Heartworms are a serious disease of an animal's cardiopulmonary (kar-dee-o-PULL-mah-nare-ee) system and generally affect dogs. Worm larvae (LAR-vee) are carried by mosquitoes which ingest the infected blood of one animal and transfer the disease to healthy animals through bites. Once in the blood stream, the larvae migrate to the heart where they can grow into worms as long as fourteen inches. Their presence blocks the flow of blood, making circulation difficult. This is a serious problem which usually results in death if left untreated. Signs of infection can include coughing, and fatigue after exercise and weight loss. Prevention of this disease is most important. It's a good idea to put your animal on preventative medication to protect it against heart worms. Today's medicines are extremely effective and not only prevent heartworms, but can be used to protect against hookworms, roundworms, whipworms, and fleas. Dogs and cats should receive monthly heartworm prevention starting at 9 weeks of age. Older animals need to be tested before starting treatment. For more information on heartworms, contact your veterinarian.