Heartworms are an invasive parasite that can make your dog very sick and if untreated, can kill him. A mosquito that has fed off an infected dog can pass heartworm larvae to your dog by biting him. Once in your dog’s body, the heartworm larvae mature and grow into large worms that will clog your dog’s blood vessels, lungs and heart. This causes respiratory and circulation issues that can destroy organs. There are treatments to rid your dog of heartworms but they are expensive, may require surgery and may not improve your dog’s health. Fortunately, there are oral preventative medications available by prescription. These medications need to be given to your dog monthly all year round since just a few warm days can make mosquitoes active. Your dog will need periodic blood tests to ensure he hasn’t been inadvertently infected with heartworms. Learn more from your Cy-Fair veterinary clinic.