Heartworm disease is a serious disease that results in severe lung disease, heart failure, other organ damage, and death in pets, mainly dogs, cats, and ferrets.
It is caused by a parasitic worm called Dirofilaria immitis.The worms are spread through the bite of a mosquito. The dog is the definitive host, meaning that the worms mature into adults, mate, and produce offspring while living inside a dog. The mosquito is the intermediate host, meaning that the worms live inside a mosquito for a short transition period in order to become infective (able to cause heartworm disease). The worms are called “heartworms” because the adults live in the heart, lungs, and associated blood vessels of an infected animal.
In the United States, heartworm disease is most common along the Atlantic and Gulf coasts from the Gulf of Mexico to New Jersey and along the Mississippi River and its major tributaries, but it has been reported in dogs in all 50 states.
What Are The Symptoms Of Heartworm Disease In A Dog?
According to the FDA,there are four classes, or stages, of heartworm disease. The higher the class, the worse the disease and the more obvious the symptoms.
Class 1: No symptoms or mild symptoms such as an occasional cough.
Class 2: Mild to moderate symptoms such as an occasional cough and tiredness after moderate activity.
Class 3: General loss of body condition, a persistent cough, and tiredness after mild activity. Trouble breathing and signs of heart failure are common. For class 2 and 3 heartworm disease, heart and lung changes are usually seen on chest x-rays
Class 4: Also called caval syndrome. There is such a heavy worm burden that blood flowing back to the heart is physically blocked by a large mass of worms. Caval syndrome is life-threatening and quick surgical removal of the heartworms is the only treatment option. The surgery is risky, and even with surgery, most dogs with caval syndrome die.
For more info on heartworm disease, watch this video from American Heartworm Society
What Are The Symptoms Of Heartworm Disease In Cats?
According to the FDA, not all cats with heartworm disease show symptoms. Many cats are able to spontaneously rid themselves of heartworms without showing symptoms. However, some infected cats die suddenly from heartworm disease without ever showing signs of being sick.
In cats that show symptoms of heartworm disease, respiratory signs are the most obvious due to the lung damage caused by the heartworms. Cats typically show symptoms of heartworm disease at two time points – when the immature heartworms arrive in the heart and lung arteries and when the adult heartworms die.
The immature heartworms arrive in the heart and lung arteries about three to six months after a cat is bitten by an infected mosquito. Many of these immature heartworms die, causing a strong inflammatory response in the cat’s lungs. This response is called heartworm associated respiratory disease because respiratory signs, such as trouble breathing, increased respiratory rate, and cough, are the most obvious. It may be difficult to distinguish HARD from feline asthma or feline bronchitis.
Often, cats with heartworm disease show very nonspecific symptoms that mimic many other cat diseases. These nonspecific symptoms include vomiting, decreased activity and appetite, and weight loss. Cats with heartworm disease rarely show signs of heart failure.