Sunday, October 8, 2006

Questions about cod worms

Before I introduce you to more fish parasites, let me answer all the questions I got about cod worms.

Q: How do you remove cod worms? Do you have to use a match like you would for a tick to ensure that no part of it remains in the fish?
A: No match. They’re only potentially harmful if you ingest them live. I just pull them out with my fingers (wearing gloves since I am a squeamish wimp), but as Stephanie suggested, tweezers might be an easier way to remove the worms.

Q: What would happen if a cod worm were to survive in your stomach?
A: Nothing life threatening or permanently damaging will happen, but you are likely to experience a terrible stomach ache, nausea, and vomiting. If you experience these symptoms after eating raw fish, it’s important to tell the doctor which species of fish you’ve recently eaten raw, cured, or salted. In US, the instances of parasite infections (anisakiasis) are so rare that they are often misdiagnosed as appendicitis, ulcer, or some other gastrointestinal disease. If diagnosed correctly, anisakiasis can pass all by itself (when the parasites die), or be treated with a drug called albendazole. In rare cases, surgical intervention might be necessary.

Q: I found a worm in tuna at a sushi restaurant. What do I do?
A: What you probably found wasn’t a worm, but rather a strand of fat or sinuous tissue. Worms in large tuna (such as yellowfin, bluefin, and big-eye) are exceedingly rare. Even if what you found was really a worm, don’t worry. All restaurants in the U.S. are required to freeze fish before it is served raw. The freezing process will kill any worms that aren’t removed via inspection. However, if that “strand of fat” was really moving and wriggling on its own, then it’s not a strand of fat---it’s a live worm. One possibility is that the sushi restaurant served you a small tuna (such as Bonito), which is susceptible to worms. Most fresh fish sold as “tuna” is large tuna. As an extra precaution, you can ask your fishmonger or sushi restaurant the tuna species. If it’s yellowfin/ahi, bluefin or big-eye, then you shouldn’t need to worry about worms/parasites.

Q: Is eating fresh, raw yellowfin, bluefin or big-eye tuna dangerous?
A: No---at least, not as far as parasites are concerned. Your chances of dying in a car accident driving to/from your fish market to buy a loin of tuna are much higher than your chances of getting sick from a parasite from the tuna you buy. Parasites are virtually nonexistent in tuna meat sold fresh in the U.S. A more important concern is bacteria. Fish meat is more susceptible to bacteria growth than other types of meat (e.g. cow, pig, duck). So, it’s important that you buy from a reputable source and keep your tuna on ice at all time before serving (I bring a cooler with ice-packs with me to the market).

30 comments:

sam said...

finding a codworm in my fish'n'chips when I was young guaranteed that the rest of my childhood was spent eating plaice and chips instead of cod and chips.

Helen said...

Oh poor Sam! That must have been awful. I found a worm in cooked califlower when I was young, and it took me several years to start eating it again. I haven't seen plaice in Boston area. Is it a white fish similar to cod? Is it common in England?

Sarah said...

When my daughter notices a codworm on her fish n chips, she got paraniod on anything with fish. I can't blame her right? hehe.

Helen said...

Hi Sarah,

Finding a worm in your food is extremely unpleasant and I can relate to your daughter staying away from fish because of that. If she is really disgusted with cod worms, here are some fish she can still eat without worring about them: salmon, trout, bluefish, red snapper, striped bass, mediterranean bass (branzino), sea bream (orata), mackerel, sable. As long as she avoids white fleshed fish, the odds of seeing a cod worm are close to zero. This isn't to say there couldn't be other parasites, but they are not likely to be visible and ikky looking.

Cheers,
-Helen

Helen said...

oh, and tuna of course!

Pete -Rugby, UK said...

I just found a horrible worm in my cod and chips and hence why I'm here. I've been retching for about half an hour and the slightest thought and im off again! Never knew anything existed in our food chain, i know one thing for sure and that is I'm gonna go for place next time **retch**
In fact, I've gone off take-out quite a bit since I found a pube in my curry. **double retch**

Anonymous said...

I just found a worm in some cod I was cooking to make baby food..don't think my little one will be having fish just yet !

jpsquirrel said...

I really appreciate your article on parasites and specifically the pictures which enabled me to identify the two worms I found in my cod fillet as cod worms. I was feeding myself and my 15 month old daughter the fillet, and had just finished telling my 4 year old son that he would sit at the table all night if he did not at least choose to taste my fish dish. This was my third time cooking fish, first time cooking cod. I prepared it my rolling in seasoned flour, egg with lemon juice dip, rolled in breadcrumbs and finally melted butter before baking at 350 deg for 20 mins. I was so freaked out, I lost my appetite even for the vegetables I prepared. Please understand that I just recovered from 3 days of intestinal virus with cramping, etc. The first website I found on fish parasites was a naturopathy site which reallly had the fear factor working (I suppose to sell products). Thanks again!

Anonymous said...

It might be helpful if you can put up some photos of common types of worms found in fish.

Anonymous said...

Is there a possibility that the fish is infested with parasite's larvae which do not look like a worm or too small to be visible?
Then there's a risk that we will consume infested fish without knowing it.

And whether is it possible for the parasite to gnaw through and live inside human tissue? those parasites live inside the flesh of a fish and can they do the same when they reach our stomach alive?

by the way, you should delete the comment posted by anonymous guy at 10:58 AM.

Helen said...

From what I understand, the parasites can't be in larvae state in fish, but they can definitely be small enough to not be detected by an untrained eye. That's why you should choose the fish you eat raw wisely. If you are cooking the fish, none of this matters because the heat will kill the parasites.

Anonymous said...

Just from the fish biology point of view: any fish like tuna that spend its entire life preying at mid depth of open ocean or sea should be considered free or almost free of worm-like parasites.

Brittney said...

I cooked cod fillets for the first time ever tonight, and happened to find a worm in my piece halfway through my meal. It certainly grossed me out, but I thoroughly appreciated the comment regarding other creatures. It makes a lot of sense that other creatures would gladly have consumed my piece of cod, and what makes us think we are above finding a worm in our fish? Thank you... because of these articles, I will continue to eat fish.

Question said...

First off thank you, thank you, thank you so much for your blog. I was looking to make a sea food stew and needed a list of dense flesh fish to choose from.
Gee, I'm guessing I am just lucky because I've not seen the worms yet but to be honest I never eat raw fish and I tend to keep my frig a bit colder then most people do. Not to mention I love plaice so it was a real treat for me when I lived in England so I never did eat cod and frankly as a fish I don't care for it.

Anonymous said...

I have found worms in the meat of the following wild caught fish in Maryland. Largemouth/smallmouth Bass, Blue gills, crappy, and yellow perch, I have no idea what these worms are so when I find one the whole fish goes in the trash can. The worm looks like a small twisted up pile of red colored string. They also seem to have a small hook shape to one end. The worm also seems to have a hard segmented outer shell.

Helen said...

those are probably cod worm. but no matter what these worms are they are harmless once the fish is cooked.

daybreak said...

It was so nice to finally information on this presented in a clear and non-biased format.

Uffe Hellum said...

Helen, Sam: Isn't English "sole" the same as American "plaice"? Flat, insipid bottom fish, not as good as flounder...

Helen said...

Hi Uffe,

Just looked up plaice on wikipedia. It's the flatfish family like flounder and sole. What we call sole in US is really a flounder. Fish names are so confusing. Every region just calls them whatever they want. The bottom line is that plaice too can have cod worm and anisakis.

Cheers,
-Helen

Anonymous said...

I am truly grossed out here! Too bad I cannot upload some pics of the creepy worm I just found on my cod fillet! I am glad my eyesight still works, otherwise chances are I would not have seen it once the fillet was on my plate! Yuck!!

Anonymous said...

The freezing process that US sushi undergoes is not enough to kill worms - that takes 60hrs at -4F. You're still better off eating sushi at a restaurant; they serve high quality fish.
A 1.25" fillet cooked for 10 minutes in a 350F oven will render any worms perfectly safe.

Walter said...

Hi!First sorry of my english,I learned it just myself.So I am working in Norway,a lot of cod living around here,and codworms too.I really like fishing,and the taste of the cod,but unfortunately they are full with worms,too disguasting for me.Once i've cought a really sick cod,when i cleaned it inside i found a lot of worms,and the lever was green....that was too much for me.Now I would like to know has the coley or sainthe also codworms?Because that is the other kind of fish,what i can catch here.Until now i did'nt find worm in coley,but it is also white fish(a little bit grey actually)so I think they should have also.This blog is great,I learned a lot from it.Thank You!

Helen said...

Hi Walter,

Coley and saithe are very similar to cod and can have worms too.

Cheers,
-Helen

Alex said...

Blech. Found a worm in my fish tonight. It was cod, cooked, and the worm wasn't moving. Was still enough to make me lose my appetite. I think that from now on I'm going to take smaller bites and check a little better when I eat fish.

smokeybaconfact said...

I bought some raw fish and cooked it in the microwave. It was thoroughly cooked, but I found a moving worm in it. I then put the fish back in the microwave for 1 minute. This was begrudgingly as it would mean the fish would be way over cooked, but I wanted to make sure any other little ones hiding in there would be dead too. I couldn't believe it but the worm survived this second cooking! Another 90 seconds - finally dead.

Jeanie said...

I have been eating Cod lately because it is lent. It was so delicious Fri. nite. The Groc. store fried my cod for me & the famliy loved it. The next morning I got on the internet to see what a cod fish looks like. There were numerous comments about the cod worm & it said on U-tube there were pics of the worm. I nearly got sick. I will never eat fish again. It's sad but it is so disgusting.

Helen Rennie said...

Hi Jeanie,

Apples have worms too :) At least they used to until farms started spraying them with chemicals to death. And not all fish has worms. Anything that's farm-raised (salmon, branzino, trout, etc) and tuna are completely worm free.

Cheers,
-Helen

littleblackmarks said...

I pulled a 1" wriggling worm out of my cod fillet last night pre-cooking and must admit I screamed a fair bit. Logically I know any worms would be killed after my planned baking prep, but the lizard part of my brain was all "nope nope nope nope nope".

Your blog has given me hope that I will be able to continue to enjoy my favorite fish food in the future... but perhaps not this week.

Thank you!

Helen Rennie said...

If it makes you feel any better, it took me about a year to get over my disgust of worms in fish. I would still eat it, but it would make me feel a bit yucky if I had to pull worms out of it first. Now, it doesn't bother me.

Anonymous said...

The Cod Worm can kill if it is ingested because it bores a hole in your stomach thus allowing stomach contents to escape. The Law in Holland prohibits selling raw fish that has not been first frozen solid to kill possible worms.