Ivermectin is an unbelievably effective chemical for the prevention of heartworm disease in dogs.  It is readily available over-the-counter, and, when used properly, kills the heartworm microfilariae in a cost effective manner.  Ivermectin is the active ingredient in the Heartguard Plus tablets: the other ingredient in these tabs is Pyrantel Pamoate (kills intestinal roundworms). Ivermectin should never be administered unless it can be established by a blood test that the dog is heartworm negative. In other words, it is strictly a preventative, and has no killing effect on the adult heartworm. Ivermectin is also an extremely safe chemical with a very low incidence of untoward effects or complications. Certain breeds of dogs do exhibit a lesser tolerance for Ivermectin, (Collies, and Collie mixes) but, even in these dogs, severe reactions are rare. I am a licensed wildlife rehabilitator, and also participate in dog and cat rescue. As long as an individual educates themselves about heartworm disease, its ramifications, and other issues pertaining to the administration of Ivermectin, there is no reason that a layperson cannot effectively use this chemical.