Does sushi have parasites?
I have heard that the ingestion of raw, or lightly cured, or insufficiently cooked infected fish can transfer the live worms to humans. But, most of these parasites cannot adapt to human hosts.
The parasites present in fish are in their gut. The life cycle of these worms is that once an animal dies the parasites sense this and move out of the gut, through the intenstinal walls and into the flesh in preparation to be eaten.
When a fish is caught and processed immediately (gutted) virtually all chance of this happening disappears.
Further, most fish that is called Sushi Grade is flash frozen at sea, which also kills virtually all of these parasites that might have snuck in there. When in doubt, excellent sushi chefs will check a very thin slice (think of a piece of lox) and hold it up to the light ... the worms are large enough to be visible.
These worms are not the common tape worms that humans have been plagued with for millions of years. The Anisakiasis larvae can come from ceviche or sushi. They can cause nausea, vomiting, cramps, abdominal pain and intestinal gas. It will usually pass though (and it's highly likely that most cases of infection go unreported because they resolve themselves).
It is safe to eat saltwater fish raw, however, eating raw freshwater fish is not so much.
Think on it for a moment, there is no trout or carp (or other freshwater fish offered on sushi menus) for a reason. These eggs and parasites will survive the GI tract and make life "interesting". I believe that it is osmotic shock that does marine parasites in the GI tract.
Salmon and eel do not count as freshwater because move between fresh and saltwater, however, I would not be eating either raw while the young had yet to migrate out into the ocean -after they come back into freshwater, acquired marine parasites die and they are safe.
Part of what a sushi chef does while preparing the food is inspect for freshness, parasites, etc. In the US "sushi grade" is handled to reduce the risk of parasites. The term can be loosely used, so question your fish source to be sure that the fish is meant to be eaten raw. This site has some good info:
There have been threads about this in the past that had some good details & insights!
While they may not "adapt"to human hosts, there have been news stories (not urban legends) about them sending people to the hospital for emergency surgery, at least with home-prepared fish. Supposedly, restaurant chefs are adept at identifying the culprits and getting rid of them.
There is "sushi-grade: fish for sale; but then again, there is much "wild salmon" for sale that is farm-raised.
Don't know about sushi in particular but I was told by a friend who is an infectious disease doc that a healthy human immune system can kill off parasites found in raw fish/meats or undercooked meats. A compromised immune system ( can mean everything from serious illness like AIDS to being run down and having a cold) may not be able to rid the body of parasites so it is best to avoid uncooked foods.
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