Heartworm disease in pets is a serious and potentially fatal condition. Having a clear understanding of heartworm disease will help you protect your dog and understand the signs, symptoms, and treatment options. Keep reading to learn more.


What Is Heartworm Disease?

Heartworm disease is a serious and potentially fatal health condition that can affect dogs, cats, and ferrets, as well as non-domestic species, such as wolves and foxes. If left untreated, heartworm disease can result in severe lung disease, heart failure, other organ damage, and even death. This disease is caused by a parasitic worm that can grow up to a foot long, known as Dirofilaria immitis. 

Dogs are the natural host for heartworms. It is caused by the introduction of larval heartworms into a dog’s bloodstream. Heartworm disease is not contagious between dogs; instead, a mosquito acts as the host and is needed to spread the disease. Heartworm disease can cause lasting damage to your dog’s heart, lungs and arteries, affecting your dog’s overall health and quality of life. 

Symptoms of Heartworm Disease in Dogs

In most cases, you may not notice symptoms of heartworm disease in your dog for months or even years after infection. By the time your dog begins to show signs of heartworm, advanced heartworm disease is usually already present and much of the damage is not reversible. Symptoms of dog heartworm disease, depending on the severity, can include: 

  • Coughing
  •  Fatigue
  • Intolerance to Exercise
  • Loss of Appetite
  • Weight Loss
  • Muscle Loss
  • Labored Breathing
  • Irregular Sounds in the Chest
  • Fainting
  • Weak Pulse
  • Bloated Stomach
  • Pale Gums
  • Dark, Bloody Urine

When these symptoms appear and the intensity of the symptoms usually depend on several factors, including how long the dog has been infected, the amount and the size of worms in the dog’s system, whether the dog lives an active lifestyle, and whether the dog has any prior health conditions. 

The Four Classes of Heartworm Disease

Class 1

  • Typically does not present any symptoms, or only presents minimal symptoms like occasional coughing.
  • This is the ideal time to diagnose and start treatment for heartworm disease.

Class 2

  • Presents with mild to moderate symptoms, such as tiredness after very little activity or an occasional cough.

Class 3

  • Symptoms are more noticeable to the pet owners, as the dog begins to appear sickly, with loss of weight and muscle. 
  • Generally will have a persistent cough and tiredness after minimal activity. 
  • Pet owners may also notice that their dog is showing signs of heart failure or having trouble breathing. 
  • Can be fatal if left untreated.

Class 4

  • In this class, it is called “caval syndrome”. 
  • By this stage, the heartworm population has risen so much that blood can no longer flow freely into the dog’s heart and brain. 
  • This is considered an emergency situation. Symptoms may include disorientation, collapse, labored breathing, pale gums, and dark-colored urine. 
  • Because most dogs cannot survive surgery at this stage, the main goal of treatment is to provide comfort for your pet. 

What You Can Do if Your Dog is Sick

With the safe and affordable heartworm prevention options today, no pet should ever have to endure this dreaded disease. By using a heartworm prevention product, such as Heartgard or Tri-Heart Plus, you can help to prevent your dog from contracting heartworm disease. Consult with your local veterinarian to determine which heartworm prevention program is best for your dog. 


If you notice any difference in your pet’s behavior or appearance or you just feel as though something isn’t quite right, schedule an appointment with your veterinarian today! Prompt medical attention can improve the outcome of many illnesses, not to mention help your dog feel better as quickly as possible. Our team of veterinary professionals at Bowman Road Animal Clinic is here to provide diagnosis and treatment if your cat is exhibiting any unusual behaviors. Contact our office today at 501-223-3737!