Mike:
>Fei, my wife, had some oysters for the day before yesterday’s dinner. After
>she finished we saw a kind of worm about 2 cm long and 0.5 mm wide moving
>in the oyster water on the plate. I wonder if anybody knows if there are
>parasites in oysters that might be dangerous for humans.

I do not have an answer, but another experience.  I thouroughly enjoy raw
fish such as tuna, swordfish (not very often), and salmon.  I did, however,
find a _wriggling worm_ in a piece of halibut that I bought!!  Oh, it about
made me _hurl_.  It was also about the size of the worm you describe.  That
experience left me so grossed out that I didn't eat fish for a month or so
after that.   Today I am not absolutely concerned with fish parasites; at
least not to the point of stopping consumption of raw fish.  I still enjoy
the other fish above, but my experience made me _very_ preoccupied with
checking the fish out with a fine-toothed comb.  yuck.

slimiest regards,

Ben