Final answer:
Raw fish like sashimi should be frozen to rapidly drop the temperature and kill parasites. Consuming raw seafood carries risks like tapeworm and herring worm disease, which can cause health issues.
Step-by-step explanation:
The consumption of raw fish including sashimi is safer when the temperature is dropped rapidly, which is a process known as freezing. This is crucial because such a method is effective at killing parasites that may be present in the fish. Eating raw or undercooked fish such as sushi and sashimi can carry the risk of parasitic infections. One of the main parasites of concern is Diphyllobothrium species, which are fish tapeworms that have caused infections due to undercooked salmon. Another concern is herring worm disease or anisakiasis, which is caused by nematodes that can attach to the gastrointestinal tract. To avoid these health risks, it is recommended that fish be frozen or cooked to temperatures that kill off any potentially harmful worms and larvae.