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The veterinary profession has done an outstanding job educating dog owners about the danger of heartworm infection in dogs. We have not done a similar job educating cat owners about this risk. Nationwide approximately 59% of pet dogs are being protected by the use of heartworm preventatives, while only 5% of pet cats receive preventative medication. Why is there such a disparity?

Heartworm disease in cats is not a new phenomenon, but it has been misunderstood and under-diagnosed for decades. Heartworm was first recognized in dogs, which are its natural host. The parasite successfully completes its life cycle within the chambers of the dog’s heart leading to the classic symptoms of congestive heart failure. Cats are exposed to heartworm infection from the bite of a mosquito just as dogs are, but because they are not a natural host to the parasite cats develop a different disease pattern.  Cats instead develop an often fatal respiratory condition referred to as H.A.R.D. or Heartworm Associated Respiratory Disease. The symptoms of H.A.R.D. are insidious and can include: weight loss, vomiting, rapid breathing, gagging, coughing, wheezing and sudden death. In the past, many affected cats were thought to have Feline asthma or bronchitis.

Another factor in the under-diagnosis of Feline Heartworm Disease is the complexity of testing for the condition. We have a straight forward, reliable test for dogs but the diagnosis in cats usually requires a number of tests, chest radiographs and sometimes an ultrasound study for confirmation. Screening tests at our hospital revealed that 13% of the feline patients tested had been exposed to heartworm. Similar findings were reported in a survey of this area conducted by the American Heartworm Society.

Many cat owners mistakenly believe that their cats are protected from heartworms because they live indoors. All of us in this geographic area have been bitten by mosquitoes in our homes and it only takes the bite of one infected mosquito to transmit heartworm to your cat. A study in North Carolina revealed that almost 30%
of cats diagnosed with heartworm disease were indoor only cats.

Clearly prevention is the key to protecting our cats. The Association of Feline Practitioners and the American Heartworm Society strongly urge that all cats receive monthly doses of heartworm protection.  Safe and effective monthly preventative medications are available from your veterinarian.

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