Cats Can and DO Get Heartworm - So Protect Your Cat
Drs. Foster & Smith Educational Staff

Heartworm disease, caused by the parasite Dirofilaria immitis, affects cats in every U.S. state. Because heartworm disease is difficult to diagnose in cats, the exact number of infected cats is unknown.

Many people falsely believe that cats cannot get heartworms because cats tend to live indoors. Unfortunately, mosquitoes – the heartworm vector – can easily come indoors.

Mosquitoes often carry heartworm larvae. When a mosquito bites your cat, the larvae enter her skin. Without preventive medication to stop them, the larvae migrate to the heart, where they grow into adults up to 5 inches long. Infected cats usually host 1-4 worms that can live up to 2 years.

In cats, adult heartworms and heartworm larvae actually damage the respiratory system much more than they do the heart; immature worms pass from the heart into the blood vessels leading to the lungs. Here, most of them die and cause acute inflammation. This condition is called "Heartworm Associated Respiratory Disease" or "HARD."

Many cats with HARD will show no signs of disease, despite having severe lung damage. Other cats will exhibit:
Coughing Difficulty breathing Listlessness
Appetite loss Weight loss Vomiting
Rapid heart rate Fainting Blindness
Collapse Convulsions Sudden death

First and foremost, protect your cat with a prescription heartworm preventive. Give it year-round even if mosquitoes are seasonal in your area; this can stop heartworms from developing into adults and protect against intestinal parasites.

Additionally, limit your cat’s exposure to mosquitoes. Keep her indoors whenever possible, shut exterior doors, and repair damaged window screens. If your cat enjoys the outdoors, supplement her heartworm preventive with a mosquito repellent such as Bio Spot for Cats, eliminate any nearby standing water, and place mosquito traps in your yard.

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