cat with mosquito on his nose

The information in this article has been reviewed and updated.

April showers bring May flowers, which we all look forward to after a long, snowy winter. Unfortunately, those same showers also bring mosquitoes, with their distinctive whine and itchy bites. But mosquitoes are more than just annoying: They’re carriers of a parasite that can kill your pet.

You’re probably way ahead of me. No worries, Doc, you say. I have my dog on heartworm preventive.

As any responsible dog lover should, I’d say. But what about your cat? Did you know that heartworm disease is also a problem in cats? If you didn’t, don’t beat yourself up. The problem is so little known it’s practically a secret to cat owners, but fortunately not to veterinarians.

Yes, cats can — and do — get heartworm disease. They’re not the ideal host for these parasites, though, and many cats are able to rid their own bodies of the pests. But for those cats who don't, heartworm disease can cause serious health problems and even death, so the risk shouldn't be ignored.

Heartworm Disease and Your Cat

The problem starts with a mosquito bite, which allows the microscopic heartworm larvae to migrate into their next victim. In dogs, these larvae eventually mature into adult worms that live in the lungs and heart; almost everyone has seen what a mess the adult worms make in clogging that vital organ. The risk of leaving them in the heart in dogs is deadly, so a treatment protocol is usually recommended, even if it isn't always easy or without side effects. That’s why using preventive medication is so essential in dogs.

In cats, the need for preventive medicine hasn't been so clear-cut. But we are becoming more aware that some conditions we’ve thought were something else were really heartworm disease, with evidence of larvae and immature or adult heartworms in the cats' bodies. As these health problems become easier to identify as heartworm-related, I suspect we’ll see feline heartworm preventives in wider use.

How is the disease in cats different than in dogs? The signs of heartworm disease in dogs are usually associated with the accumulation of adult worms in the heart. Since cats can often eliminate worms before they reach the adult stage, they typically don't end up with a heart full of what looks like spaghetti. The problem in cats is that immature worms are capable of causing damage in the lungs, leading to breathing problems that are often mistaken for feline asthma.

Protect Your Feline

It’s difficult to offer any definitive advice that holds true for all cats in all parts of the country. In the Gulf region, for example, where heartworm is prevalent, cats as well as dogs are more likely to be threatened by heartworm disease. Where I live, in extreme North Idaho, it’s nowhere near as big a problem. That said, heartworm disease has been diagnosed in all 50 states of our country.

As always, your veterinarian is your guide for information on how preventing heartworms fits into your cat’s wellness plan. Whether you live in a high-risk area or not — even if your cat lives indoors — talk to your vet about having your cat tested for the presence of heartworms. Based on the results of that testing, you and your veterinarian will be able to make an informed decision with regard to preventive medication. If you and your vet decide that heartworm preventive is the right move, your veterinarian can prescribe one of a handful of FDA-approved medications that are effective at preventing heartworms from living in your cat.

Make sure you bring the subject up at your cat’s next wellness exam. Because heartworm isn’t just a problem for dogs, and cats deserve protection, too.

More on the topic: 5 Myths About Feline Heartworm Disease