Either vinegar or lemon squeeze, basic sterile act by using the acid to kill parasites, or on minimum by sprinkling salt.I dunno about some regions, but in my country, they are marinated in vinegar first. They are also related to mollusks so they are safe to eat (it takes courage to eat for first timers though).
Eating raw oyster from its natural habitat often still have live parasite, but I don't know about worm. The fact that dude go RAW hands down, despise knowing it carry the risk of parasite and how bad it is for them if there is a living parasite in their stomach, is kinda off.
UNLESS worm TRULY has no parasite.