Myth 5: Heartworm Disease Is Rarely Fatal
Heartworm disease is a devastating and potentially fatal disease, impacting the heart, lungs, and pulmonary blood vessels, Hatton says. “Heartworms lead to an inflammatory reaction that can cause permanent damage to the blood vessels in the lungs. Apart from the risk of fatality, heartworms can compromise an animal’s quality of life and cause debilitating clinical signs and symptoms which may improve, but not necessarily resolve, even with treatment.”
In dogs, symptoms usually start with a cough, which can worsen as the disease progresses. “Fatigue, difficulty breathing, and weight loss are common later in the disease,” Hatton says. “Left untreated, dogs can go into heart failure and ultimately die.”
Cats with heartworm disease typically develop lung disease, which can mimic asthma and cause respiratory distress, chronic coughing, and vomiting, she says. “The death of one adult heartworm in a cat can cause that cat to die abruptly.”
How Long Can a Dog Live With Heartworms?
"[Heartworm] life expectancy depends on the size of the dog, the relative health of the dog, if the dog has a reaction to the worms, and how many worms the dog has," says Dr. Sarah Wooten, DVM, at West Ridge Animal Hospital in Greeley, Colorado.
However, left untreated, heartworm disease is usually fatal, Jeffrey says. “Some dogs can carry a very low worm burden and be OK, but the majority of dogs who go untreated will not survive.”