If you’re a dog owner, you’ve probably heard about heartworms—but do you really know how to spot the symptoms?
Here’s the scary truth: By the time most dogs show signs of heartworm disease, the infection is already severe.
Heartworms are parasitic worms transmitted through mosquito bites. Once inside your dog, they grow, multiply, and invade the heart, lungs, and blood vessels—causing serious, sometimes fatal, damage. The earlier you catch the signs, the better the chances of saving your dog.
So, how do you know if your dog has heartworms? Let’s break down the seven most important symptoms you need to watch for.
1. Persistent Coughing
A lingering cough that won’t go away is often the first red flag. Unlike the occasional throat-clearing cough from dust or excitement, a heartworm-related cough is:
✔ Dry and persistent
✔ Triggered by exercise
✔ Not relieved by water or rest
Why It Happens
As heartworms grow, they block blood flow to the lungs, causing inflammation and irritation in the airways. This makes it harder for your dog to breathe properly, leading to a chronic cough.
🚨 Red Flag: If your dog starts coughing after short walks or mild play, it’s time to see a vet ASAP.
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2. Fatigue and Reluctance to Exercise
One day, your dog is full of energy. The next? They’re lying around all day, barely interested in their favorite activities.
Why It Happens
Heartworms disrupt oxygen flow in the bloodstream. Less oxygen = less energy. The heart and lungs work overtime trying to pump blood through clogged arteries, leaving your dog exhausted.
🚨 Red Flag: If your normally active dog suddenly avoids walks, playtime, or even struggles to stand after rest, don’t ignore it.
3. Weight Loss and Muscle Wasting
Heartworm disease makes it hard for dogs to maintain a healthy weight. The energy they should be using to digest food and build muscle is instead spent fighting the infection.
What You Might Notice
✔ A sunken or “tucked-up” stomach
✔ Ribs and spine becoming more visible
✔ Loss of appetite
In severe cases, heartworm-infected dogs develop “cardiac cachexia”—a condition where the body breaks down its own muscle to survive.
🚨 Red Flag: If your dog is eating normally but still losing weight or looking frail, it’s time for a vet visit.
4. Swollen Belly (Fluid Retention)
A bloated, swollen belly might look like weight gain, but in heartworm cases, it’s actually fluid buildup caused by heart failure.
Why It Happens
When the heart struggles to pump blood, fluids leak into the abdomen—causing swelling. This condition is called ascites and is a serious warning sign.
🚨 Red Flag: If your dog’s stomach is noticeably swollen and they’re also breathing harder than normal, get them checked immediately.
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5. Difficulty Breathing
If your dog seems to be struggling to catch their breath, don’t ignore it. As heartworms clog the lungs and blood vessels, oxygen flow is restricted, leading to:
✔ Fast, shallow breathing
✔ Panting even when resting
✔ Extended neck and wide stance while breathing
Why It’s Dangerous
As the lungs fill with fluid, your dog might develop heartworm-associated respiratory disease (HARD)—a serious condition that makes it nearly impossible to breathe normally.
🚨 Red Flag: If your dog’s tongue or gums turn blue or purple, it means oxygen levels are dangerously low. This is a medical emergency.
6. Collapse or Fainting
Dogs with severe heartworm infections may experience sudden collapse or fainting spells—especially after activity.
Why It Happens
Heartworms block major arteries, making it difficult for the heart to pump enough blood to the brain. This can lead to:
Sudden weakness
Staggering or falling over
Brief loss of consciousness
🚨 Red Flag: If your dog collapses or faints, go to an emergency vet immediately. This is a sign that the infection is life-threatening.
7. Pale or Dark Gums
Checking your dog’s gums is a quick way to assess their health. In heartworm-infected dogs, you may notice:
✔ Pale or white gums → Signs of anemia and poor circulation
✔ Dark red or bluish gums → Lack of oxygen due to heart and lung failure
How to Check
- Gently lift your dog’s lip.
- Press on the gums with your finger until they turn white.
- Release—healthy gums should turn pink again within 1-2 seconds.
If they stay pale or dark, it’s time to call your vet.
How to Protect Your Dog from Heartworms
The best way to deal with heartworms? Prevent them before they start.
💊 Use monthly heartworm preventatives. Prescription meds like Heartgard, Sentinel, or Advantage Multi kill heartworm larvae before they mature.
🦟 Reduce mosquito exposure. Since mosquitoes spread heartworms, using flea-and-tick repellents and avoiding stagnant water helps.
🩺 Get annual heartworm tests. Even if your dog is on preventative meds, yearly blood tests can catch infections early before they become deadly.
Final Thoughts: Act Fast, Save a Life
Heartworms are deadly but preventable. If your dog is showing any of these symptoms, don’t wait—early detection is key to survival.
🚀 Take Action Today
✔ Book a vet appointment if you notice symptoms.
✔ Keep up with monthly preventatives.
✔ Spread awareness—heartworm disease is 100% preventable!
Got questions? Drop a comment or reach out! Your dog’s health is worth it.
