This roundworm-type parasite infests Jake's stomach after he eats contaminated sushi at Tokyo Toby's. While the parasite usually causes intense abdominal pain within 12 hours of consumption and must be removed surgically, Jake's symptoms are far milder and he is even hungry. The parasite is removed from his throat by Dr. Hask. Afterward, Jake suspects that the worm laid a whole nest of eggs, but he fortunately seems to be mistaken.

(Note - it seems the writers of the episode didn't do their research, as they get everything about this particular type of parasitic infection wrong. Oh well.)