[Joe 6-pack]

It does seem to work. Even with the prevalence of heart worm here in Louisiana, my dog has been on ivermectin for years. No problems.

[YoungCurmudgeon]

I am one of those money grubbing veterinarians many on this thread seem to suddenly despise. As a public service I have to comment on the use of ivermectin for prevention of heartworm. Yes, it is effective. It is the active ingredient in Heartgard, but it is extremely toxic to Shelties, Collies, and dogs who are collie or sheltie mixes. It will cause seizures and neurological damage in these breeds and may result in a very nasty, slow death. Just thought everyone should be aware.