Understanding Heartworm Disease In Cats

Many decades ago, veterinarians didn’t 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,” says Dr. Stephen Jones, president of the American Heartworm Society.

What to look for

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 suggests one worm is enough to cause permanent damage.

Unfortunately, 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 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 the cause of death.

“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.

Prevention pays

Are veterinarians and veterinary technicians doing enough to support prevention?

The data is revealing. 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 checkups compared to dogs, they may have a very specific reason for being at a vet clinic. Perhaps the cat suffered an injury or is being diagnosed with diabetes or even cancer. So, often 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.

Indoor cats are vulnerable

Cat owners may believe that keeping their cat indoors is enough sense, and that may have some validity if the cat is truly indoors and they live on the 45th floor of a high rise. But then again, 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 their definition of indoors might include a porch that isn’t quite mosquito-proof or include a backyard that is anything but mosquito-proof.

“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, but for cats, there is no heartworm treatment available. Arguably, heartworm prevention in cats is as priceless as the cats themselves.