To the best of my knowledge anchorworms require an intermediate stage to infest so usually are only a problem in ponds(used to have alot in my pond, but apparently after the pond matured they dissapeared and I haven't seen any in years).
Their is a treatment for pond use only. Pulling them off works(apparently after the above post!) but is quite traumatic and I'm sure you'd kill just as many as you'd save that way. You'd have to make sure to remove the entire worm, mouthparts included so to prevent a secondary infection.