look up the ingredients on heartguard or heartworm medicine that comes from the vet, or red mange treatment... ivermectin used from everything from flea control to mange to heartworms
Noelle,
The active ingredient in Heartworm preventatives such as those you mention is Ivermectin (Ivomec)....it is a preventative that kills ONLY microfilaria. I've read pages upon pages of research data...everything from the Merck veterinary manual to online discussions on common breeder forums and have found NOTHING to prove that Ivomec will actually kill the adult worm. Some believe a regimen of Ivomec on an infected dog can shorten the life cycle of the adult worm while keeping the dog from getting worse thus letting the worms die off and pass naturally...there again no scientific proof, nor are the adult worms actually being killed by the Ivomec.
Nothing that I can find short of Immiticide has been factually proven to kill the adult worm, yet every couple of months someone comes on the site claiming otherwise.
Old time Heartworm detection test kits (which are more than likely still used by some) actually tested for the presence of microfilaria in the bloodstream. Since microfilaria ARE killed by Ivomec, it would be very possible for a dog currently on a preventative to test negative that was indeed positive. This is the reason it was (and commonly still is) advisable to test a dog prior to starting a preventative due to the fact that subsequent tests would result in a negative result.
For sure if I were to have a dog tested that was currently on a preventative regimen, I would question the vet on which test method was being used.
