They have to test to make sure they aren't infected with heartworms, when they get the medication. I guess if they are already in the heart, the medication would kill the worms, but this isn't good for the heart. You want to kill the worms before they reach the heart. I really don't think there are any cons to taking the medication. It's really safe in that your dog could eat a 6 month supply and not be harmed. We use it in AZ even though there are few mosiquitoes here, the boys love going for walks, and all it takes is one infected mosiquoto. Another reason I treat is it's a very painful disease, if your dog gets it, it will really suffer, some rescues put the dogs to sleep instead of curing it because they say it's so painful and treatment is so difficult. I would never forgive myself if one of my babies got it and I hadn't at least tried to prevent it. |