Home - Pet Health

What are the signs and symptoms of heartworm in a dog?

Heartworm isn't something to brush off—it's a serious condition that can sneak up on even the most attentive pet owners.These tiny parasites,spread by mosquitoes,settle in a dog's heart and blood vessels,and by the time obvious issues pop up

Heartworm isn’t something to brush off—it’s a serious condition that can sneak up on even the most attentive pet owners. These tiny parasites, spread by mosquitoes, settle in a dog’s heart and blood vessels, and by the time obvious issues pop up, they’ve often been causing damage for months. Catching it early makes treatment way easier, so knowing what to look for could save your pup a lot of suffering. Let’s start with the subtlest clues: a dog with early-stage heartworm might get winded faster than usual, even on short walks. That playful fetch session in the yard? They might tap out sooner, lagging behind or plopping down when they’d normally keep going.

As the infection progresses, those small changes can turn into more noticeable problems. A dry, hacking cough is common—especially after exercise—because the worms irritate the lungs and heart. You might notice your dog seems less interested in food, dropping a few pounds without trying. Their gums could look paler than usual, a sign that their body isn’t getting enough oxygen. In some cases, their belly might swell a bit, making them look bloated even if they haven’t eaten too much. These aren’t just “off days”—they’re red flags that something’s wrong, and ignoring them can let the worms multiply, making treatment harder and riskier.

Dogs in areas with lots of mosquitoes need extra attention, but heartworm isn’t limited to warm climates—those pests stick around longer in many places these days, thanks to milder winters. Even indoor dogs aren’t totally safe; a single mosquito slipping through an open window can carry the infection. That’s why regular vet check-ups are a must. Most clinics offer simple blood tests that can spot heartworm before symptoms show up, which is key because early treatment is far less stressful for your dog. Some regions even recommend year-round prevention meds, tiny pills or chewables that keep heartworm from taking hold in the first place—ask your vet what works best for your area.

It’s important to remember that prevention is way easier than treatment. Heartworm medication is safe, affordable, and often covered by pet insurance plans, which many owners find helpful. Skipping it to save a few dollars can end up costing thousands later, not to mention the heartache of watching your pup go through intensive treatment. Plus, keeping your dog protected fits with local guidelines in many communities, where responsible pet ownership includes preventing the spread of parasites that can affect other animals too.

If you do notice any of these signs—sluggishness, coughing, weight loss, pale gums, or swelling—don’t wait to call the vet. They can run tests to confirm heartworm and outline a treatment plan. It might involve a series of injections and plenty of rest for your dog, but with care, most make a full recovery. The worst thing you can do is hope it goes away on its own—heartworm won’t clear up without treatment, and letting it progress can lead to heart failure, which is tragic and often fatal.

Your dog can’t tell you when they’re hurting, so it’s up to us to stay alert. Those little changes in their energy, their coughs, their appetite—they’re all ways they’re trying to tell us something’s wrong. By knowing the signs, staying on top of prevention, and seeing the vet at the first hint of trouble, you’re giving your pup the best chance to stay happy, healthy, and ready for all the walks, playtime, and snuggles that make life with a dog so wonderful.

Related Articles