Understanding Heartworm Disease in Cats

Tortoiseshell_she-catMany decades ago, veterinarians didn’t really know the significance of heartworm disease in cats. It turns out that cats are about as likely to be affected by the disease as dogs - though the disease is totally different in cats.

“Different doesn’t mean less significant,” Dr. Stephen Jones, president of the American Heartworm Society says,

So, here’s the deal – it’s a bad day for a little heartworm guy who winds up inside a cat as a result of a mosquito bite. But mosquitoes aren’t picky and will as cheerfully bite cats as they do dogs or for that matter, people. The cat is generally an end host for heartworm. However, that doesn’t mean the disease is any less a problem for cats than it is for dogs – it’s just different.

One symptom of heartworm in cats is sudden death. Heartworm is the number two cause of sudden death in cats (behind feline hypertrophic cardiomyopathy, a kind of heart disease characterized by thickening of the heart muscle). Still, no one knows exactly how many cats suddenly die of heartworm since most owners don’t agree to a necropsy (animal autopsy) to determine cause of death.

Jones says it’s only recently that researchers discovered that many cats with asthma-like symptoms are actually suffering from a heartworm induced condition called heartworm associated respiratory disease (HARD). While the disease can be managed, there’s a financial cost to owners and a quality of life cost to the cats unlucky enough to have it.

Some heartworm positive cats have less significant issues, such as frequent vomiting – which owners, perhaps even veterinary professionals, mistake for typical cat hairballs. Other non-specific signs might be a chronic cough and/or lethargy. Other cats offer no symptoms. Either these cats are masking illness, as cats can effectively do, or they really and truly have no symptoms and feel great.

Typically cats don’t suffer the potentially large heartworm load that dogs might, which may easily exceed a dozen worms, or even dozens. For cats one worm may be typical. But recent research suggest one worm is enough to cause permanent damage.

“We can’t easily test for heartworm infection in cats, and we cannot treat it – but since we can prevent it, that is the best wellness care recommendation we can make,” says Dr. Colleen Currigan, president of the American Association of Feline Practitioners.

But are veterinarians and veterinary technicians doing enough to support prevention?

The data tells the story, or at least a part of the story. Over half of all dog owners walk out of a vet clinic without heartworm prevention. Jones says he has no idea how many cat owners walk out without heartworm protection, but likely that number is far closer to 100 percent than 50 percent.

Jones, who is in Monks Corner, SC, adds that since cats aren’t as likely to see veterinarians for preventive care or check ups compared to dogs they may have a very specific reason for being there. Perhaps the cat suffered an injury or is being diagnosed with diabetes or even cancer. So, at least the perception is that abruptly bringing up the topic of heartworm might not be well received.

Since other cats may not even visit the veterinarian, it’s obviously quite the challenge for veterinarians or veterinary technicians to deliver messages to clients they’re not seeing.

Perhaps the biggest issue from cat owners is the indoor cat defense, which has at least some validity, and makes sense if the cat is truly indoors and the cat owner is on the 45th floor of a high rise. But then again, Currigan seeks an explanation for indoor only cats – even in the heart of Chicago where she practices – who get heartworm. There is only one way to get heartworm disease, and that is from the bite of a mosquito.

Also, some people say they keep their cats indoors – but the definition of indoors might include a porch that isn’t quite mosquito proof or include a backyard which is anything but mosquito proof.

Some veterinarians are so happy to see cat clients; they don’t want to push the envelope or assume that Mrs. Smith won’t pay for heartworm protection for her cat because she never has before or doesn’t seem to have the money.

“While I understand and sympathize with these explanations, we’re not serving the pets or clients best interest if we don’t talk about heartworm,” Jones adds.

Finances may of course be an issue for many pet owners, the cost of heartworm prevention. Veterinarians are well trained, and totally correct to point out that in dogs treatment for heartworm is often difficult on the dogs, and so expensive that it will far exceed the cost of prevention. In cats, there is no treatment. Arguably, prevention in cats is as priceless as the cats themselves.

©Steve Dale

Steve Dale, CABC is a certified animal behavior consultant, and co-editor of “Decoding Your Dog,” (authored by the American College of Veterinary Behaviorists) and author of ebooks “Good Dog” and “Good Cats.” His host of two national radio shows, and is heard on WGN Radio Chicago. And he severs on Boards, including the Winn Feline Foundation and Tree House Humane Society, Chicago. His blog: www.stevedale.tv


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Positively Expert: Steve Dale

Steve is a certified dog and cat behavior consultant, has written several books, hosts two nationally syndicated radio shows, and has appeared on numerous TV shows including "The Oprah Winfrey Show," "National Geographic Explorer," and "Pets Part of the Family." Steve’s blog is www.stevedale.tv


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