Heartworm Disease 101

April is National Heartworm Awareness Month, and while it may not come with party hats and cake, it’s definitely a time worth paying attention to—especially if you’ve got a furry best friend at home. Heartworm disease is one of those things that pet parents might know about vaguely, but often don’t think about until it’s too late. Let’s change that.

Whether you’re a seasoned pet owner or a new pet parent, understanding heartworm disease—what it is, how to prevent it, and what to watch out for—can make a world of difference in your pet’s health and happiness.

So, What Exactly Is Heartworm?

Heartworm disease is caused by a parasite called Dirofilaria immitis, which is transmitted through mosquito bites. Yup, you read that right—just one pesky mosquito bite can start the infection process. Once infected, your pet can end up with long, spaghetti-like worms living in their heart, lungs, and blood vessels. 

In dogs, heartworm is more common and can become life-threatening if left untreated. Cats can get heartworms too, but it’s a bit trickier—fewer worms survive to adulthood in cats, yet even a small number can cause severe health issues.

Signs of Heartworm Disease

Heartworm disease is sneaky. It can take months—even up to a year—before symptoms appear, and by then, it’s already doing damage. Some early signs in dogs include:

• A persistent cough
• Fatigue after moderate activity
• Weight loss
• Decreased appetite
• Difficulty breathing

In cats, symptoms may look different and can include:

• Coughing or asthma-like attacks
• Vomiting
• Lack of appetite
• Weight loss
• Sudden collapse (in severe cases)

Here’s the tough part: some pets don’t show any signs until the disease is quite advanced, which is why prevention is so critical.

Heartworm Testing: Why It’s a Must

Even if your pet looks perfectly healthy, regular heartworm testing is essential—especially for dogs. Vets usually recommend testing dogs every 12 months, even if they’re on a prevention plan. Why? Because no medication is foolproof, and early detection gives your pet the best chance at recovery.

Testing usually involves a simple blood test that can be done during your pet’s regular checkup. Easy-peasy and potentially life-saving.

Treatment: Tough but Possible

If your dog tests positive for heartworms, don’t panic—but do act quickly. Treatment can be tough on your pup (and your wallet), but it’s possible. Treatment typically includes:

• A series of injections to kill adult heartworms
• Antibiotics to combat bacteria that live in the worms

• Strict activity restriction to prevent complications
• Ongoing testing and monitoring

Unfortunately, treatment for cats isn’t quite so straightforward. There’s no approved drug to kill adult heartworms in cats. Instead, vets focus on managing symptoms and inflammation while your cat’s immune system works to fight off the infection.

Prevention: The Real MVP

Here’s the good news: heartworm disease is almost 100% preventable. There are a variety of FDA-approved options, including:

• Monthly chewables or tablets
• Topical treatments
• Injections that last 6–12 months (for dogs)

Many of these products also protect against other parasites like fleas, ticks, and intestinal worms, making them a win-win.

Pro tip: Consistency is key. Missing even one dose or giving it late can leave a window open for infection. Set a reminder on your phone, mark your calendar, or ask your vet about long-acting injectables if remembering monthly meds is a struggle.

Busting Common Heartworm Myths

Let’s clear up some of the most common misconceptions floating around:

Myth #1: My pet only goes outside for short potty breaks—so they’re safe.
Truth: Mosquitoes don’t need a long visit to bite. Even indoor pets are at risk, especially during mosquito season.

Myth #2: I live in a cold climate, so heartworm isn’t an issue.
Truth: Mosquitoes—and heartworm—are present in all 50 states. While they’re more active in warmer weather, indoor heating and seasonal shifts make year-round prevention a smart move.

Myth #3: My dog looks healthy, so they must not have heartworm.
Truth: Heartworm can live silently in a dog’s body for months. By the time symptoms appear, damage is already done.

Myth #4: Prevention is too expensive.
Truth: Prevention costs a fraction of what treatment does—not to mention the emotional toll of a sick pet. Many vets also offer discounts or wellness plans that include heartworm prevention.

A Quick Word on Mosquito Control

While prevention meds are your pet’s first line of defense, reducing mosquito exposure doesn’t hurt. Try these tips:

• Eliminate standing water in your yard (birdbaths, buckets, old tires, etc.)
• Use pet-safe mosquito repellents
• Keep windows and doors screened
• Limit walks at dawn and dusk when mosquitoes are most active

Every little bit helps!

Let’s Wrap It Up

Heartworm disease may be scary, but the power to protect your pet is in your hands. A monthly chew, a yearly test, a quick conversation with your vet—these simple steps can spare your pet from pain and keep their heart (and yours) safe.

So this April, as we observe Heartworm Awareness Month, take a moment to check in with your vet. Is your pet up to date on prevention? When was their last heartworm test? A little awareness goes a long way—because when it comes to heartworm, prevention truly is the best medicine.

And while you’re thinking about your pet’s health, it’s also a good time to ask: Do you have pet insurance? Heartworm treatment can be expensive, and having a plan in place can take the financial stress off your plate if your pet ever gets sick. Many insurance plans help cover diagnostics, treatments, and even preventive care—so you can focus on what matters most: your pet’s well-being.

Explore your pet insurance options today and give yourself peace of mind all year long. 

References:

1. https://www.heartwormsociety.org/heartworms-in-dogs
2. https://www.fda.gov/animal-veterinary/animal-health-literacy/keep-worms-out-your-pets-heart-facts-about-heartworm-disease
3. https://www.avma.org/resources-tools/pet-owners/petcare/heartworm-disease

The information contained on this blog is intended for informational and educational purposes only and should not be construed as medical advice. It is not a substitute for professional veterinary care. Always consult with your veterinarian before making any changes to your pet's health care or treatment plan.

The authors of this blog are not veterinarians and do not claim to be experts in pet health. The information provided here is based on our own experiences and research, as well as information from reputable sources. However, we cannot guarantee the accuracy or completeness of this information.

We encourage you to do your own research and consult with your veterinarian before making any decisions about your pet's health.