How to Recognize Heartworms in Dogs?

Heartworm disease is the most common illness in dogs caused by worms known as ‘Dirofilaria immitis’ which is spread by the infected mosquitoes. These worms mature into adults while living inside your dog’s internal organs such as heart, lungs and blood vessels. If not diagnosed and treated on time, the illness results in heart failure, acute lung disease; other organ damage and even death.

How to Spread Heartworm?

When a mosquito bites an infected animal, it takes the worms in with the blood-meal. Now, if this mosquito bites your dog, it transmits microfilariae into your dog’s blood vessels that become larvae which develop into adult worms and then the cycle continues. It is critical to know that a dog infected with heartworm does not transfer the illness to other non-infected dogs. The heartworm disease is only spread by an infected mosquito.


Heartworm disease is famously known as a silent killer in dogs as the initial stage of the illness shows very limited or even no signs at times. It is more likely that the disease has already spread by the time the alarming signs appear. So, it’s critical that you be attentive to any of the following signs your dog shows:

1.Dry and Persistent cough

Dissimilar to normal cough, in heartworm infection, worms move through lungs and start reproduction inside the organ that results in dry and consistent coughing.

2.Lethargy or Inactive

Dogs infected with heartworms generally do not show much interest in any physical activity and become lethargic. They will show signs of extreme weakness even in the activities that do not require much energy.

3.Loss of appetite and weight loss

When the heartworm infection advances in your dog’s body, your dog will find it difficult to complete the diet he used to finish in no time. This is ultimately leading to weight loss.

4.Difficulty in breathing

Your dog starts to breathe rapidly or struggles while breathing at a stage when the worms occupy your dog’s lungs and associated blood vessels.

5.Distended (Enlarged) chest

A swollen or bulged chest is an indication of the adult heartworm infection that is usually caused by fluid buildup.

6.Fainting or Collapsing

Fainting or collapsing in dogs usually happens when a large number of worms cause vein blockage in the heart and destruct red blood cells. This stage is known as caval or vena cava syndrome which more often than not results in death.


If you notice any of the symptoms mentioned above or any other abnormal signs related to your dog’s breathing, immediately consult a veterinarian.

The vet will ask to perform a blood test that detects heartworm infection. If the dog is heartworm positive, your vet recommends further testing to decide the treatment plan.

Ideally, heartworm test should be performed on a regular basis even in dogs taking heartworm preventatives because you never know that your dog might be throwing up the heartworm pill that you have been giving him or washing off the topical treatment.

Read : Heartworm Disease In Pets – Signs & Treatment


Comparison of Heartworm Preventives

One of many consequences of the heartworm infection is that it requires a prolonged treatment to kill the existing heartworms. The treatment is brief, expensive and tiring that can really take a lot out of both you and your loved animal. This is why most veterinarians recommend a year-around preventative treatment and regular testing for heartworm infection. Heartgard Plus, Interceptor Spectrum, and Revolution are some of the popular brands that will help you prevent heartworm infection in your dog. Make sure that you use any heartworm preventative treatment on your dog only after consulting a veterinarian.