I feed raw and I'm completely understanding about wanting to keep toxins to a minimum, but I have to say this. Heartworm tests only detect adult heartworms. Your dog could very well have microfilaria circulating in their bloodstream and no adults yet. If you live in an area where heartworm disease is very common, you are taking a huge risk. A few months ago I started giving heartworm preventative every 45-60 days instead of every month because, like you, I wanted to minimize toxins given to my dogs. After seeing literally 100+ dogs test positive for heartworm disease this summer, some even on preventatives, I quickly changed my mind. Heartworm disease is not something to play around with. Treatment is very expensive, up to $1,000 for large dogs, and is much harder on their immune systems than the preventatives which really do not contain THAT high of toxins to begin with. Heartgard is just low dose ivermectin which is also used to treat mange, mites, and some worms.
While I believe raw is awesome and the only way I'll ever feed my pets, it can't prevent heartworm disease. It's spread by mosquitoes so one bad bug and *poof* heartworms. It has nothing to do with how good your dog's immune system is. If you live in an area where heartworm disease isn't all that common then the risk is pretty low. But if you're like me and you live in the south (especially the Mississippi River Valley), your dog WILL get heartworms. It's almost guaranteed. We have like crazy heartworm invested mosquitoes here! But seriously, it's extremely scary. I give my dog heartworm preventative every month and I'm STILL worried after seeing a few dogs with resistant heartworms, luckily paid for by the company.
I hope you don't take this the wrong way. I'm just trying to help. I hate seeing these dogs have to go through the treatment. :frown: