Most horse owners understand that parasitic worms pose a serious threat to the health of their animals, but few understand that different kinds of worms do damage at different life-cycle stages. This brochure, developed for veterinarians, was designed to explain the use and limitations of various classes of de-wormers. A flip chart shows what each parasite looks like during its life cycle, where it damages the horse, and which parasiticides are effective at which stage of the parasite’s development.