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By Dr. Heather Markway
Published: April 19, 2012

Most pet owners are familiar with the risk and need for heartworm prevention in dogs, but our beloved cats can contract the disease as well. Unfortunately, cats are often at higher risk for a more severe response and outcome once they are infected. Although outdoor cats are at greater risk of being infected, a relatively high percentage of cats considered by their owners to be totally indoor pets also become infected.

Heartworm infection takes place when a mosquito carrying infective, microscopic-size heartworm larvae, bites into a cat for a blood meal. The larvae then actively travel through the cat's body, eventually settling into the arteries and blood vessels of the lungs, where they continue to develop to become mature, 6-12 inch long worms.

Even though cats usually have fewer numbers of heartworms compared to dogs, they tend to have a more intense immune response. Undetected feline heartworm infections can have fairly non-specific clinical presentation such as vomiting, inappetance, anorexia, and weight loss, but cats can present with more severe clinical signs such as asthmatic-like cough, panting, gagging, difficulty breathing, or even sudden death.

Diagnosis can be difficult due to the lower number of worms present in feline heartworm disease, but physical exam, blood testing, and radiographs (x-rays) can help determine your cat’s heartworm status. Unfortunately, once a cat is diagnosed with heartworms, there is no approved medication to treat the disease in cats, so prevention is the key to keeping your cat from becoming infected. A monthly oral or topical prevention that is given year round can prevent the potential fatal disease from affecting your beloved cat.