That impulse to find a more hospitable environment, Sakanari says, is what makes anisakids particularly worrisome for humans. The human body is sufficiently different from that of whales and elephant seals—typical anisakid end hosts—that it forces the worms to wander around inside of it. As they do so, they probe along the intestinal wall, trying to penetrate it and sometimes getting stuck in the process, which can necessitate resection. (Interestingly, because humans are a natural end host for tapeworms, Sakanari says that tapeworm infection, as disgusting as it might sound, would be preferable to larval anisakid infection. The pathologies associated with the adult fish tapeworm infection are by and large less severe, and can be treated with a simple anthelmintic.)
The upshot of all this: The only real way to be sure that you’ve eliminated any parasites in the flesh is by using temperature. “It’s best to properly freeze or cook the fish. That’s the bottom line,” Sakanari says. Is it worth the risk to eat raw fish that hasn’t been properly frozen? “It depends on how much you love the dish,” she says. “There are always risks to eating anything raw and improperly prepared or washed, so it is incumbent upon consumers to be aware of the risks and how to prevent the infections.”
