Heartworms are parasites that dogs and cats can get from mosquitoes. The mosquito bites them, depositing larvae that migrate to the heart where they become adults. Despite fur, mosquitoes can still bite dogs and cats and transmit the disease. To protect your pet it is important to have yearly heartworm testing and keep them on a monthly preventative at home. Usually it is a pill for dogs but cats can have a topical put on their skin. There is no treatment for cats, therefore prevention is imperative.