Parasite PreventionHeartworms, intestinal parasites, fleas, and ticks are the most common parasites that can cause or transmit disease to your pets and in some instances to pet owners. Monthly oral and/or topical products can prevent these infestations and keep your family safe and comfortable. Heartworms are transmitted by mosquitoes and damage the heart and lungs. Treatment for heartworm disease costs hundreds of dollars while prevention costs just a few dollars a month. Heartworm prevention also protects against the most common intestinal parasites. Fleas and ticks are prevented with are either a topical or oral monthly treatments.