Does My Cat Have Heartworm? Signs, Treatment & Prevention

Heartworm in cats is a terrible disease. Learn more about the signs, treatments, and prevention of heartworm in cats to better protect your pet.

Brittany Leitner

Updated May 19, 2023 • Published June 25, 2021

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Does My Cat Have Heartworm? Signs, Treatment & Prevention

Heartworm in cats is not a disease to be taken lightly. Heartworms are caused by parasitic worms that make their way into your pet’s flesh via a mosquito bite and is a serious disease that can cause health complications if left untreated.

Luckily, there are ways to treat heartworm infection if it’s detected early enough by your veterinarian.

Read on to learn what heartworm is, the signs your cat has heartworm, and how the disease can be treated and prevented.

What is heartworm in cats?

Heartworm disease is a preventable illness that cats contract when a mosquito carrying the heartworm larvae bites their skin. Once bitten, the larvae progress through various stages and migrate within the cat's tissues until they reach the heart and lungs. The amount of female worms that mature into the adult stage will determine the number of worms that live and reproduce in the body.

Unlike dogs, just a few worms in a cat’s heart can cause signs of illness. The adult heartworm will grow to its full potential no matter if it is growing in a 7-pound cat or a 70-pound dog.

Signs your cat has heartworm

Unlike dogs who will start showing signs of infection and usually give their pet parent a chance to have them treated, cats typically seem completely healthy until they suddenly collapse.

Signs that your cat may exhibit, but usually do not appear before collapse, include:

As the number of worms increase, they cause damage to the heart and prevent blood from properly pumping into organs and tissues. Once a cat is exhibiting signs of the disease, the resulting damage to the heart can be irreversible and dramatically shorten the cat's lifespan.

How to prevent and treat heartworms in cats

Ensuring your cat is protected against heartworm infection is vital—consult your veterinarian to discuss the best preventative medication. In the unfortunate event that your cat tests positive for heartworm disease, treatment can be started, but treating cats with this infection comes with a lot of complications.

Giving your cat monthly oral or topical preventatives effectively deworms your cat for specific heartworm larval stages. Consistency is key, as each month without medication leaves your cat vulnerable to larvae transmitted by infected mosquitoes. By following a regular preventative schedule, you can ensure all stages that are susceptible to the ingredients in the medication are killed. Plus, these preventatives also address intestinal parasites.

You can decrease the mosquito burden in your backyard by using mosquito repellants, but there are no guarantees that your cat will not be bitten by an infected mosquito.

The truth about heartworm infection

Dispelling misconceptions about heartworm infection in cats is crucial to make sure our feline friends are covered.

Some believe that strictly indoor cats are safe without prevention since they don't venture outdoors. However, mosquitoes can easily enter your home and bite your cat.

Another misconception is that cats living in areas that don't have heartworm-carrying mosquitoes don't need to take preventive measures. This is false, as positive cases have been reported in all 50 states.

Despite some pet parents not providing heartworm prevention and avoiding infection, the increased cat travel across regions and transportation of rescue cats from high-risk areas significantly increases the chances of transmission. While's it's true that heartworm larvae is transmitted through an infected mosquito, the scary part is that when a mosquito bites a cat that is infected with heartworms, they carry that larvae in their mouth and are now able to infect other cats.

If your cat is not on monthly preventative medication, it's never too late to have them tested and start prevention. Consult your veterinarian or the experts at Pawp to determine the best approach for your cat.


Reviewed and fact-checked by

Mika, RVT at Pawp

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