Some unreasonable people resort to personal insults or ridicule or defamation when they have no convincing argument.
The question is simple : where is your objective proof (dead parasitic worms) that the electric current produced by a zapper can kill all kinds (or atleast one kind) of parasitic worms in a human body ?
All zapper sellers should be able to provide at least one convincing experiment and result, but after all these years, there is nothing.