The latest news story in the ongoing saga to make fish forbidden was (unfortunately for the forbidders) a crab and not a parasite found in a can of (non-OU, as far as we know) tuna.
For the record:
1. Tuna sometimes eat crab and other non-kosher fish. They rarely find their way into cans.
2, Even if it would have been the parasite it appeared to be (which is assur since it is found in the fishes mouth, and all agree that bugs found there are forbidden -- See RA"E to YD 84:16 with his version of Sha"ch from wording of gemara) it is found in the head which is not part of commercially processed tuna. Interestingly enough, it eats the tongue of its host and then grabs from everything the fish eats. Ingrate!
3. A single instance of anything forbidden is not basis for forbidding other things. How often does it happen? So infrequently that it was newsworthy. Nuf said.
Bottom line: continue to enjoy your canned tuna without fear of parasites, though if you open a can and see something looking back at you... remove it.