Duane Beckett
Look away, Fillet-O-Fish fast-food fans, as a Reddit post that went viral clearly shows a parasite in the patty. The image, which you can see here, shows a half-eaten sandwich with a round, worm-like creature on the fish.
This is more than enough to send online communities into full-on disgust mode.
However, in recent coverage, Delish reported that commentators in the Reddit thread pointed to a likely explanation. The parasite was a nematode and common in seafood, especially wild-caught seafood, which is what McDonald’s uses in their Fillet-O-Fish across the United States.
Simply put, wild fish can contain these parasites.
Food Republic highlighted that this is why the original story about parasites in a McDonald’s Fillet-O-Fish hasn’t driven more outrage.
The restaurant’s location where the picture was taken has not been confirmed.
McDonald’s stated that it maintains quality control steps for the Filet-O-Fish patty, including freezing the fish in line with FDA guidance, manually inspecting each fillet, and carrying out added inspections at supplier facilities.
None of the above means a visible parasite won’t slip through, but it does mean the company says there are multiple checkpoints before the sandwich reaches a customer.
What are nematodes?
Nematodes are roundworms and can show up in saltwater fish such as cod, pollock, halibut, and flounder. McDonald’s uses pollock in its Fillet-O-Fish.
The CDC says anisakiasis happens when people eat raw or undercooked infected fish or squid, and it advises cooking seafood to at least 145 degrees Fahrenheit.
FDA guidance also says some fish species can contain parasites, and freezing is used to kill them.
So, while not every fillet has a worm, parasites in seafood are common enough that federal food safety rules specifically address them.
Should you still eat it?
If you find a nematode in your Fillet-O-Fish, stop eating it. Even though parasites in fish are not unheard of, spotting a visible nematode in your sandwich is reason enough to stop.
The bigger health risk is usually tied to raw or undercooked seafood, not fully cooked fish. Still, if you find one in a fish patty, toss the rest, keep your receipt if you have it, and contact the restaurant.
If you already ate some, watch for symptoms like stomach pain, nausea, vomiting, or an allergic reaction.
Additionally, the FDA states that older adults and people with diabetes or weakened immune systems should be extra careful with raw seafood, which is the most useful takeaway from this story.