As a pet owner, you’ve no doubt heard of heartworm disease, but you may not know a lot about it. This parasitic disease can prove fatal to pets, so knowing the ins and outs of heartworm disease is essential for keeping your four-legged friend safe from infection. To help you learn everything about heartworm disease, from transmission to prevention, our Red Oak Animal Hospital team has put together a comprehensive guide for pet owners.

What causes heartworm disease in pets?

Heartworm disease is caused by an infected mosquito that bites and transmits heartworm larvae to your pet. These larvae (i.e., microfilariae) enter your pet’s body and make their way to the blood vessels surrounding the heart and lungs, often in large enough numbers to infiltrate these vital organs.

As the microfilariae migrate from the mosquito’s bite wound to your pet’s pulmonary artery, they create untold scarring and permanent damage to bodily tissues and vasculature. After about six months, the larvae reach adulthood and begin reproducing, causing more destruction in your pet’s circulatory system and generating a new microfilaria population that will infect mosquitoes that bite your pet.

Can all pets get heartworm disease?

Any mammal, including cats and people, can contract heartworm disease, although the parasites prefer canines as hosts. Additionally, since mosquitoes can easily slip inside your home, indoor-only cats are not safe, so all pets should be on heartworm prevention year round.

Can I tell if my pet has heartworm disease?

Heartworm disease is a slow-growing condition that can take months before  your pet shows obvious signs. In fact, you will not likely notice that your pet has heartworm disease, especially if you adhere to the American Heartworm Society’s guidelines concerning annual testing. 

However, if heartworm disease progresses in your dog, you may notice the following signs:

  • A mild, persistent cough
  • Reluctance to exercise
  • Fatigue after moderate activity
  • Decreased appetite
  • Weight loss

Then, as the disease advances to more severe stages, your dog may develop heart failure, and you will see that their abdomen is swollen with backed-up fluid. Dogs can also develop a sudden blood flow blockage in the heart that can cause labored breathing, pale gums, or coffee-colored urine. Without prompt surgical removal of the blockage, few dogs survive.

Detecting heartworm disease in cats through clinical signs alone is also difficult, as the signs can be vague, subtle, or dramatic. Cats with heartworm disease may:

  • Cough
  • Have asthma-like attacks
  • Vomit
  • Lose weight
  • Exhibit a lack of appetite
  • Have difficulty walking
  • Experience fainting or seizures

Unfortunately, sometimes the first—and only—sign in cats is sudden collapse or death.

How is heartworm disease diagnosed?

Heartworm disease can be diagnosed only via a blood test that can detect heartworm proteins, or antigens produced by adult female heartworms. If the heartworms are immature, all male, or too few, the result will be a false negative. Because of these false results, annual testing is critical to ensure disease is not brewing undiagnosed. 

How is heartworm disease treated in dogs?

For a dog who has tested positive for heartworm disease and has a confirmed diagnosis after additional testing, a typical treatment plan includes:

  • Exercise restriction — Physical activity increases the speed of the heartworms’ damage to the heart and lungs, so exercise restriction is critical from the time of diagnosis to six to eight weeks following treatment.
  • Disease stabilization — If the disease is severe, or your pet has other health issues, your pet’s condition may need stabilizing before we proceed with treatment.
  • Treatment administration — A series of arsenic-based injections are administered into your dog’s lumbar muscles and can cause discomfort and nausea, and make your pet feel ill. 
  • Follow-up care — After treatment that kills the adult heartworms has been administered, testing for microfilariae and heartworm antigen is necessary, and will guide the course of additional treatment.

How is heartworm disease treated in cats?

While the treatment process for dogs with heartworm disease is a long and complex process, no treatment is available for cats. The medication used to eradicate adult heartworms in dogs is not approved for use in cats with heartworm disease, and they must be given supportive nursing care based on their clinical signs.

How can I prevent my pet from developing heartworm disease?

Although heartworm can be a deadly disease, prevention is simple. We offer many products for purchase at our hospital and through our online pharmacy, and we are happy to discuss all the prevention options, including a variety of oral tablets and chews, topical applications, and injections. Depending on your pet’s needs and preferences, their heartworm preventive may also offer protection against fleas, ticks, intestinal worms, and mange mites.  

If you are unsure about choosing the right heartworm preventive, contact our Red Oaks Animal Hospital team. We will discuss all your options and ensure you purchase the product best for your pet.