Heartworm is apparently different from the intestinal worms. Heartworms are actually worms that are transmitted by mosquitos only. That's why the odds of an indoor kitty getting them is so high. I don't think I've seen a mosquito in two years easy. Just takes one of those little suckers to infect. Heartworm is much more common in dogs because they go outside. The original diagnosis may just be the larve (sp?) Just as Sia1 explained. Wish I never had to learn about any of this.