Signs of Feline Heartworm Disease

Signs of Feline Heartworm Disease

Heartgard for Cats

Heartworm & Deworming
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Are you shocked to find out that cats are susceptible to contracting heartworm disease just like dogs? Learn more here.

A heartworm is a parasite that travels from one host’s blood to the next host via mosquito bites. Though heartworm disease occurs less frequently in cats than dogs, and when it does, cats typically have a smaller number of heartworms present than dogs. And even though the parasite’s life cycle is shorter in cats. felines are still susceptible to it, meaning that putting your cat on heartworm medication, like Heartgard for Cats, is still worth considering.

Symptoms of Feline Heartworm Disease

Because heartworm is less common in cats, the symptoms of this disease are often misdiagnosed as respiratory problems. Signs of heartworm typically show up when the larvae enter the lungs and when adult heartworms die.

Common symptoms of heartworm include:

  • Difficulty breathing (i.e. wheezing, panting)
  • Asthma-like symptoms
  • Coughing
  • Vomiting
  • Lethargy
  • Weight Loss
  • Diarrhea
  • Shock
  • Sudden Death

Some cats do not show any signs of illness and may die suddenly if a heartworm blocks the arteries and obstructs blood flow to the lungs.

Diagnosing Feline Heartworm Disease

Feline heartworm disease is more difficult to diagnose, and testing for this parasite in cats is not always reliable. Common blood tests often reveal false negatives, so a series of tests is usually administered.

Along with a physical exam, imaging and blood tests for heartworm that your vet may perform include:

Antigen tests

This test detects heartworm antigens in the blood, but is limited to signalling the antigens of adult female heartworms (and in some cases, dying male worms) in cats. Immature heartworms under seven months old and male heartworms will go undetected, so this test can produce false negatives.

Antibody tests

This blood test monitors a cat’s immune response to heartworms by detecting antibodies produced by the cat. Cats that are both currently and previously infected will test positive for antibodies, so a positive test result can indicate past infection of heartworm disease that has been cleared up.


An echocardiogram is an ultrasound reading of the heart and main pulmonary artery that can detect the presence of heartworms. Heartworms that are seen in ultrasounds confirm diagnosis. However, this test does not cover all the pulmonary arteries where heartworms are frequently found, so negative results do not rule out infection.


X-ray imaging of the heart and lungs detects signs of an infection, typically seen as enlarged and irregular pulmonary arteries.

Microfilarial tests

Microfilarial tests detect the presence of microfilaria in the blood, but negative test results would not rule out an infection. Microfilariae are not present during the adult stages of heartworm, and since cats tend to have one or two heartworms, mating worms that produce microfilariae are less common. If microfilariae are detected, however, it is a clear confirmation that the disease is present.

As you can see, while cats are less likely to contract heartworm, the disease can still have a very negative impact on our feline friends. That’s why it’s important you give your pet preventative medicine to keep them healthy and heartworm-free.

Related Content

Heartworm Disease in Dogs: 5 Things You Should Know
Heartworm Symptoms
How to Prevent Heartworm in Dogs

This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by,your veterinarian. Always seek the advice of your veterinarian or other qualified professional with any questions you may have regarding a medical condition. Never disregard or delay seeking professional advice due to what you may have read on our website.

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