03/27/2012 08:32 am ET

Your Cat May Need Protection From Heartworm

By Dr. Marty Becker for Vetstreet

It's not really spring until you've smacked your first mosquito. Some mosquitos, though, are more than annoying bloodsuckers: They're carriers of a parasite that can kill your pet.

You're probably 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 lovers, but fortunately not to veterinarians.

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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 the fact that heartworm disease is different in cats than in dogs doesn't mean the risk should be ignored.

The problem starts when a mosquito bites, allowing the microscopic heartworm larvae to migrate into their next victim. In dogs, these microfilariae mature in the 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 enough that a treatment protocol that's anything but easy is used to rid the pet of the pests. 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 microfilariae elsewhere 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.

Why is the disease in cats different than in dogs? Because cats aren't a natural host for heartworms, and over time, many cats are able to rid themselves of the parasites without medical intervention. But just because cats don't always end up with a heart full of what looks like spaghetti doesn't mean the juvenile stages of the worms aren't capable of damage. Cats who have problems breathing are typically diagnosed with asthma, but breathing problems can be associated with the juvenile stage of heartworms. It's even possible for heartworms to kill a cat, typically too quickly for a veterinarian to be able to help.

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.

As always, your own veterinarian is your guide for information on how preventing heartworms fits into your cat's wellness plan. If you're in an area of high risk -- even if your cat lives indoors -- you may need to have 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. In areas of the highest risk of infestation, 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.

For more on pet health, click here.

Flickr photo by Cody Ellis