Heartworm In Cats: Causes, Symptoms, Prevention, & Treatment

Heartworm disease is most common in dogs, but it can appear in cats along with more than 30 other species of animals, including humans — though it’s rare.

While the disease can appear in cats, it’s different than the way it appears in dogs. Most heartworms don’t survive until adulthood in cats, and affected cats usually have only one to three adult heartworms if not zero.

This may seem like a good thing, but it does make heartworm disease difficult to diagnose in cats, and even heartworms that aren’t fully grown can cause a condition called heartworm associated respiratory disease.

It’s important to know the causes and symptoms of heartworm disease, as well as means of prevention to keep your cat safe.

Causes Of Heartworm In Cats

Mosquito on Cats nose
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Heartworms are spread by mosquitoes. They carry the larvae from a host infected with adult female heartworms, which produce microscopic babies called microfilaria that move through the bloodstream.

The mosquito carries the microfilaria as they develop to the infective stage over ten to 14 days. Then, the infective larvae are deposited on a new host’s skin and enter the bloodstream of the animal through the wound created by the mosquito bite.

Over the next six months, the larvae can grow into adult heartworms. Adults have a lifespan of two to three years in cats.

Symptoms Of Heartworm In Cats

Candid picture of my cat Boris yawning/coughing up a furball.
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The symptoms of heartworm disease in cats range from mild to severe. They can include:

  • Coughing
  • Raspy breathing known as dyspnea
  • Asthma-like attacks
  • Vomiting
  • Weight loss
  • Lack of appetite

Respiratory issues and vomiting are the most common signs in cats with chronic infestation.

Cats with heartworm may also develop a heart murmur or irregular heartbeat rhythm. Some cats may have difficulty walking or suffer from fainting or seizures.

Sometimes there are no symptoms, and the only sign is sudden collapse or even death.

Prevention Of Heartworm In Cats

Doctor veterinarian examining beautiful adult cat
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Preventative heartworm medication can be given to cats in the form of an injection, a pill, or a topical treatment. These medications work by killing off heartworms in the larval stage.

Typically, the oral and topical treatments are recommended to be administered monthly, while the injection is usually given every six months.

It’s important to stay on schedule with the medication because it only takes as little as 51 days for heartworms to mature into adulthood, and they must be killed in the larval stage. Preventative medication does not affect adult heartworms.

Diagnosis & Treatments For Heartworm In Cats

Vet examining a cat's x-ray
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As mentioned before, heartworm disease is different in cats than it is in dogs. There is no specific test for the disease in cats.

Instead, your veterinarian can perform a variety of tests to rule out other conditions and determine if heartworm disease is the cause of your cat’s symptoms.

These tests include urinary analysis, antigen and antibody tests, x-rays to find enlarged veins and arteries that indicate heartworm disease, or an electrocardiograph which can identify heartworms in the heart along with revealing other heart diseases that can show similar symptoms to infestation.

There is no drug that can kill adult heartworms in cats, which is why prevention is so important.

Your vet may suggest a surgical procedure to remove adult heartworms, but because heartworms have a fairly short lifespan in cats, your vet might recommend that you stabilize and monitor your cat as they fight off the infection naturally.

Many cats produce enough antibodies to fight off heartworm infection on their own.

Veterinary examining a Scottish Fold Cat
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You will need to develop a long-term management plan for your cat, which will include follow-up visits to your vet. Your vet may give you medication to continue management of mild symptoms in your cat, including steroids or prednisolone to reduce inflammation.

For more severe infections, your cat may need intravenous fluids, drugs for lung and heart issues, antibiotics, or nursing care.

If your cat fights off the heartworm infection and recovers, it’s important that you continue preventative care. Cats who’ve been infected are already susceptible, and you don’t want your cat to beat the condition just to get infected all over again.

Do you keep up with heartworm disease prevention? Has your cat ever fought off a heartworm infection? Let us know in the comments below!

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