Your furry friend must have a current heartworm test result on file with your veterinarian in order to be prescribed heartworm medication. Please visit your veterinarian to have this test performed annually to protect your four-legged friend. Heartgard Plus is a heartworm preventative that kills heartworms and helps to control and treat hookworms. Given monthly, it comes in a chewable tablet that you can feed to your pal as a tasty, beef-flavored treat. Head back to the dog park, reassured that your dog is protected from nasty parasites.