Does My Cat Have Heartworm? Signs, Treatment, Prevention

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

Brittany Leitner

Updated December 16, 2022 • Published June 25, 2021

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Does My Cat Have Heartworm? Signs, Treatment, Prevention

Heartworm is one of those awful diseases that actually affects both cats and dogs equally. And yes, it really does refer to a parasitic worm making its way into your pet’s organs and wreaking havoc on their overall health.

Heartworm in cats is not a disease to be taken lightly. In fact, if left untreated it can be fatal, as it progresses over time and gets worse the longer it goes untreated. If you’re a new cat owner or just want to make sure you’re looking after your pet as best as possible, Catherine Lenox, DVM, DACVN and regulatory veterinary manager at Royal Canin, breaks down what you need to know about preventing heartworm in your cat.

What is heartworm in cats?

"Heartworm disease is caused by a worm that can live in the blood vessels, heart, and lungs of cats and dogs,” explains Dr. Lenox. However, it does manifest differently in dogs vs. cats. “Cats have fewer worms with a heartworm infection, but are often more susceptible to showing signs than dogs, so they may have more severe disease,” she says. These are some of the most dangerous cat parasites.

How does a cat get heartworm?

Heartworms are caught by mosquito bites. But “it’s important to note that a mosquito bite can occur any time during the year, and even indoor cats are susceptible to getting mosquito bites,” says Dr. Lenox. “Many people think that their indoor cats are not at risk, but all cats are at risk, even those that live indoors. A mosquito can easily sneak inside without you knowing when you have the door open.”

Is heartworm contagious?

Heartworm can only be transmitted through mosquitos who are carriers. “So if you have a pet that has heartworm disease, your other pets are not at more risk even though they live in the same household,” says Dr. Lenox. 

All breeds of cats are also equally susceptible to heartworm, the same as all dog breeds are. “Heartworm disease in cats is more common in hot areas with a high mosquito population, but cats in all areas can be infected,” says Dr. Lenox. 

Signs your cat has heartworm

 A cat will show signs of heartworm quicker than dogs do. “The most common thing that can happen with cats that have heartworm disease is sudden collapse,” says Dr. Lenox. “They may be acting fine, have sudden and severe problems.” Other symptoms may include:

  • Asthma-like signs

  • Coughing

  • Vomiting

  • Loss of appetite

How heartworm in cats affects life expectancy

Heartworm is progressive, so it can impact a cat or dog more severely if it is caught later. “If the disease is caught on routine testing, and there are no signs at the time of detection, it may be possible to treat the disease. However, many cats may have lifelong breathing or heart difficulties,” says Dr. Lenox.

How to diagnose heartworm in cats

The only way to truly diagnose heartworm is through a blood test at the vet’s office.

How to treat heartworm in cats

Although Dr. Lenox says heartworm can be difficult to treat, it’s important to remember that heartworm is preventable. Talk to a vet as soon as possible about a health plan for your cat, including which medications are recommended to prevent the disease. Preventing it before it starts is the best way to “treat” heartworm. Otherwise, depending on the stage of the heartworm progression, treatment plans may vary.

 How to prevent heartworm in cats

“There are a lot of different prevention products that your veterinarian can prescribe,” says Dr. Lenox. “Some of these products also help prevent intestinal parasites. For cat heartworm prevention, ensure that the product is specifically labeled for use in cats.” Otherwise, heartworm medications labeled for dogs can cause serious health problems for your cat.

You can try collars, which cannot prevent heartworms but they can keep fleas and ticks off of your cat so they are more comfortable. You can also try drops: You can remove tapeworms and roundworms with an over the counter drop, but heartworm can only be removed in-office.

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