In a study done on feline heartworm disease, 50 % of the cats with heartworms were indoor only cats. Cats do develop protection against heartworms and the protection is greater in cats that are bitten multiple times by mosquitoes carrying heartworms. Therefore since inside and outside cats can develop heartworms all cat owners should be aware of feline heartworm disease. We are suggesting that everyone consider using Feline Heartgard in their cats whether they are outside or not. In the real world, cats that are inside only will be much less likely to develop heartworms than outside cats. Since the death rate is high in cats with heartworms each cat owner must decide for themselves whether they want to use this new preventive medicine for a potential deadly disease.