One way to “kill” parasites is to freeze the fish. Here is a detailed procedure recommended by FDA in the United States: In short, you can kill some, BUT NOT ALL, parasites by freezing for (roughly) 48 -72hours in your home freezer. read more
Any other saltwater parasite in the fish is just extra protein. But freshwater fish have parasites which can transfer easily to man and therefore freshwater fish are to be avoided as a sushi fish. You will not get sushi panga nor sushi tilapia nor sushi carp. read more
The Japanese fishermen, and fish mongers have known about parasites in seafood for hundreds of years, and know which fish are safe from them. Not all fish are consumed raw in Japan for this reason. Only the ones that have minimal or no chances of having parasites have been used for sashimi or sushi. read more