Heartworms are transmitted by mosquitoes so in central Texas they are a year round concern. If your pet is infected, the worms will live in the blood vessels of your dog's or cat's heart. These worms can grow very large and cause severe damage to your pet's heart and lungs leading to heart failure and even death. In dogs, heartworm disease can be treated but it is much easier to prevent. There is no treatment for heartworm disease in cats. We recommend year round heartworm prevention for both dogs and cats as well as annual testing for heartworms in dogs.