Heartworm in Dogs: Causes, Symptoms and Treatments

Do you know that a single bite from an infected mosquito can jeopardize your dog's health? It’s true — mosquitoes can carry heartworms, which they can transmit to your dog through a bite.

Heartworm disease is a life-threatening condition in dogs, but fortunately, it is completely preventable. Learn all about heartworm disease and ways to keep your four-legged family member safe.

What Is Heartworm Disease in Dogs?

Heartworm disease in dogs is a life-threatening heart and lung disease caused by the parasitic worm Dirofilaria immitis. After entering a dog’s body, microscopic heartworm larvae migrate to the large blood vessels of the lungs, which lead to the heart.

Timeline

Over the course of six to seven months, the larvae mature to 12-inch-long, spaghetti-like adult worms that begin to reproduce. Over time, the worms multiply, filling the blood vessels and the right side of the heart. 

Symptoms

Heartworm disease does not typically cause signs until adult worms begin to accumulate in the blood vessels and heart. Considering the worms’ long maturation period, this means that dogs may not show signs until several years after infection.

When signs do appear, they may include:

• Coughing
• Decreased appetite
• Lack of energy
• Lethargy
• Weight loss

The worms’ presence causes inflammation in the blood vessels and heart. They also interfere with normal blood flow, leading to congestive heart failure. Without treatment, heartworm disease can lead to death in infected dogs. 

Cat vs. dog heartworm

Cats can also get heartworm disease, but the worms cannot multiply in cats. However, this doesn’t mean that cats don’t develop disease — the few worms present can cause significant inflammation, leading to breathing problems and sudden death. 

What Causes Heartworm Disease in Dogs?

Heartworms are transmitted to dogs by infected mosquitoes. When a mosquito bites a dog (or a wild canine, such as a wolf or coyote) with heartworm disease, it picks up microscopic heartworm larvae circulating in the dog’s blood. The larvae can then be passed to other dogs through a mosquito bite.

Heartworms cannot be passed directly from an infected dog to other animals, including other dogs or cats within their household. However, the presence of an infected dog makes it more likely that mosquitoes in the area will carry heartworm larvae. 

Diagnosing Heartworm in Your Dog

Heartworm disease is diagnosed using a simple in-office blood test. After collecting a few drops of blood from your dog, your veterinarian will be able to give you results in about 10 minutes. Alternatively, your vet may send the blood out to a laboratory for testing, in which case you should receive results in a few days. The national average cost* of a heartworm test is $71, and ranges from $56 to $128.¹

Annual heartworm testing is recommended for all dogs during their yearly wellness visit. Although preventing heartworm disease is the best scenario, annual testing allows your veterinarian to detect heartworm disease early, before significant damage and heart failure develop.

Treating Heartworm

If your dog tests positive for heartworm disease, they will require treatment to kill the adult and larval worms in their body. Treatment involves injections of an arsenic-based compound over several months, as well as antibiotics and anti-inflammatory medications. According to the American Heartworm Society, the average cost of heartworm treatment for a 40-pound dog is $1,200 to $1,800.²

During the treatment period, dead worms can potentially lodge in the blood vessels of the lungs, causing a life-threatening pulmonary embolism. To minimize this risk, dogs undergoing treatment must adhere to strict activity restrictions. 

Preventing Heartworm

Fortunately, heartworm disease is a preventable condition. The American Heartworm Society recommends year-round administration of a heartworm preventive containing a macrocyclic lactone drug (i.e., ivermectin, milbemycin oxime, moxidectin or selamectin).³

Veterinary-approved heartworm prevention medications are available in various forms — including oral, topical and injectable options — which makes dosing easy for pets and pet owners. The average monthly cost* for heartworm prevention in the United States is $14, but it can range from $11 to $25, depending on where you live.¹

Simply put, the cost of prevention, in terms of finances and your dog’s health, is far less than treatment. 

Home remedies for heartworm in dogs

There are no effective home remedies that can be used to prevent or treat heartworm disease in dogs. If your dog is not currently on heartworm prevention, ask your veterinarian what medication they think is best for your dog’s lifestyle and situation.

Getting to the Heart of the Matter

Heartworm disease is a serious, life-threatening condition that affects dogs across the U.S. Annual heartworm testing and year-round prevention are essential parts of your dog’s routine wellness care. Knowing about the disease and the steps you can take to protect your dog can help you keep them safe and healthy for years to come.

CareCredit Credit Card Financing for Dogs

The CareCredit credit card provides a convenient way to pay for your dog’s vaccinations and other health and wellness expenses, including exams, medications and products at providers in the CareCredit network.** Continue your wellness journey by downloading the CareCredit Mobile App. You can find a provider on the go, manage your CareCredit account and easily access the Well U blog for more great articles, podcasts and videos. Use our Acceptance Locator to find a veterinarian that accepts CareCredit to help keep your pet healthy and happy for a lifetime of love.

In addition to pet care, you can also use your CareCredit credit card for dentistry, cosmetic, vision, hearing, health systems, dermatology, pharmacy purchases, spa treatments and so much more within the CareCredit network. How will you invest in your health and wellness next?

Author Bio

Angela Beal, D.V.M., has more than 20 years of experience as a veterinarian. Leveraging her background in private practice and academia, she uses her passion for writing to convey information to pet owners to help them keep their pets healthy and happy.