Hey Bz,
The reasoning behind the heartworms tests is to determine how severe the infection is.
Heartworm medication is a preventative medication. If your dog has heartworms, and you give it the preventative monthly doses (Ivermectin for example), the dosage is only sufficient to prevent the heartworms from colonizing / proliferating in the tissue. The monthly preventative medications will not be strong enough to kill all the heartworms present. It may take between 2 and 3 years for the monthly preventative medication to kill the heartworms in a dog (or whatever other infected animal) with a pre-existing heartworm infection (the length of time for the medication to do the job depends on how severe the infection is).
In the meantime while you think your dog is protected from heartworms, the worms that are already in the dog are still eating away at the tissues, so your dog likely will die before the heartworms do.
That is why veterinarians pre-screen for heartworm infections. To treat a pre-exisiting heartworm infestation, stronger drugs that work much more quickly are needed, such as Immiticide.
Once the heartworms have been treated with the stronger drug and are all gone, you can begin administering the monthly preventative heartworm medication to keep them from coming back.
Since your dog seems to get yeast infections often, it is a chronic condition. I would just have your veterinarian pay you a visit and ask him if he might be able to write you a one year prescription (as esshup suggested) so that you can keep it on hand. That wouldn't be an unreasonable request in my opinion.
Just as a caution, if you are planning to use Ivermectin as a preventative heartworm medication, then keep a close eye on your dogs. Ivermectin isn't as commonly used as it used to be because it is common for dogs to have severe allergic reactions. I would talk to your vet about it, but it is pretty obvious if they have an allergic reaction. Common in veterinarian medicine is around a 5% chance of it happening, so the risk of an allergic reaction really isn't that steep if you put things into perspective.
Last edited by Gflo; 12/22/10 02:08 PM.
