What is Heartworm Disease?

Heartworm disease is a potentially fatal disease found in the United States and many other parts of the world. It most commonly affects dogs, cats, and ferrets but may also infect other wildlife such as wolves, coyotes, foxes, and even sea lions. This disease, transmitted by mosquitoes, is caused by parasites called heartworms that live in the heart, lungs, and blood vessels associated with these organs. Heartworm disease can lead to heart failure, lung disease, and damage to other internal organs.

Dogs: In the early stages of heartworm disease, many dogs may show few to no symptoms at all. The most common signs noted in dogs include a persistent cough, lethargy and reluctance to exercise, decreased appetite, and weight loss. As the disease progresses, dogs may be diagnosed with heart failure, have a swollen belly from excess fluid in the abdomen, or suffer from caval syndrome- which occurs from a sudden cardiovascular collapse. This is usually diagnosed by the sudden onset of labored breathing, pale gums, or very dark bloody urine. If caught early, heartworm disease can be treated; if left untreated this disease is almost always fatal.

Cats: Heartworm disease in cats is very different from that in dogs. Cats are not natural hosts for this disease, and so most heartworms do not survive to the adult stage. Cats infected by heartworm disease will usually only have one to three immature worms, or microfilaria, and no adult heartworms. Because of this, cats that are infected with heartworms often go undiagnosed. However, these immature worms can still cause damage to their feline host- most commonly known as “heartworm associated respiratory disease (HARD)”. Most importantly though, medication used to treat heartworm in dogs cannot be used in cats, so prevention is the only means currently available to protect cats against heartworm disease.

Source: “Heartworm Basics” by American Heartworm Society, Copyright 2018.