Potential Complications of Heartworms in Cats

The symptoms of heartworm in cats can quickly progress — and the side effects could be fatal. Learn how to prevent heartworms in cats.

Heartworms are parasites that cause damage to both the heart and lungs of cats. Mosquitoes carry these small larval worms and when an infected mosquito bites your cat, the worms often migrate to the lungs where they trigger an inflammatory reaction.

While this typically kills most of the worms, it can cause lung damage and respiratory distress and can even be fatal. While cats are less likely than dogs to have large adult worms in their heart and lungs, if worms do survive and reach the cat's heart, there is no approved treatment.

Vet examining a tabby cat with a stethoscope.

What are the symptoms of heartworms in cats?

Despite the name, heartworm in cats is actually considered a disease of the lungs more so than the heart. Because of this, symptoms are often associated with the respiratory system, including:

  • coughing
  • increased respiratory effort
  • quick shallow breaths
  • wheezing

Other symptoms include:

  • vomiting
  • lethargy
  • seizures

If your cat displays any of these symptoms, talk to your vet about testing them for heartworm disease.

What could be the long-term complications of heartworm disease in cats?

If your cat is infected with heartworms, they may experience serious issues such as blood clots, respiratory disease, and permanent lung damage. Steroid treatments may help, but cats with more serious heartworm disease may require IV fluids, antibiotics, drugs and even supplemental oxygen as their lungs may not be functioning well.

Can heartworm be cured in cats?

Unfortunately, there is no cure for heartworms in cats. The medication used to kill heartworms in dogs is not safe or approved for use in cats. Because of this, preventing heartworms in cats is essential.

How can heartworms be prevented in cats?

Keeping your cat indoors helps lower the chance of heartworm infection, but both indoor and outdoor cats are still at risk of contracting heartworm disease since mosquitoes frequently make their way indoors.

To prevent heartworms in cats, pet owners should give them a monthly preventive. Whether topical or chewable, all heartworm preventives work to get rid of larval heartworms in the pet left by a mosquito. This keeps larval heartworms from developing into older heartworms that can cause heartworm disease in cats. It's important to give your pet heartworm preventives on schedule — setting an alert on your phone is an easy way to remind yourself.

Heartworm disease is more common in cats than people realize and if your cat does become infected, it can be fatal. Protecting your cat from heartworm infection by using a monthly preventive is easy and could save their life.

Related articles:
Intestinal Worms in Cats
How to Give a Cat a Pill

Bayer Products

  • Advantage Multi® for Cats (imidacloprid + moxidectin) packaging

    Advantage Multi® for Cats (imidacloprid + moxidectin)

    An all-in-one monthly topical that prevents heartworm disease, kills adult fleas and treats roundworms and hookworms.

    Advantage Multi® for Cats (imidacloprid + moxidectin)

    Indicated for:


    CAUTION: Federal (U.S.A) law restricts Advantage Multi® for Cats (imidacloprid + moxidectin) to use by or on the order of a licensed veterinarian.

CAUTION: Federal (U.S.A.) law restricts Advantage Multi® for Cats (imidacloprid + moxidectin) to use by or on the order of a licensed veterinarian. WARNINGS: Do not use on sick or debilitated cats or ferrets. Do not use on underweight cats. (see ADVERSE REACTIONS). Do not use on cats less than 9 weeks of age or less than 2 lbs body weight. PRECAUTIONS: Avoid oral ingestion. HUMAN WARNINGS: Children should not come in contact with the application site for 30 minutes after application.