Home > Learning Center > Pet Health & Routine Care
Was this page Helpful

Signs That Your Dog Might Have Heartworm

Updated by Amy Granger on Jun 9, 2021

Heartworm disease is a dreaded disease that pet owners need to watch out for. If it goes untreated, it can even be fatal to dogs and other animals. If you suspect your dog has heartworm disease, you will need to take them to the vet right away and seek treatment.

We've put together this handy guide so you can learn more about heartworm disease and notice the signs and symptoms that indicate that your dog might have an issue.

dogs get heartworm

Heartworm disease [Dirofilaria Immitis] is the term that is used to describe parasitic worms that are transmitted to dogs via mosquitos. When a dog is bitten by an infected mosquito, microscopic larvae develop under your dog's skin before migrating to their blood vessels of the heart and lungs.

Once they're inside your dog, they grow rapidly and reach up to 12 inches in length. They're extremely threatening to dogs, as they can cause severe damage to their vessels long before any symptoms are detected.

Your dog is known as a 'definitive host' of heartworms, as the parasite can grow and reproduce in them. Once bitten by an infected mosquito, they grow and reproduce, causing severe damage to your dog's blood vessels. If you live in an area where mosquitos are rife, you will need to take steps to protect your dog from being bitten.

The following can cause dogs to get heartworm:

  • Lack of awareness about heartworm: Many dog owners don't know what heartworm is and how it is transmitted to dogs. By educating yourself on the dangerous parasite, you can take steps to protect your dog from infection.
  • Walking your dog where mosquitos thrive: Mosquitos thrive in wet, humid climates. They're a particular nuisance at certain times of the year, around lakes and open water sources. If you live in an area where mosquitos are an issue, avoid taking your dog to high-risk spots where they might get infected.
  • Poor hygiene: Make sure you regularly treat your dog's coat and remove ticks. If you don't pay attention to your dog's coat, you might miss bites that cause heartworm and other infections.
dogs get heartworm illed

Even if you've taken suitable preventative steps to protect your dog from harm, you can't offer them total protection, and they may be bitten by a mosquito when you least expect it. If your dog displays one or more of the following symptoms, it could be a sign that they have heartworm disease:

  • Mild persistent cough: If your dog has had a mild, persistent cough for a number of weeks, it could be a sign that they have heartworm. Noticing a cough is normally the first sign of the disease in an otherwise healthy dog.
  • Lethargy and tiredness: If your dog has started showing reluctance when it comes to exercise and easily becomes tired, it could be a sign that heartworms are affecting their heart and lungs.
  • Weight loss: Some [but not all] dogs experience weight loss because their appetite is reduced when they're infected with the parasite.
  • Swollen stomach: As heartworm disease gets worse, it can cause your dog's heart to fail. As such, their abdomen will swell from the excess fluid that has accumulated there.
  • Breathing difficulties: If heartworm has existed in your dog for a long time, they are likely to develop severe breathing difficulties as a result.

If you notice any of the above symptoms in your dog, you should immediately take them to the vet to seek treatment. Even if it's not heartworm disease, it could be that your dog is exhibiting symptoms of another underlying health condition that requires medical attention.

Although it's a horrible disease, the good news is that in most cases, heartworms in dogs can be treated. Heartworms are usually treated in the following ways:

  • Medications: Doxycycline and prednisone are commonly prescribed by vets to treat and kill heartworms and manage any unwanted side effects. Some vets may also administer other drugs, depending on the severity of the infection.
  • Surgery: In some severe instances, dogs require surgery to remove the worms from the heart and lung vessels.
  • Exercise restriction: This is a vital stage in the treatment of heartworms. Your vet will guide you on how to restrict your dog's exercise before, during, and after treatment so they don't succumb to the illness

Q1. What are the first signs of heartworm in dogs?

The first sign of heartworm in dogs tends to be a mild and persistent cough. This is because heartworms exist in and around a dog's heart and lungs and causes chest pains and breathing difficulties.

Q2. How can you prevent heartworm in dogs?

Preventing heartworm in dogs is about managing the risk of your dog getting bitten by a mosquito. Keeping your dog inside and away from high-risk areas is an important part of preventing heartworm. You can spray your garden with a heartworm fogger to prevent mosquitos from staying in the area and also purchase some over-the-counter medicine to prevent your dog from being bitten by insects.

Q3. What kills heartworm in dogs naturally?

Some dog owners find success in giving their dog natural oral heartworm preventatives, as well as controlling mosquitos with natural products like citrus oils, cedar oils, and diatomaceous earth.

Q4. If one of my dogs has heartworm, can they give it to my other dogs?

Heartworm disease isn't contagious, meaning it can't be spread from one dog to another. The only way that one or more of your dogs can get heartworm disease at the same time is if they're both bitten by an infected mosquito.


Heartworm disease is an awful, potentially fatal affliction that is caused by mosquito bites. The best way to protect your dog from heartworm disease is to prevent their exposure to mosquitos and to keep them fit and healthy.

You should also regularly look out for the various symptoms of heartworm disease and ensure your dog receives immediate care and treatment if they suffer from the parasite. Catching it early gives them a good chance of recovery.

If you suspect that your dog has been bitten by a mosquito or that they have heartworm or associated diseases or infection, you should seek medical advice from a vet immediately.

Amy Granger
Amy is an editor from iPetor, owns a 4-year experience in writing tips and tutorial for users. As a pet owner, she will share more pets care methods and recommend more useful products for all pet owners.
We use cookies to ensure that you get the best experience on our website. Click here to learn more.Got it