Heartworm Awareness Month: How to Prevent Cat Heartworm Disease

April is Heartworm Awareness Month, and we are happy to have an opportunity to spread awareness about this devastating yet completely preventable disease.

While heartworm disease is often associated with dogs, cats can be infected with heartworms, too. Contrary to dogs, though, cats are considered atypical hosts for heartworms because - luckily - most worms in cats do not survive to the adult stage.

According to the American Heartworm Society, “While this means heartworm disease often goes undiagnosed in cats, it’s important to understand that even immature worms cause real damage in the form of a condition known as heartworm associated respiratory disease (HARD). Moreover, the medication used to treat heartworm infections in dogs cannot be used in cats, so prevention is the only means of protecting cats from the effects of heartworm disease.” The AHS also found that heartworm continues to be diagnosed in all 50 states, so no one is immune to what they’re calling a “hearworm-demic”.

Because awareness and, most importantly, prevention of heartworm disease in cats is so critical, we’ve rounded up some frequently asked questions and answers about it.


What is cat heartworm disease?

Cat heartworm is an internal parasite that causes significant lung damage. Cats become infected by being bitten by mosquitoes. A mosquito injects these worms into the body of the cat, and it migrates toward the lungs.


Can a cat pass on heartworm to another cat, a dog, or a person?

No. All heartworms have pass through the mosquito for part of their life cycle before being transmitted to another animal.


What is the cycle of the heartworm in cats?

The heartworm cycle in a cat starts when a mosquito bites the cat and injects an immature worm into the cat’s skin. These worms then migrate through the skin into the bloodstream, months later arriving at the lungs. That's where the damage is done.

An infected cat develops an intense inflammatory reaction to destroy the worms present in the lungs before they continue to mature. Infected cats will have asthma-like symptoms—coughing, open mouth breathing, vomiting, and labored breathing. If the cat is lucky, the infection won't progress any further - their immune system will kill the immature worms.

It's important to remember, though: this initial immune response can cause significant medical issues for your cat, sometimes requiring hospitalization. Additionally, the lung damage may be permanent.

Sometimes a few worms will make it to adulthood in a cat. If so, that cat must live with the worm until it (the worm) dies. Supportive care is all that can be offered to the cat during this time, and, when the worm(s) die, the cat's immune reaction to the now-dead worm(s) can cause severe, sometimes life-threatening, health issues requiring hospitalization.


How does a cat's lifestyle affect their risk for heartworm?

Cats that spend time outside are at a bit of an elevated risk of becoming infected with heartworms, although anyplace where mosquitoes can be found poses a risk. 


What's a sign that my cat has heartworms?

Cats develop symptoms much earlier than dogs because cats' symptoms begin with immature worms in their lungs. Dogs' symptoms generally appear after worms have matured into adults. In reality, cats can experience symptoms ranging from absolutely none to sudden respiratory distress/collapse and death. Some symptoms are more common than others, though.


Signs that your cat may be infected with immature heartworms include:

  • Weight loss
  • HARD
  • Coughing
  • Labored breathing
  • Vomiting (cats tend to vomit with many different diseases)


Signs that your cat may be infected with mature heartworms include:

  • Vomiting
  • Labored breathing and coughing
  • Acute respiratory distress
  • Fluid in the belly
  • Shock
  • Death


Is heartworm painful for a cat?

Heartworm disease tends to cause asthma-like symptoms, so the cat can't breathe. Because the cat can't breathe, they tend to panic. Whether there's pain or not is unknown.


How is a cat tested for heartworm?

Diagnosing heartworms in cats typically requires both antigen and antibody tests. The antibody test looks for exposure to immature heartworms, while the antigen test looks for exposure to adult heartworms. However, x-rays and echocardiographs may also be needed to make a firm diagnosis.


Say my cat has tested positive for heartworm. What would the next step be?

If your cat’s tested positive for heartworm disease, the next steps would be X-rays, monitoring, symptomatic treatments, and bracing owners that this cat may go into a fatal crisis when the heartworm(s) die (they live about two years). 


How is heartworm prevented in cats?

We recommend monthly topical heartworm prevention medications - like Revolution Plus - to keep your cat from contracting heartworms. These prescription medicines prevent your cat from getting infected in the first place and, as we’ve mentioned, the key with a cat is to prevent them from getting infected.


How effective is heartworm prevention in cats?

Heartworm preventions are 95% or more effective if appropriately administered and given regularly.


Are there any holistic or over-the-counter treatments for heartworms?

There are not. Vector and mosquito control can help, but prescription preventative products are essential. Many of those preventative products also keep fleas and ticks away and help treat intestinal parasites.


Can I do anything in my cat's environment to reduce the risk of heartworm?

Heartworms are transmitted by mosquitoes, so anything you can do to reduce or eliminate them in your environment will help. Preventing standing water is essential. Additionally, you can use area mosquito sprays and the like, if they are safe for use around pets. 


What should I do if I miss a dose of my cat's heartworm prevention?

If you miss a dose, keep going. As soon as you realize you've missed it, go ahead and give the cat another one and go ahead with their regular monthly routine. 

If a cat does get an adult heartworm or two, there is no treatment available. They can't get the conventional treatment that dogs do as it's toxic to cats.  If infected, the cat develops chronic asthma-like symptoms, which may last for life. 


Are there side effects to the medications that we use in cats to prevent heartworms?

For the most part, these preventives are very well tolerated. Sometimes you’ll see local site reactions where you apply the topical. They may lose some hair and be a little itchy. On occasion, owners report that their cats don't feel well after they apply the topical. If you see other side effects, let us know, and we can help you determine the best product for your cat.


If you suspect your cat may have heartworm disease or you don’t have them on heartworm prevention, call us right away!


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