What Are the Signs of Heartworm in Dogs?

What Is Heartworm?

Heartworm disease is a potentially fatal condition caused by parasitic worms (Dirofilaria immitis) living in the heart, lungs, and blood vessels of dogs. It’s spread by mosquitoes, making it a real threat in many climates. Left untreated, it can cause severe lung disease, heart failure, and even death.

How Dogs Get Infected

Mosquitoes are the villains here. When a mosquito bites an infected animal, it picks up microscopic baby worms. Then, it transmits them to your dog during the next bite. Over time, these larvae grow into foot-long adult worms and start clogging up your dog’s heart and lungs. Yikes, right?

Early Warning Signs of Heartworm

Spotting heartworm early is tough because the symptoms creep up slowly. But catching them early can save your dog’s life.

Mild Coughing

A persistent, dry cough is one of the first signs. It’s often mistaken for kennel cough or allergies. But if it doesn’t go away—take note.

Fatigue After Mild Activity

Does your pup seem worn out after a short walk or playtime? That’s a red flag. Heartworms put stress on the heart, making normal activities exhausting.

Loss of Appetite

This one's tricky because dogs can skip meals for many reasons. But if it's paired with other symptoms? Don’t ignore it.

Progressive Symptoms of Heartworm

As the disease progresses, signs become harder to miss.

Labored Breathing

Your dog may breathe heavily or rapidly, even while resting. That’s due to inflammation and damage in the lungs from the worms.

Swollen Belly (Due to Fluid Buildup)

A bloated abdomen can be a sign of fluid accumulation—a result of heart failure. It’s often seen in later stages of infection.

Sudden Weight Loss

Dogs battling heartworm may shed pounds rapidly. Their bodies are working overtime to fight off the infection. Check out the best heartworm treatment for dogs!

Advanced Stage Heartworm Symptoms

At this point, heartworms have done serious damage.

Fainting or Collapse

Heartworms interfere with blood flow, which can lead to sudden collapses. Some dogs even faint after light exercise.

Nosebleeds or Blood in Urine

Bleeding issues can arise as the body becomes weaker and organs start to malfunction.

Caval Syndrome (Emergency!)

This is a life-threatening complication where heartworms block blood flow. Symptoms include dark urine, collapse, and severe lethargy. Emergency surgery is the only option—and even then, survival isn’t guaranteed.

How Vets Diagnose Heartworm in Dogs

Early detection is key, and thankfully, vets have reliable tools.

Blood Tests

Simple bloodwork can reveal heartworm antigens or microfilariae (baby worms). This is the most common test during routine checkups.

Chest X-rays and Ultrasounds

These help assess the severity of infection and determine whether organs like the lungs or heart have sustained damage.

Importance of Early Detection

Why You Shouldn't Wait for Symptoms

The earlier you catch it, the better the outcome. By the time symptoms show, damage is already underway.

Role of Routine Vet Checkups

Annual vet visits and heartworm tests are essential—even if your dog looks perfectly healthy.

Heartworm Treatment for Dogs

Can It Be Cured?

Yes, but it's not easy or cheap. Treatment can be tough on dogs and requires strict rest, but it can save their life.

Medication and Injection Protocol

Most dogs receive a series of injections to kill adult worms, along with antibiotics and steroids to handle inflammation. Some may also need meds to kill larvae first.

Post-Treatment Recovery and Care

Here’s the hard part: your dog will need to rest—like, really rest. Running or jumping can cause dying worms to break off and block vessels. Crate rest becomes your best friend.

Conclusion

Heartworm disease is sneaky, dangerous, and potentially fatal—but it’s also 100% preventable. If you notice any of the signs we covered, act fast. Whether it's a light cough or a bloated belly, early action can save your dog’s life. Stay consistent with heartworm prevention, schedule annual tests, and never skip a dose. Because when it comes to heartworm, it’s not worth the risk.

FAQs

1. Can heartworm kill a dog?

Yes, if left untreated, heartworm can lead to heart failure and death. Early detection and treatment are key.

2. How long does heartworm treatment for dogs take?

Typically, the full course lasts several months, including pre-treatment, injections, and post-treatment recovery.

3. Is heartworm contagious between pets?

No, heartworm is not spread directly between pets—it requires a mosquito as the carrier.

4. Are there natural remedies for heartworm?

While some claim natural alternatives work, none are scientifically proven or vet-approved. Stick with what’s safe and effective.

5. How expensive is heartworm treatment for dogs?

Costs vary, but treatment can range from $500 to $1,500 depending on severity. Prevention, by comparison, is much cheaper!