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Signs of Heartworm in Dogs

Signs of Heartworm in Dogs

What are the Signs of Heartworm in Dogs?

Heartworm disease is prevalent throughout the world. Every year in the United States, over 1 million dogs get heartworms.  It can be a silent killer for your dog. Animals may not show signs until the heartworm reaches maturity, which usually takes about six months.  Do you know which signs of heartworm parasites you should be on the look out for?

Signs of Heartworm in Dogs

Of course, prevention is the best way to protect your pet, but here are some signs of heartworm that you need to look for:

  • Dry, persistent cough:  The heartworm finds its way into the lungs and multiplying in the nearby veins, causing the dog to cough. A cough usually worsens after any exertion and may be accompanied by fainting. Fainting spells are common in dogs with heartworms, as the parasite affects their breathing.
  • Chronic tiredness or lethargy:  Your usually energetic pup has become tired and won’t get up to play or even take a walk. Even the smallest bit of exercise leaves him exhausted. You just don’t see the same healthy spark in your pet anymore.
  • Sudden loss of appetite or weight:  Even dogs with generally very healthy eating habits will show signs of not wanting to eat.  This happens because the heartworms are slowly taking over his body. They will not want to eat and get noticeably thinner. Dogs will even refuse their favorite treats, which is a clear indicator that something is not right with their health.
  • Difficulty in breathing:  Heartworms cause pets to have trouble breathing which could include increased panting or a fast heart rate. This is attributed to the parasites invading the hearts and lungs, choking off oxygen in the blood. You may notice your animal becomes out of breath with the slightest exertion.
  • Bloated chest or stomach:  As heartworms mature and increase in your dog’s body, he may take on the appearance of a bulging chest or stomach. This symptom is enhanced because of the weight loss your dog is suffering.  Fluid increase is also a potential cause, which makes the animal’s stomach bigger. His chest or stomach will be noticeably distended.
  • Unusual allergies:  As heartworms increase in your pet’s body, parasitic offspring will become a factor. The dog may exhibit allergic reactions to things that previously did not affect him. Asthma and other respiratory illnesses may develop.
  • Complete collapses:  As more and more heartworms invade your dog’s body, different systems and organs begin to fail. Blood flow can be blocked, and the animal will go into shock and then just a complete collapse. This is a critical health issue, and death could follow this stage.

Less Common Signs of Heartworm Parasites

Moreover, if the heartworms travel to other parts of the body besides the lungs and heart, the dog can exhibit other less common symptoms such as lameness, blindness, seizures, excessive sleeping, and nosebleeds. Finally, the only way to positively identify heartworms in your pet is have your veterinarian perform a heart-worm blood test.

It is critical to catch heartworms as early as possible.  So, if you detect any of the signs of heartworm mentioned above, you should make an appointment with a vet, as soon as possible. In short, it could mean the difference between life and death for your pet.


(The image above is a derivative of Austin Community College,; CC BY-SA.)

Heartworm Treatments