During the next two-three weeks, the larvae develop within the mosquito into the infective stage. When the mosquito feeds again, it can transmit infective larvae to the healthy dog. The larvae penetrate the dog's skin and migrate through the tissues and develop over the next few months, eventually reaching the dog's heart. Once in the dog's heart, the worms can grow to as long as 14 inches and cause significant damage to the heart, lungs and other vital organs. If left untreated, heartworm disease can result in death.
Every dog can be at risk, indoors or out.
No dog, or breed of dog, is immune to heartworm disease. The first, most important step is to have your dog tested for heartworms. Cases of heartworm disease in cats have been reported across the United States and many other countries, too. Heartworm disease is most common in areas where dogs are also at risk. In fact, most common clinical signs of heartworm disease in cats resembles bronchial asthma.