Heartworm Disease In Dogs: Signs and Treatment Options

The warm weather might be fun for your dogs, as they can finally get out and enjoy the sun. However, you still need to watch out, as mosquitoes are also out and flying around. And unfortunately, they are carriers of a parasite that is dangerous to canines called heartworm disease. 

What Is Heartworm Disease?

This parasite is called Dirofilaria immitis, and they love spreading in the heart, blood vessels, and lungs of your beloved pet. This leads to heartworm disease that might cause lung disease, heart failure, and even death. Moreover, it could also worsen other existing health conditions.

These worms get into the body as microfilariae, developing into larvae and growing into adult worms inside. They can survive between 5 and 7 years in all, becoming as long as 4 to 6 inches long in males or 10 to 12 inches in females. Worse, these worms mate inside the body and the offspring are discharged into the bloodstream.

Fortunately, this disease is not contagious from one dog to another, unless the pups are bitten by a mosquito that is infected with the parasites.

4 Stages Of Heartworm Disease

A good heart and a heart filled with heartworms

There are 4 stages of heartworm disease, and there are different symptoms to be observed at every stage.

Class 1 is when the disease is not yet easily distinguishable, and you would only notice a slight cough.

More signs appear by Class 2, and you would most likely observe that your pup is more fatigued than normal. An occasional cough will also signal the disease, and this will turn into a persistent cough by Class 3. 

In Class 3, even light activity will tire your pet out and it might also start to have issues with breathing.

Class 4 is also called caval syndrome. At this stage, there are too many worms in the bloodstream that they block the flow of blood to the heart. This means surgery is needed, otherwise, it will be fatal for your pup.

Fortunately, not all dogs infected with heartworms ever develop to this stage, but identifying the class is necessary to determine a course of action.

Four Most Telling Symptoms of Heartworm In Dogs


Dry Cough: Coughing begins when these parasites find their way into the lungs and begin multiplying. It may also worsen after exercising and in worse cases, might be accompanied by fainting.


Lethargy and Weight Loss: You might notice your pup becoming very tired even without doing anything strenuous. Moreover, it will start being uninterested in playing, going outside, or even doing anything physical. Dogs with this disease are weak and even eating becomes difficult. Over time, it will lose weight due to not eating enough. 

Due to the weight loss, the dog’s chest appears to bulge and the ribs look like they are protruding. This may also be due to the build-up of fluid as the body’s response to the parasite.


Difficulty Breathing: Besides coughing, you might notice your dog having issues with breathing. This happens when the parasite reaches the lungs. At times, fluid also builds up around the surrounding blood vessels, thus it becomes harder for the lungs to provide oxygen to the blood.


Collapse: Once the disease reaches its most critical stage and the parasites invade the heart, collapse happens. This might also be accompanied by shock, as well as the destruction of the red blood cells. This signals that death might not be so far away, and it is critical at this stage to be operated on.

Prevention and Treatment

Dog getting medication to prevent heartworms

Heartworm disease sounds scary, and it can be serious. However, getting a positive diagnosis is no death sentence. If caught early, it can be treated successfully.

The first step of treatment is to reduce physical activity in order to reduce the damage to the lungs and heart. Use a good GPS tracker to monitor your dogs activity and health. Once stable, antibiotics might be prescribed against infection. Heartworm preventive medication is also necessary to kill any small larvae left behind and to reduce inflammation, your pup might be given some corticosteroids.

To kill the adult worms, injections or topical medications will be used. While effective, these medications are actually toxic and have serious complications so your vet will monitor the treatment carefully. If necessary, surgery might be performed to get rid of the heartworms.

The treatment will take months, which is why dog owners should take the necessary precautions to avoid infection in the first place. This is uncomplicated but requires commitment and regular visits to the vet.

The doctor can prescribe an oral pill or a topical medication that should be taken monthly. It is, however, vital that it is taken every month in order to provide full protection. If you miss a dose and you suspect an infection, your vet can also take a test.

Final Thoughts

Although heartworm has been reported more often in warmer states, they are now spreading nationwide, especially when there are warmer summers. This is why understanding heartworms is important to save lives. The good news is, as a dog owner, you only need to add heartworm prevention as part of your care for your beloved pet and you will be able to avoid this serious disease.

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