Heartworm, scientifically known as Dirofilaria immitis, is a serious and potentially deadly disease that affects dogs, cats, and several other mammals. The disease is caused by a parasitic worm that resides in the heart, lungs, and blood vessels of infected animals. Some common synonyms for heartworm include canine heartworm disease, feline heartworm disease, dirofilariasis, and filariasis. Other variations of the term may include heartworm infection, heartworm infestation, and heartworm disease syndrome. Preventive measures such as regular veterinary check-ups, heartworm testing, and year-round heartworm prevention medications can help protect pets from this harmful disease.