. I just sat down to a big curly cooked worm in the flesh of my flakey perfectly cooked cod. I called the store and read them the riot act, then found your blog on my Google search. I don't want to throw out my fish, but I can't imagine eating it again this week. ICK! Thanks for your post.

Helen said...

AMW,

I feel for you! Worms and fish are really icky looking. If you need a little recovery time before trying cod again, here are some normally worm-free fish:

-tuna
-salmon
-branzino
-orata (sea bream)
-baramundi
-trout
-tilapia

Cheers,
-Helen

Anonymous said...

i found a 2cm long,pink/red worm in a fillet of perfectly well cooked cod.Was this a cod worm?i had no idea that worms could be found in the flesh of fish!

Helen said...

Hi Anonymous,

Yes, you found a cod worm. Since the fish was cooked, you were completely safe to eat it (I mean the fish, not the worm.) You could of course eat the worm too, but I know few people who find them appetizing ;)

Cheers,
-Helen

lafaz said...

Very interesting topic. I represent from a chilled tuna processing factory. I have seen a parasite in tuna which is invisible during candling but appear later on. We cant help in such situation.
What do you think about the Sashimi (raw eaten fish)? Japanese are so fond of sashimi and its getting popular in other countries too. The only preventive method is to blast freeze the fish before eating. Keep writing, Regards/Lafaz

Helen said...

Hi Lafaz,

Welcome to Beyond Salmon. there is a ton of info here on serving fin fish raw, so browse around and have fun.

Here are some links to get you started:

Serving Fish Raw

Tale of Two Tunas

Cheers,
-Helen

Maria said...

Hi: Found a 3 cm worm on a wild alaskan cod filet bought this Easter weekend from Costco. I feel extremely squeamish at the sight of one, especially when I love fish. I then called them immediately and was told that it is quite common in cod, and I could choose to eat it or return it. Well, I chose to return it and bought home a worm free Halibut filet.

Helen said...

Hi Maria,

Switching cod for halibut -- I'll take that exchange any time :)

Cheers,
-Helen

Anonymous said...

HI..MY FIANCEE JUST PULLED OUT A DARK LOOKING COILED UP WORM IN OUR SALMON....ITS ABOUT AN INCH LONG WHEN UNCOILED...THE FISH WAS BAUGHT FROM TESCOS IN A READY MEAL BOX THE KIND YOU TAKE HOME AND FREEZE AND THEN OVEN COOK IT WAS COOKED AT 200C FOR 35MINS ...SHE GOT LUCKY AND NOTICED IT BEFORE EATING IT BUT ME ON THE OTHER HAND EAT QUICKLY AND DIDNT LOOK THROUGH MY FISH AS I ATE IT..WHAT IF I ATE ONE ANYBODY NO WHAT KIND OF WORM IS IN THE SALMON AND IS IT DANGEROUS..THANK YOU

Helen said...

Hi Anonymous,

All worms in absolutely all fish are completely harmless if the fish is cooked (yes, even if you ate a worm). So unless you are eating fish raw, you don't have to worry about them.

Cheers,
-Helen

Marijhaa said...

Hey, I’m another Tesco’s fan on this blog! Yes, that was until I bought a couple of Mackerel fillets. They were infested with these skinny milky colour see-through one inch long coiled warms. That was extremely disgusting! Despite that I got my refund, I would still like to know if that is normal, as all warms described on this blog seem to look different. Cheers! PS: if this is to be expected when you buy fish, should there not be a warning on the package?

Helen said...

Hi Marijhaa ,

There are hundreds of different fish parasite species and they all look different. What you found in mackerel is "normal", but that doesn't make it any less freaky for you I bet. Rest assured that this level of infestation is unusual and it doesn't mean that mackerel is normally wormy.

Why is there no warning on fish? Hmm, good question. I guess that it's because these icky creatures don't pose any danger if you cook the fish. Besides, would you buy fish if it had a warning on it about possible worms? I am not suggesting you cook this wormy fish just because it's harmless -- if you are disgusted, you won't want to eat it anyway. Returning it to the store for a refund is reasonable, just don't give them a terrible time about it. If the fish was sold whole, there is nothing they could have done to prevent it.

Here is an interesting comparison. This weekend I bought some lovely wild mushrooms. Chanterelles were fine, but morels were crawling with worms when I cut them in half. I was totally disgusted and asked my husband to help me remove the worms. He tried for a while, but then we realized that there are just too many of them and we threw all the morels out. I was not upset at the store in any way. When you buy wild mushrooms, you have to expect that to happen sometimes. And no, there was no warning saying "wild mushrooms might have worms" :)

Keep in mind that humans are not the only ones who like fish, mushrooms, apples, raspberries, corn, etc. There are plenty of living creatures that wouldn't mind getting there first and unless we get some serious chemicals involved, we have to put up with a bit of ickiness once in a while.

Cheers,
-Helen

John said...

The very reason I'm browsing this website is because I've just found one little worm in my fresh cod. Exellent website, thanks for the tips...

Laura said...

What a wonderful and informative article. I can't say how much I appreciate it after we found our first worm last night in our fresh cod. Does anyone know where we can find photos of the little squirmers? I would like to compare to make sure that I am making the correct I.D. My husband and I had a hard time eating even veggies last night after seeing the worm. But, I am not going to lie, after reading this article, I think I might pull the baby out, pull out the worm(s?), and enjoy the fillet.

Thank you again!

Laura said...

What a wonderful and informative article. I can't say how much I appreciate it after we found our first worm last night in our fresh cod. Does anyone know where we can find photos of the little squirmers? I would like to compare to make sure that I am making the correct I.D. My husband and I had a hard time eating even veggies last night after seeing the worm. But, I am not going to lie, after reading this article, I think I might pull the baby out, pull out the worm(s?), and enjoy the fillet.

Thank you again!

Helen said...

Hi Laura,

Here are some pictures of worms. Sorry, not very appetizing ;)

Cheers,
-Helen

Jeff said...

Got us tonight! Cod from Whole Foods here in Boston - found a single wriggling worm. Went online, read this and other articles and got the fortitude to go ahead and cook it.

Thanks for the info.

PAL said...

I had the same worm experience while eating Costco fresh flounder. Look at it on:

http://palofgfc.blogspot.com/
(Oct 3, 2007 posting)

Anonymous said...

Thanks for sharing this information. I just bought some cod and while waiting for it to marinade, i noticed something like a bone sticking out (i had to remove a bone before slicing it). But the "bone" started moving. It freaked me out. I have phobia towards worms. I wanna cry. But I knew that there are worms in big deep see fish, especially Salmon, which was told to me by a chinese chef.

Anyways, I haven't decided what to do yet. My stomach completely turned. I think I'd better start reading your other blogs.

Koe

connie ruhe said...

As a manager of a high-end meat market with a fresh fish department I can tell you that these worms are found in many fish. When chilled, they stay tightly coiled within the flesh of the fish. As they warm up, they come wriggling out to be seen. Quite a fright in the seafood display case. We learned that yes, they are harmless to humans and we probably eat a lot of them. A quick visual inspection in front of a light bulb would reveal their hiding places so they can be removed.

I suspect that these worms would flee the fish after being caught if the fisherman did not ice their catch immediately.

So, I can put up with a few little redworms now and then, knowing my fish is safer having been iced right away.

Anonymous said...

Yes, I almost gave up a good thing by no longer eating nutritional fish having recently seen a cod worm. Not squeemish, but that sort of got me. I decided not to let the experience ruin many more years of beneficial fish eating. And figured it must be fairly common. Decided to use the wonderful internet - googled and found this very nice blog! Thanks!
Another WholeFoods cod piece, but not stopping me from continuing on. Feel more comforted now knowing it's ok and just make sure to cook it. Remove the worm, stopping thinking about it, cook and enjoy.
Like anything in life, careful what we think about/focus on.

I do wonder about eggs though. Are there any? Would handling the fish when raw affecting you?
I think we can get obsessive about this stuff though. I'm sure we take in alot more ickyness than we think and we are obviously fine.

Thanks again all for sharing experiences! The beneficial sides of the net. :)

Helen said...

Hi there,

Don't worry about eggs. There can't be any because the worms can't reproduce in fish. They need a mammal host for that.

Cheers,
-Helen

Anonymous said...

Thanks Helen, I would have never guessed about the egss. Interesting. But - I just had cod again and of course really inspected while eating and I just have to be done with it. I thought I inspected well once it was fresh, never to think they would be burrowed deep in the fairly tough flesh. When I was eating, I noticed a tiny nub sticking out of piece of those layers you get when the fish is cooked. I though, nah! this can't be one. I tugged at and it unveiled to be a fairly large coiled up worm all imbedded in there. Then another one. I just gave up.
I am usually strong with ucky stuff, having even eating bugs and oddities from street vendors in Asia, but I just can't seem to get past this thing of the worms in the nice piece of bright white cod. It's strange, I think if it was on my veggies I would not be as turned off. It's almost something psyhc about a worm in a delicate piece of bright white meat.
As I said in my last comment, I really do not want to give up the health benefits of fish. I think I will try a compromise and go with one of the non (or much less) parasitic fish you mentioned. I imagine all living things would have some sort of those buggers, but I gather as you researched, should be less. And googling, I see cod is more popular to have them.
I noticed a fish or two you list in the safer list, some have commented here I think indicating finding a worm, maybe salmon or haddock. Not sure. But a fish or two in that safer list also have very very low mercury levels, so that's good too!

Ok, needed to vent a bit again about this experience. When I cook and eat chicken or beef, it's a much smoother experience. Not sure why - seems hardier and cooks better and you typically don't have the bad visual experience ruining your appetite. I'm sure they're there, but it's sort of the "what you don't see..." type thing.
And of course veggies are a breeze, even with some tiny nymphs or whatnot on the lettuce. No probs eating a few of those.
I think it's the whole "parasite" "worms" thing and actually seeing them!

Thanks for all the contribution of info. Have a nice day!

Helen said...

Hi there again!

If you'd like to avoid parasite prone fish, stay away from haddock. It's in the cod family and is very prone to worms. So is sole, flounder, swordfish, and halibut.

Salmon is normally "clean", so is tuna, branzino, orata, farm-raised trout, tilapia, striped bass, sable.

Anonymous said...

Just spend an hour and a half cleaning worms out of two cod pieces. I believe it was a large family. Or may be two. They were in packs, small and big. I understand that stores can't possibly clean all of the worms out, but this cod looked like a worm factory. Are there any regulations about something like this?

Helen said...

I don't think there are any regulations about worms in fish. I do agree with you that a whole "family" of worms is a bit too much. The fishmonger who sold you the fish should have noticed and not sold you this piece.

Cheers,
-Helen

Fryeguy68 said...

Just caught 9 cod and 1 haddock on Friday, 4 more cod last night and going again tomorrow. So I can't say that these little worms bother me and love the thought of filling my freezer.. BUT, I am curious about knowing the answer to the question above, "What could one of these worms do if they happen to survive and make it to your tummy..?"

Thanks much,
Fish On!!!

Helen said...

if you are cooking the fish, they will NOT survive, so don't worry. Cod and haddock should always be cooked, so it shouldn't be an issue for you. For what happens if they make it to your stomach alive, check with your doctor. I hear it's stomach flu type symptoms, and depending on the parasite type they can be more or less serious.

Anonymous said...

hi thanks for such an informative blog- came across it while trying to find out whether those roundy coiled things i found in my fresh cod were worms...disgusting! i tried to convince myself for a while that really it was just the elaborate venous system in the fish [they looked like coiled veins] unfortunately i now know that they are worms yuck ! inspite of what you say i have this last few minutes turned into a vegetarian ... i have been avoiding meat for a long while ever since my sister picked up an intestinal parasite from meat [fish?] and her health has been so bad since ! i just hope youre right about them not being able to do damage when dead ...and hope they were dead when i ingested them !! disgusting !thanks again.

Anonymous said...

hello, last night i was out at dinner and ordered a ceviche, as i was eating the raw halibut i found a small white worm in the meat of the fish. I am now worried that there were more worms and they now might be feasting in my tummy! Could you tell me what happens if this was a codworm that I ate that was stilll alive?

PLEASE HELP

Helen said...

Hi Anonymous,

it's best to talk to your doctor. The acidity in the marinade is likely to weaken the worms so they probably won't survive in you, but I am not a medical authority.

Cheers,
-Helen

bebs said...

Hello! I bought a whole fillet of salmon from the fresh market I usually go to for seafoods, took off and went to a couple of errands before going home, of course, they put a bag of ice in the bag with the salmon. I got surprise when I opened the bag and saw a squirming tiny little worm on the fillet. I called them and they said most fishes got worms and that they don't pose danger to our health, I throw the little creature and sealed the fillet and put it in the freezer. Now tell me, is it still safe to eat it? I love salmon. Please enlighten me on this, it was my first encounter on such thing.

Helen said...

yes, your salmon is perfectly safe. if anything, freezing would make it even "safer" since it kills parasites, but unless you are planning to eat it raw, it makes no difference, since cooking kills parasites too.

Anonymous said...

After reading this I have decided to go ahead and cook my halibut despite my initial disgust at seeing 3 pink worms on the fillets (and those are just the ones I can see before I take them out of the plastic wrapping)Now that I know its not uncommon I will try to be brave...!

Anonymous said...

Thank you so much for your information on cod worms. I have just had my first experience of these devils after buying a cod fillet in Morrisons. Whilst frying the fish, my dog dribbling at my feet, I saw what I thought was a bruise on a flake of fish and dropped it for the dog. I finished cooking the fish and served up only to find the same round pinkish blob on some flakes whilst eating. I cut them open to find coiled up worms (4 in all). I felt sick and immediately looked on the web to look up cod worms. I am only hoping now that the fish was cooked through when I gave some to the dog. Time will tell, but I do feel more relieved to know that if I did eat one and hopefully it was dead I will survive to tell the tale. Thanks again for a great site and peace of mind.

Anonymous said...

"Rad" Fish?
No, not rad-ical, ir-radiated.
I used to go with the rad-opinion that irradiated food is a bad
idea. Not sure anymore,
maybe irradiated veggies and fish
could be made parasite free
without injuring the aesthetics or
food value of the foods?

Helen said...

would you really rather eat fish treated with radiation than put up with a few innocent worms? I know they are kind of icky looking, but they really are totally harmless if you are cooking your fish. I doubt too many people eat fish raw at home and those who do should learn a good bit about fish to do this safely. keep in mind that most organic apples that are not sprayed to death with harmful chemicals can on occasion have a little worm in them too.

Anonymous said...

I got onto this ''worm trail''
via an obit that mentioned the
cause of death as complications
from surgery for Echinococcosis.
(Apparently the parasitic monsters
in the Alien* films are only
slight exaggerations of earthly
phenomena) A simple salad, or
touching a 'canid' could launch
the process. Later I started
looking up 'parasites fish' etc.
and eventually found my way to your
blog. I think I need to retreat to
the Food Network and just look
at the fusion recipe photos
for Vietnamese French Fries 9 ways
or some other reality check to get
my attention off those ubiquitous worms!!! (-;

Bebie said...

Hmmmm....I am not in favor to that kind of treatment (radiation)for food , could we still get the same nutrient from food?? I doubt we could, why would we do it that way anyway? Why can't we just accept the fact that there are tiny little creatures in our food before it reach in our mouths? We do want to live longer, right? As for eating fish, yes, I love ceviche the way we prepare it in my country, I love it when it is soaked with the spices and vinegar very well before I eat it, that way I know it is "cooked". for some they don't want it that way but I enjoy it anyway.

Having trouble understanding the parasites in our food is quiet a big question to most of us. All I can say is cook your food well especially meat and seafoods, don't listen to some people telling you about your cooking as long as you know what you are doing then go for it and enjoy your meal.

Kim Lyle said...

Last week I went on an Off-Shore fishing trip off Long Island New York. We went on a Cod fishing trip. I caught several Sea Bass and Ling fish. My brother caught a Cod fish and the fish was loaded with worms. This absoultely turned my stomach. After this experience, I will never eat any kind of fish again even from White Castle's. You could see a brown spot in the meat of the fish. When you removed the top of the spot, several worms sprung-out like slinkys. I've been fishing and eating fish for over 40 years. I may continue fishing, but as far as consuming fish again, that will never happen again. Kim - Jersey City, NJ

Helen Mac said...

Wish I'd read this BEFORE the event! I bought cod from my local fish counter at the supermarket, it was trayed and cling wrapped. I took it from the fridge to steam and use for fish cakes, when I saw a thread. It wasn't a thread...it moved, sending my stomach into paroxysms of squeamishness, the fish, packet and all went flying into the bin. I called the store to complain, the staff were grossed out, except The Fishmonger. He explained how common it was, and that I should go ahead and cook the fish, he was stunned when I gagged over the phone. I live in Scotland, East Coast, am 60+, have always eaten fish, and never seen one before. Fish isn't part of our diet right now, eating more and more veggies these days! Thanks for all the info, my stomach is churning as I write!!

Helen Mac said...

Very informative article, although it grossed me out!

Anonymous said...

I recently purchassed a bag of frozen Flounder indivual rapped fillets. Some of the fillets had little circles on them. I thawed the fish in the micro then put flouer and a little corn meal to coat and fried each till well done. Some of the coating came off in spots and I could view one of the round circles. I had to look twice at it to make sure what I was looking at. It was a small string like redish brown in color in the center of the circle and it was unwinding and moving out of the circle. How can this be if this thing was completly frozen then defrosted and fried till a little over done. What kind of a worm can survive the freezing and then fried???? What happens to me if I had eaten any?????

Helen said...

Dear Anonymous,

Please stop panicking. Nothing will happen to you. Those worms were dead. They were just uncurling because of the heat. For future reference -- it's better to defrost fish in the fridge for 24 hours. The faster you defrost, the more you damage the fish.

Cheers,
-Helen

Anonymous said...

MY DAY WITH WORMS!
We just cooked up a frozen Alaskan Halibut filet tonight that my husband caught last fall. I spotted a worm exactly like you speak of - 1 in. long, very thin, and either white or pinkish. I found 4 coiled up in the cooked meat. Needless to say, we didn't want to eat it. Are there any EGGS in the fish from the worms?
We have a small goat herd and I was just deworming them and studying up on the goat worms (totally different of course), and had spent the whole day cleaning pens and feed pans and water pails to stop re-infection to my goats. THEN, I come inside to eat fish and found WORMS in my fish! I'm sick of dealing with worms today!
ARGH!
Julie

Helen said...

no, there can't be eggs. Other people have asked about it. Search the comments of this post for more info.

sorry that you are having such a wormy day :(

Tanya said...

This post is fantastic! Very helpful and upfront. Its nice to hear a foodie talking reasonably about parasites!

Nate said...

I am disappointed that it took my wife finding a cod worm in some cod that I had shipped from Seattle to my home in the high desert (Albuquerque) to discover this awesome blog.

I was trying to prove to my wife that I wasn't a heathen (when I suggested cooking the fish would still be ok), and that the worm was really no big deal. I even told her that I suspected we both had eaten them before in restaurants as I don't recall ever seeing any other dark stringy objects in a cod, pollock, or haddock flake before....

Anyhow, I found your blog for that reason, but now I'm reading it a lot for the recipes and other things that I discovered. My wife still made me throw out the cod though...

Helen said...

Hi Nate,

Sorry about the cod :( I definitely understand the ick factor, but they are indeed completely harmless after the fish is cooked. Unfortunately, these little worms have a tendency to ruin people's appetite.

Cheers,
-Helen

Anonymous said...

aaaaaaahhhh!!!! I've been trying to be better about eating more fish but as I'm originally from Finland, the idea of eating fish that wasn't caught that morning is a bit gross. However, like I said, I've been experimenting with some of the fish I can get in our local Smith's (small town- it's our only grocery store). Today I decided to try the cod, and of course found a gross little wormy in there. As so many others who have commented, I freaked out and called my grocer immaediately and was told that they were normal and safe, etc. I was also told to bring it in if I want for a different piece or a refund. Thank goodness I found your website, so now I can stop gagging (and I actually finished the piece I cooked) and keep the rest of the cod for later cooking. I know someone else asked about the freezing of the "wormy fish", and you said that as long as you cook the fish, it's fine to eat the worms. But I wanted to ask if the freezing really, for sure kills the wrigglers? :) I think I would sleep a little better at night if I knew the little fiends aren't having a party in my freezer.:) Thanks!

Helen said...

yes, freezing fish for 7 days does kill the parasites. but freezing a lean fish, like cod, will totally ruin its texture.

mag said...

Just found one of those dark thin long curled up worms in my very fresh wild sockeye salmon (a real WOW moment as I eat a lot of salmon but never really look at it as I was under the impression that salmon flesh did not host worms, hence I often indulge my passion for salmon sashimi, that is, USED TO, before reading this blog). It was mentioned at the top of this article that only 3 worms are potentially harmful to humans: Pseudoterranova decipiens (a.k.a. “cod worm” or “seal worm”), Anisakis Simplex, and Tapeworm.
I gues the first one is obvious and the last one we have all heard of (thought it came from uncooked meats or unclean water, not fish - SURPRISE). What type of fish harbours tapeworms and what type of fish harbours the Anisakis Simplex>

Helen said...

Hi Mag,

The salmon used for sushi is previously frozen, which kills parasites, and most of the time it's farm-raised salmon, which is way less prone to parasites than the wild coho and sockeye. Anisakis can be found in all types of fish (cod, flounder, etc), tapeworm is most common in the west coast fish like pacific salmon. If you are cooking the fish you don't need to worry about parasites. If you are eating it raw in restaurants, you don't need to worry about it either because it's previously frozen with the exception on species that are not prone to parasites.

Cheers,
-Helen

Anonymous said...

This has been very educational blog. Those vein-looking streaks in fish that I was always wondering about were actually worms!

I went on googling today as I came back from the fishing trip off the west coast of Ireland, and discovered several worms in each of the congers and 'the poor mans cods'. Some of them were loaded with a worm every centimetre of the fillet part of the fish! I did not realize fish can have worms before, and was very puzzled. It did not help to find out that they were harmless, the catch ended up in the bin.

Just wondering about cold smoking the fish. In the cold smoking process the temperatures are lower than 60C, that means that worms may survive. I don't know about US, but in some parts of the world cold smoked fish is very popular. Is cold smoked fish unsafe?

Martyn

Helen said...

Hi Martyn,

Not all the veins are worms. Fish do have visible veins too :) But if it moves, it's a worm.

There are move safety issues with cold smoking than with cooking fish. The salinity of the brine might kill the worms (but it needs to be salty enough and the fish needs to sit in it long enough). I would not recommend cold smoking at home unless you are using a species not prone to parasites and know what you are doing.

Cheers,
-Helen

Esperanza said...

Hi Helen!! Very useful information, thanks!! I literally just sent my husband back to the supermarket to ask for our money back, as I one of these little worms managed to ruin the scrumptions cod ceviche I was preparing for lunch. I am not squimish at all, but I found it difficult to ignore as it was moving!!!!
The fishmonger said that it was a naturally occuring thing, but I am really looking forward to what you have to say about cured fish...

Thanks!!

Helen said...

Hi Esperanza,

Cod ceviche is not a bad idea. Cod is very prone to parasites and is not intended for eating raw. You should be buying sushi grade fish for ceviche. Curing doesn't kill parasites. Try scallop ceviche sometimes. Scallops are not prone to the parasites that can live in humans, so they are a much safer bet. Branzino (Mediterranean bass) would also make good ceviche. Given that it's farm-raised and fresh enough to eat raw. If you want to learn to make ceviche at home safely, here are some tips on working with raw fish.

Cheers,
-Helen

Three of Cups said...

oh man. me and my dad went fishing today and had a giant cod on the line. 'cooked' it (it wasnt very hot...we wanted it hotter, but House was starting, so, yknow....)
digging into my dinner, and suddenly i realise its MOVING. There were loads of worms in there. Like, at least four. and hopefully none of them made it in to my stomach without me realising it. I've just spend ten minutes trying to make myself sick and fear I may never eat my favourite fish. I'll let you know what the effects of ingesting a live one are if I experience any.....ugh!

Helen said...

Poor Three of Cups,

So sorry that your dinner was ruined, particularly a dinner you caught yourself. I hope you don't get sick.

Cheers,
-Helen

Alan said...

Hi,

I have a couple of questions as I just found worms is a piece of fresh sockeye that I purchased. Only I found them after I started eating it as sashimi. Apparently I had cut a few of them up and they were writhing away. I tossed the rest of the salmon out but worried that friends as well as myself may have also taken a piece of raw wormy fish dipped it in soy sauce and wasabi and consumed live worms right off the cutting board so to speak. Are they like tapeworms? If you cut them do they reproduce in you? Is there any danger of Trichinosis? Will pieces of the worm be contagious and spread?
This worm was white and very thin and round kind of like mono filament line. It had to be less then a millimeter thick but several centimeters long like a whip worm.

Helen said...

Hi Alan,

Sockeye is very parasite prone, so consuming it raw is a very bad idea. What you saw was most likely a cod worm and if you are not experiencing any symptoms from it (severe stomach ache, etc), those little guys probably didn't cause any harm. However, there is no guarantee that your salmon did not also have tapeworm and the symptoms from it might not manifest themselves for a long time. So, I suggest you go see a doctor and ask for advice.

Cheers,
-Helen

Anonymous said...

Yesterday I had the wonderful experience of finding a long (as in about 4 inches long) string-like worm in my Sockeye salmon... Major yuck! After removing said worm, I cooked the fish hard and partook anyway, but my question is about the worm's EGGS... can they survive heat? What about stomach acids??? You always hear those stories about the the vast numbers and tininess of tapeworm eggs; so what about these guys???

Helen said...

Neither the worms, no the eggs can survive in 140F temperatures, which is when the fish is done. But the parasites are not in the egg form in fish. They need a mammal host for that.

Anonymous said...

My wife just found one of these in her cod from Whole Foods. We both got grossed out and went straight to "the google" and found your blog. Thanks for the entry and reassuring us we'll live through the night and not be consumed from the inside-out.

chestr said...

thanks! just bought a few pieces of fluke in the farmers market, fresh, good... until i saw a worm before i started preparing the meal. i was going to throw it out, but since it had been frozen for a few days, I{m going to cook it and then eat it.
agh. hate worms though.
nice blog.

Anonymous said...

We just found a ton of coiled up little worms buried in cod that we bought from a store in chinatown. The tail of the fish had some red spots and areas of irriation -- I guess we should have paid more attention to this before buying this cod....

Vix said...

Well, well, well... I find it fascinating that someone is passionate enough to write about this sorta stuff. Very interesting blog... you know I had no clue there was such thing as worms in fish flesh - yuk. Good that they're not like, fatal or anything. Would you happen to know anything about blood fluke in tuna?

pekmez said...

Thank you! This was a much more reassuring find than a youtube video of a cod worm in a costco fillet. Yes, a video. Which means, of course, that there was a reason for it to be a video. Ew.

I found 2 cod worms in a whole cod today - this must be my 8th or 9th whole cod of the season from our fish CSA, and the first time I've found any worms. Of course, today would be the day I'm not cooking immediately - this cod was planned to turn into salt cod / baccala.

So obviously the two worms I found are no more, and I did rinse and inspect (but didn't try the candle test). Now the filets are salted in cheesecloth in my fridge. They will be fully cooked before eating - but if I missed any worms are they going to stay alive and coiled up in my salt cod for the next month and a half?

Helen said...

a salt cod (at least the traditional one) requires so much salt, that it will kill the worms. At least that's my best guess :)

Cheers,
-Helen

Anonymous said...

Thanks so much for your informative post on fish parasites -- specifically cod worm. I love fish and cook it frequently, so it's hard to believe I never ran into one... until tonight! I'm a real stickler for food hygiene, and was about to chuck tonight's dinner in the bin, but your post, and others' comments (thx for the link to photos as well), gave me the courage to cook and eat our fish tacos as planned. I'll certainly be back to read more (hopefully on more appetizing topics) in the future!

Anonymous said...

being from a Tropical Island that depends a LOT on seafood and fish for protein in our diets I have to say that I have come across cod worms. I was freaked out and disgusted and needless to say, ready to throw the fish out. My father, however, explained that this is a natural phenomenon and made me boil the dried cod a little longer than usual to ensure that the parasites were gone...

Drew said...

While the material is somewhat dated - blog started in 2006 & now 2010, it's an exceptionally well handled topic. I was grossed out at the grocery store when I saw them and woman behind the counter just said don't worry most fish has worms, you just don't see them. I think had I not found your blog and this topic, I'd be in for a fight everytime I tried to suggest fish wo my wofe. Being a fish lover, I can only say the one thing Thanks.......Thank You!!!

Anonymous said...

guess. I bought cod from whole foods about 2 months ago and it was in my freezer. I kept it for an emergency. Today when I opened the package . I found a yellow/pink worm about 2 inch long. I thought it was some fibre only to realize it was a worm . I threw it in the trash and came right here on google to find out what it was when icame across this blog. Imagine if I found it alive .. I would be still freaking.

lazalzera said...

I love cod fish. I've been eating it for quite sometime. I eat it almost every week, and then about a month ago...the unthinkable. OMG! I found a long worm while marinating it...ewww! So I became brave, took it out, grilled it really well and then ate it...oh God! I called the supermarket and the seafood guy said it was harmless and very common. BUT...my love for cod had been shattered. So, I bought it fresh again yesterday. I looked at it throughly while marinating it and saw nothing...great! I grilled again in foil with butter, salt, pepper, lemon, and dill...hmm so good right? As I was serving some and separating some layers, I saw not one but at least three freaking dead worms all curled up...ugh! NOOOO! Now, I can't stop thinking about how many worms have I eaten without even knowing it, and also feeding it to my girls and hubby. So today, I finally did some research and landed on this blog. Thank you for all the information. However, I can't take away the image in my brain of those worms. What do I do? I'm also concerned with mercury, so I buy cod for that reason...low in mercury. Any other suggestions since you have done so much research? Thank you!

Helen said...

Sorry about your worm experience. There are tons of fish that are not prone to worms at all: anything farm-raised and tuna. Anything besides large tunas (yellowfin, big-eye, and bluefin), swordfish, tilefish, and king mackerel is low enough in mercury not to pose concerns unless you eat it for breakfast, lunch and dinner every day. Look in the left column of my blog. There is an article there on mercury. It's really not as scary as media makes it.

nwboardgrl said...

yikes...my boyfriend and I have started buying fish from this awesome fresh seafood store, and got some cod today. I opened it up to make fish and chips, and found not one, but TWO worms. The first one looked like a tiny rubberband, so I set it aside. It started moving. EW. Ok, the thing wasn't but maybe half an inch long, but I am not a fan of anything bug-wise besides maybe a ladybug or butterfly. Haha. The second one was mostly clear with a greenish tint, and he was in it partially. My skin is crawling even now. Sooo, I asked my boyfriend about it, and he didn't know if it was harmful. I called the seafood place and he said not to worry. I cooked the hell out of the fish, but it was tasty. Just hope I don't have anything making a new home in me. YUCK!!!

lazalzera said...

Dear Helen,

Thank you for replying right away to my recently experience with parasites in my beloved cod, and also for your post on mercury. So I went by Whole Foods Market and spoke to the fish dept employee. Based on the preferences I gave her: parasite free, fresh, wild caught, and low in mercury, she advised on a fish called "corvina". She said that the fish that hang around closer to the bottom of the sea are the ones more prone to parasites. Anyway, so I cooked the corvina today in a mix of olive and grape seed oil, and it turned out great. The down side was the smell inside my house. Next time I think I'll experiment with it on the grill. Your thoughts and advice are greatly appreciated. Thanks!

Helen said...

I've never seen convina in our area fish markets (in Boston). I am so glad you found a fish you can eat.

Anonymous said...

I found your parasite post because, tonight I was completely revolted by finding a cod worm in the cod I was ready to prepare. I screamed, wrapped it back up and threw it away. It was just as you described, the size of a white and pink string that MOVED! I proceeded to cook the other blue fish and will never buy fish at Giant again. We ate cod last night and I had another piece to cook. I typed in cod worm and by coincidence, that's what it is called and it is harmful. I'm so glad to be able to read this and beware. I've never heard of fish parasites, but now I'm informed, but still stressed about having had to see it and deal with it. I'm taking it back to Giant and hope they clean up their act.

Helen said...

Hi there,

Please read the blog post carefully. Cod worm is NOT harmful when cooked. It's not your fishmonger's fault. They don't need to "clean up their act." These parasites are part of nature and there is nothing your fishmonger can do about them. If you are revolted, I totally understand.

Cheers,
-Helen

David said...

I worked 3 months in a processing plant . Inspecting for parasites was NEVER done. Trust me they are the least of your problems.
That was 15 years ago to this day I cant bring myself to eat any fish I didn't catch myself.

Anonymous said...

Hi, I am changing the subject from fish parasite to clam parasite. I went clamming in a clean bay and 99% of the the 70-some clams I caught were infested with a round worm in their GI tract. Fortunately I used them as clam chowder and steamed and cleaned them before I put them in the chowder. My question is what would happen if I ate one of these clams raw including the parasite?

Helen said...

I don't know much about clam parasites, but my best guess is that eating them raw wouldn't be a good idea.

Anonymous said...

I found one in a cod fillet from Whole Foods. I had already cooked it. Couldn't eat the rest. Gave it to my wife who didn't believe it was a worm.

Anonymous said...

Hi my name is Catherine I knwo these is an old blog . I live in Norway and yesterday I bougth some fresh monk fisk fillets after I marinated them and when I was paintint them with oil It came out a couple of red worms of around 3 cm long. I tryed to dont do a big deal of it so I took them away and grilled the fisk I think well. It was delicious but how I have a 2 years old boy who also ate and I breast feed a 5 months baby I preffer to be totally sure they aren't dangerous. I readed different information about fish parasities and I tought monkfish has mostly some white or soft pink worms anasakis... but this were red? can you please tell me what kind could it be? are they dangerous? Thank you but mothers can never be to carefull.

Helen said...

Hi Catherine,

Cod worm and anisakis can be of all different colors including red. They are very common in monkfish and are not dangerous at all if you cooked the fish. Even if you were to eat it raw and even if one of them were to survive and make it to your stomach, and even if you were to get sick, there is no way it can effect the baby your are nursing. If you cooked the fish, I would stop worrying :) Unlike tapeworm that can go unnoticed for months, cod worm and anisakis will give you symptoms pretty quickly. If you feel fine, it's all good.

If it makes you feel any better, I give my 3 year old daughter cooked fish that had worms. I try to remove them all, of course, because they are yucky looking, but it's not a health hazard.

Cheers,
-Helen

Anonymous said...

Thanks a lot Helen. I can relax now. We are feeling fine so I guess i grilled well. Thanks again. Catherine :)

Anonymous said...

Hi Helen I came here after googling white worms in fish. Thank you for the info. This morning I was cleaning up from last nights dinner, and in the bowl I had below the strainer that held the fish that I had rinsed before cooking last night, I saw a white little suspicious little worm. It was still alive and totally grossed me out. I cooked the fish really well and didn't notice any while I was eating thank GOD but it has changed my mind about eating cod in the future. thanks for the info!!!K

Anonymous said...

Phew! I found a dead worm in some cooked (to opaque) white fish. Googling brought up your blog. I kind of expected the answer I saw, but it is reassuring to see it.

Congratulations on your high Google ranking for "i found a worm in my fish."

Anonymous said...

so i had haddock on friday. today i notice white specs in my stool. after some sleuthing it would appear that i have one of these parasites breading in me..... what is the urgency of medical care here?

Helen said...

Hi there,

I am not a doctor, so I can't give you any medical advice. Contact your doctor and see what he/she says. Would you mind reporting back once they do necessary tests. I'd be very surprised to hear that you were infected with parasites assuming your haddock was cooked.

Cheers,
-Helen

Reina said...

Wow I have never seen an active thread stay open for so long! Thank you for replying to so many people and for the informative article! Today was my first encounter with a cod worm today, I brushed off something from my finger thinking it was a piece of rolled paper towel at the sink today after handling partially frozen cod from Costco. I freaked out, I panicked; my little sisters thought I was bitten by the way I was screaming. I freaked out even more when I saw that it was wriggling. All of this because I watched, "Monsters Inside Me" on Animal Planet about worms that live in fish stomachs. I new most fish carried them but I had no idea it could be in their flesh. I'm still reeling from the experience but I feel more assured after reading your article that this is more common than I once thought. I also enjoyed reading other people's firsts. I am a natural fish lover, I loooove fish but to think I used to eat raw pieces of halibut from Costco...ugh! I'll definitely be more cautious from now on. :)

Donna said...

Hi

Thank you for such good quality information. Like so many other people who have written here I had no idea these worms existed until I found some last night in some cod I was preparing. I bought it from a supermarket fishmonger, my mum bought and cooked the same and telephoned me to warn me how many bones she'd found. As I was giving it to my young son I paid very close attention to the flesh, looking for bones. I was appalled to find worms wriggling in the flesh,3 in total. I did not use the fish but I decided to try to find out what they were and came across your blog.
Thank you, I now know what fish to look for in future and I will certainly know not to panic if I find them again.

Anonymous said...

I found a cod worm (wiggling still) in the cod I purchased from Costco located in South San Francisco. I couldn't eat the cod (or the worm) so I returned the fish to Costco. It is interesting to know that they are rather common. I won't be buying any more cod.

Anonymous said...

Just found a cod worm in my cod from a very reputable Asian market outside of Chicago. Freaked out until I saw your post. Still won't eat the fish though...thanks for the info.

Doug Packer said...

Very interesting. If the cod has been frozen - I know you said not to freeze lean fish, does this definitely kill the worms and parasites. My wife and I hate fish too cooked. We like it when the fish has just changed from translucent to milky colour and not yet solid and white. The flesh falls into segments. We've no idea how hot it is but it's cooked less than 5 minutes or steamed. So if it's frozen first are they DEFO DEAD? Thanks for great articles - Doug

Helen said...

yes, freezing will definitely kill parasites.

Anonymous said...

Hi all
and thanks Helen for all the info :)
i like to know where the fish worms live in the fish i mean does it live in the body or the stomach? and what about the Salmon

thanks alot

Q

Jason said...

they start in the stomach, but can get into the flesh.

Anonymous said...

Thanks for this!

EMR said...

Good that this blog caught me attentive and I now know all about it.Good to be exchanging ideas and learning about new ailments.

Trice said...

I notice you only said three were harmful what about fish flukes

Helen said...

I was reading about trematoda (fish flukes) on wikipedia and it sounds like they are not common to the fish types used for sushi. I'll need to do more reading to give you a better answer, but that wikipedia article will probably give you lots of good links.

kathy said...

Thank you for this excellent info! I am sitting here googling "worm in fish", because I just found a perfect specimen in my cod that was supposed to become fish tacos. I believe you about the worms not affecting the fish quality, but I'm pretty squeamish when it comes to cooking fish anyway. So - the fish, and the worm, are incarcerated in a bag in the freezer where I tossed them in a freaked out frenzy ... and they will stay there. I'm having french fries for dinner, dipped in the cilantro sauce that was meant for the tacos!

Chef said...

You rock! I'm a classically trained chef and had no clue about cod worms (we were taught only monk fish was wormy). I don't eat much seafood so I thought I never encountered any, but then I remembered while filleting salmon at work I used to wonder why they were so "stringy"... I just got chills! Thank you for such a vivid informative blog.

Anonymous said...

Hi,
I was cooking two lbs of salmon today... while marinating them in a soy sauce/brown sugar i noticed a clear little worm on top of the salmon skin. I moved the marinating tray a little bit and it disappeared and I couldn't find it again. This is pacific wild salmon that I got. I am just wondering if I found a worm again how do I kill it??? Since I couldn't find the worm I just cooked the fish and tried to be careful while eating the fish... (I really didn't want to waste the fish) I baked the fish at 375 for 22 minutes about... hopefully taht Killed IT??

Helen said...

The only way to guarantee that you killed it is to cook it to 140F (check with a thermometer). You can cook to about 130F and it will finish off with residual heat while resting. Cooking to lower temp will weaken the worms and they will be unlikely to cause any harm, so don't panic :)

Unfortunately, salmon cooked to such high temp is not very tasty. I like mine at about 120F. But it's a risk, just like down hill skiing (actually down hill skiing is probably more dangerous).

Cheers,
-Helen

Anonymous said...

Hi,
Thanks for your prompt reply! You are so helpful! This is actually the third time I am typing the same comment for I forgot to choose "anonymous" instead of "google account" (I don't have a google account) and I kept losing the comment I typed up. Hopefully you don't get three comments by me with the same content but different versions. :x
So actually I was wondering what to do with a "live" worm before cooking. So let's say I spot a worm on a fish, I remove it with my hand (if using my hand is okay, or are chopsticks better??), then what do I do with it?? should Ikill it before throwing it away in the garbage? If so, then how do I kill it before cooking the fish??
THank you and hopefully this comment goes through...
Evelyn

Helen said...

You don't have to kill the worm (unless you want to). Just take it out with your hand (or something else if you are squeamish) and put it in the trash can. It's not like that worm will start breeding in their and taking over your house :) They are really quite harmless unless swallowed whole and live.

Cheers,
-Helen

Anonymous said...

I found a worm in my reheated cod today - I had BAKED it, then BROILED it the night before, and then microwaved it the next day and the worm was still alive!!! I have it in a plastic baggie right now and it is slithering all around - ick!! I am pregnant so am heading off to get treated for parasites - this is ridiculous!

Anonymous said...

I find this information very useful. Yes, I will continue to eat cooked fish. However for it as being raw, no way!!!.

Anonymous said...

Thank you for your informative article, however I have become increasingly disappointed that almost every time I purchase flounder from Whole Foods, it has worms in it (notice your fish was also purchased at WF). For such and expensive "supermarket" they should be using better fish mongers and take better care to offer higher quality products to their customers. Thought I would share so people can be aware of purchasing fish at WF.

Helen said...

flounder is packed with worms no matter where you purchase it. if it was previously frozen, the worms won't move and you won't notice, but if the flounder is fresh, it's hard for them to get all the worms out no matter how hard they try.

Rubens said...

Hi There, seems to be a joke, I,ve never eaten a worm in any fish , Living in USA for more than ten years I knew what quality control means. Do you really think it´s nice find a parasite in a fish when you eat it.? Please. thanks

Anonymous said...

I recently dug up some nice fat butter clams in Washington and was all excited about clam dinner but when I opened one up I found it's soft meat riddled with worms. I found this article while google searching what they might be. Have you any ideas what kinds of worms penetrate clams? The clams seem other wise healthy ... at least for a while.

Helen said...

I have no idea what kind of worms penetrate clams, but you don't want to eat those clams raw! If you are cooking them, the worms should be dead by the time you eat, but the clams might not be very appetizing ;)

Anonymous said...

hi there.
last week prepared bagels with cream cheese, smoked salmon and lots of black pepper and lemon[this is relevant, to set the scene]
my son and i had eaten 2 halves of bagel each when he noticed tiny worms wriggling away on the salmon partially hidden by pepper etc. it was Wild Alaskan salmon. enviromental health have taken the `samples` and im waiting to hear what type of worm they are. they were about 1cm long and pale grey. are there any benign salmon worms because odds are we ate some!!

Helen said...

Hi Anonymous,

You should probably see a doctor if you are worried. I can't offer any medical advice, but keep in mind that even if you consumed a harmful worm it might pass through you with no symptoms of harm. So this might not be the end of the world :) Call your doctor and see what they suggest.

Cheers,
-Helen

Anonymous said...

i liked the article and will still look for more of you, i am not really particular with fish but its included in my line of work, although not much, but right now important. My keeper saw some round worms in the Indian mackerel that they are going to feed to the seals. i have not investigated it myself and right now busy gathering info on the subject before i proceed. By the way, the macs are thawed before it will be fed, i will try to see info on the effect of deep frozen fish on parasites. I am a little bit rusty in parasitology right now...but i love cooking fish. from riyadh

Helen said...

most parasites will either die or at least get significantly weakened by freezing. if the fish was frozen, there is not much to worry about.

Anonymous said...

Hi there, My friends and I made sushi the other night. I usually only have veggie sushi but my friend brought Salmon and put it in a couple of rolls. I assumed she knew what she was doing, but now I'm reading about all the risks and I'm worried..especially about tapeworm! I don't know what kind of salmon it was or whether it was previously frozen. What is the likelihood of getting tapeworm from eating 2 or 3 pieces of sushi? Do you know if there's anything I can do at this point to get it out of my system?
Thank you!!!

Helen said...

please don't panic pre-maturely! The likelyhood of you getting sick is probably smaller than the likelyhood of you getting injured while driving :) I am not a doctor and can't give medical advice. If you are that worried, call your doctor.

Anonymous said...

Thank you! I almost threw out my very fresh and yummy looking cod filet and now I'm going to live on the edge, cook it, and consume it.

The fish, not the worm. :)

Anonymous said...

BROUGHT HOME FRESH COD FROM MY "CLUB" STORE TODAY. THE LAST PIECE WENT INTO THE PAN AND I TURNED TO FINISH DINNER. WHEN I CAME BACK TO THE STOVE, THERE WAS A TINY HAIR SIZED WORM SWAYING LIKE A COBRA IN A RATTAN BASKET. I REMOVED IT WITH TWEEZERS AND FOUND THIS SITE. IF I ATE ONE, IT WAS WELL DONE. AND THE LITTLE "CHARMER" WILL SOON BE FLUSHED OUT TO SEA!

Anonymous said...

Helen! I am really scared! I was in the middle of eating cod when I paused with my fork in the air (rude, I know) while talking to my fiance and...noticed my fork was moving. It was a white/pink tiny little worm. It looked exactly like a fish bone except it was moving. I had never heard of this happening before in my life and instantly threw up. My fiance thoughtfully destroyed all evidence of the fish while I was in the bathroom so I didn't get to investigate and see if "it" was round or if there were more etc. Now, I don't know if I actually ate a live worm or not but how did it live through cooking? It was in the thicker part of the filet. All the posts I have read are related to eating a DEAD/COOKED worm. This one was CLEARLY still alive. If I did eat a live worm, is there any chance that the time spent in the pan at least damaged it/made it weak? I'm going to be sick again!

Helen said...

Please don't panic. Cooking does weaken them tremendously (even if it doesn't kill them). If you feel fine, then don't worry about it. But I am not a doctor, so I can't give any medical advice. Call your doctor and ask what's the best course of action. Chances are it's nothing to worry about :) I realize the ick factor though.

Jackie said...

I bought Corvina fillets from Costco today and planned on cooking them for dinner. After reading this blog I am not looking forward to opening the package and checking for worms. It is a thick piece of fish so if I don't find any worms, I will cook the heck out of it to be sure.

Helen Rennie said...

Jackie,

Please enjoy your corvina and don't cook the heck out of it. I eat fish 3 times a week and have been doing that for at least 10 years. I don't cook the heck out of anything, even cod :)

Cheers,
-Helen

Janis said...

I was just about to cook my cod tonight and found a worm in it. I am glad to know they are not harmful (if cooked) I went straight to Whole Foods and returned it... I am reading this after the fact. lol, but thank you! You made me feel much better! Don't know if I will ever be able to cook cod though.

Anonymous said...

Dear Helen,

Thank you for a truly informative post about parasites in fish. Do you know if shrimp, lobster, crab, and scallops contain worms in their meat? After an exhaustive internet search, I couldn't find anything. Thanks in advance!

Helen Rennie said...

Scallops are safe as far as I know. It's very common to use them for raw dishes. Don't know about lobster and crab. In Japan, raw lobster is very common, but don't know about parasites. Raw shrimp is not a good idea. In Japan, it is eaten raw, but shrimp is very perishable and has be eaten shortly after it's out of the water. I believe there is also a parasite problem. Shrimp are the way parasites get into fish in the first place. I think they are in a different stage of their development, so they won't look like worms. To make a long story short. Eat raw scallops. Don't eat raw lobster, shrimp, and crab unless your source assures you that they are safe.

Cheers,
-Helen

Anonymous said...

Found a LIVE Parasite in my COOKED salmon!! It was frozen, then baked, then zapped in microwave and still lived and I almost ate it but saw it wriggling on my forkful of fish! So, yes they can survive through freezing and cooking. I looked it up and it is called a Sealworm, which is a parasite. If you accidentally eat one while they are alive, is when you get problems. Called the doctor and have to basically get dewormed, because I would rather be safe than sorry, and dont know how many I might have ate or maybe that was the only one...so disgusting!!! I never knew there were worms/parasites in fish. I wonder how many people a year get sick and think its something else, when really its because they ingested a live parasite from their fish. My eyes are opened! We are told to wash fruits and vegetables because of ecoli and pesticides possibly being on them...but noone knows about Parasites and worms in fish!!!

Anonymous said...

Should have read that before I threw dinner out!!!I used to have an eating disorter so I pick at my food still .Just fried up some cod and found WORMS. Told my husband Stop dont touch that fish His had them in it also.Thanks for writing this so I can sleep tonight ha ha ha

Anonymous said...

I understand my dad cooked cod for my mom for a romantic valentines day dinner that eventually devolved into some sort of biology class with my mom being grossed out, me squealing like a little two year old girl, and my dad dissecting the fish to find all the worms.

Anthony Burdge Jessica Burke said...

Thanks for this. I thought I was bonkers when I was inspecting some monkfish-- bought it yesterday, it had been frozen, thawed & was going to be broiled-- when I spotted several creepies crawling and I thought: it can't be worms. They wouldn't survive the freezing & thawing, right? Wrong. I pulled 'em out and they were still creeping. I had the heebie jeebies & had hubby return the fillets to the fishmonger. It will be a very long time before I have fish, especially sushi. Informative article. Thanks!!!

Anonymous said...

amazing blog....after preparing a number of flatfish for restaurant
use, the "frames" began to "grow" worms. learned that fish 10 miles off shore less likely to have worms.
learned that raw fish with the "seeds" or cysts, an unborn worm , is what kills people in japan,from eating a lot of raw fish.eveeat fish meal.n if not health hazzard, it cuts down your zest for a great fish meal.
Chef Sally

Helen Rennie said...

"kills people in Japan"? I've never heard about worms killing anyone. can you provide a source for that?

Josh said...

How long does it take to get symptoms? Made ceviche and notice a live worm. Who knows if I ate one before a caught it. If suspected I may have eaten one, should I go to doctor or wait?

Helen Rennie said...

Josh,

I am not a doctor, so I can't give you medical advice. I'd call your doctor and ask. I do know that eating a worm (even a live one) does not necessarily mean you'll get sick. But there is a chance.

Cheers,
-Helen

Anonymous said...

A search on google brought me here after having already read some info on various fish and worms.

I'm done with fish. Don't care if they die and are harmless after cooking. I hope people keep complaining. Food costs entirely too much (For most people) for this to be taken lightly. If we say it's okay to find worms, we'll eat it anyway, the industries become comfortable and where does it end? Doctors won't care--cha-ching--money in their pockets from people running to the doctor.

With the increasing consumer demand for fish I expect this to only get worse. Supply, demand means the inspection process is going to suffer.

Personally I'm torn between ignorance being bliss and needing to be informed about what goes in my mouth.

I've been a gardener for many years and still squeamish about some things but this-- is crazy.

I'm slowly moving toward the path of becoming vegan anyway. The food industry is a great disappointment on every level.

There is no way it can possibly keep up with the encroaching pestilence we are experiencing today and to stay profitable, will turn a deaf ear. Thank you for such an informed article and the comments are priceless.

Helen Rennie said...

If that's your conclusion from my article, I've obviously done a bad job. This is not a "big bad industry" problem. It's not a problem at all. It's just that we are so far removed from our food that worms and bugs that are a natural part of the ecosystem freak us out. Doctors don't care not because they'll make more money, but because the cod worm is way less harmful than a tick (not even comparable in the order of magnitude). Hiking is way more dangerous than eating fish, so is driving. Yes, worms are icky, but so are boys when you are in third grade (at least if you are a girl :)

Anonymous said...

have you ever ordered fish (like tilapia) and saw a long white stringy stuff from the fish - is it the nervous membrane or fecal string or a parasite (worm), what is it?

Helen Rennie said...

tilapia is farm-raised, so whatever you saw is almost certainly not a parasite. It's part of the fish anatomy.

Anonymous said...

One person's worm is another's protein!

Garry Reid said...

A friend recently caught a sockeye salmon that had much lighter coloured flesh than he has seen in a sockeye salmon - normally it is very red flesh. Could there be anything bad about this fish?

Helen Rennie said...

As far as I am aware, the color of the flesh is not an indication of quality and has absolutely nothing to do with parasites. It simply depends on the diet. There is such a thing as "white" salmon whose flesh is gray beige.

That being said, sockeye salmon is very prone to parasites, so I would strongly discourage you from searing it raw or semi-raw unless you plan to freeze it for 7 days.

Anonymous said...

I found your site after I found a live worm in a piece of cod which a restaurant had prepared for my lunch in Oct 2013. I'm still not really comfortable with fish since and tend to think I am finding more and more.
Especially in fish like sea bass, bream and sole... when I lift the top filler of the cooked fish away and then peel the spine bones off I usually see long thin black 'threads' which are no thicker than a human hair, but I'm pretty convinced they are worms so I scrape them all away.
If you know what these are, I'd appreciate you letting me know if they are veins or something other than worms.
I also have a great pic of a worm I found in the same restaurant about 6 months later - I'd love to send it to you as its probably the fattest wormiest worm you ever saw in a fish. I do not go to that restaurant any more...!!

Helen Rennie said...

little black lines are veins, not worms. The long stings you find near the back bone are veins too.