What happens when your dog has heartworms?

Being the owner of a dog or a cat, it is important that you learn about all of the different health elements that you need to be aware of.  Although your dog will be vaccinated for a lot of harmful health problems, you should be aware of other symptoms that tend to be less common, such as those related to heartworms. If you have any questions about heartworms, do not hesitate to talk to the veterinarian on your next appointment.

Some infected dogs may not develop the disease. However, these dogs become carriers: they will carry the larvae on their skin or in their body, but not in the heart. If the parasites start developing around the lungs or in the heart, the dog can become very ill.

Damages to pulmonary arteries by heartworms.

Heartworms can damage the pulmonary arteries within days after establishing themselves in those arteries. Because they are too big, the immune system of the infected animal is unable to destroy them. This will first cause inflammation, then, if the damages to the arteries become more severe, aneurysms and blood clotting are formed, causing arteries to plug up. These will result in a lack in oxygenation of the dog’s lungs. This is why infected dogs can show quick exhaustion following exercise, lots of coughing, nose bleeds and even a form of non contagious pneumonia (pulmonary eosinophilic granulomatosis)..

Heart failure from heartworms.

If the heartworms locate themselves in the arteries of the dog’s heart, arteries will plug up, forcing the heart to work harder and faster to let the blood flow through the body (hypertension).

Sometimes, the right side of the heart weakens and some fluid accumulates in the chest and in the abdomen of the dog, creating a belly-like appearance and difficulty to breath.

In severe cases, the heart thickens from overworking and starts acting differently. This can lead to the disruption of the heart contractions, creating an arrhythmia and sudden death of the dog.

Chronic stimulation of the immune system.

The presence of heartworms in the dogs will trigger its immune system to respond. Because antibodies are sent on a regular basis, this leads to chronic inflammation. This chronic inflammation can cause damages of the surrounding cells, triggering some damages to the tissues and a lot of pain for the dog.

Caval syndrome.

Caval syndrome is an aggravated version of heartworm disease. Sometimes, the parasites can proliferate (as much as 100) and fill up the entire heart of the infected dog. This happens when the unfortunate animal shows no signs of heart problems prior to the caval syndrome. Because it is so severe, the dog will collapse and death will usually occurs within 1 or 2 days unless surgery is performed.

Other possible syndroms.

Rarely, the heartworm larvae can migrate to unusual sites, such as the eye, the brain or a leg, leading to some unusual symptoms such as blindness, seizures and difficulty to move.


Prevent heartworms. Talk to your vet today.