The first descriptions of heartworm infection in cats was documented in the early 1920's 2,3 . Now, naturally-acquired heartworm infection in cats and dogs is recognized as a worldwide clinical problem, and despite improved diagnostic methods, effective preventives and increasing awareness among veterinary professionals and pet owners, we continue to document cases of heartworm infection in dogs around the world, and the diagnosis of the disease is still rather complex and elusive in cats. Heartworm disease is a serious and potentially fatal condition of worms residing in the heart and major blood vessels of dogs, cats and other species of mammals, including wolves, foxes, ferrets, sea lions and humans.
Dogs harboring adult worms are the recognized reservoir of infection.
In the dog, the larvae progress in their development to an adult form of the worm, and live in the heart and pulmonary vessels, where they continue the life cycle and cause extensive injury. In the cat, the larvae molt as well, but fewer worms survive to adulthood. While dogs suffer severe heart damage from heartworm infection, cats typically exhibit minimal changes in the heart. The cat's primary response to the presence of heartworms occurs in the lungs, and the host's response to the parasite is intense. Cats more typically are considered dead-end hosts , because they rarely have microfilariae to continue the life cycle.