The Heartbreak of Feline Heartworm -- and What You Can Do About It

Imagine the nightmare of your beloved cat coughing, wasting away, struggling to breathe, or even passing away suddenly for no obvious reason. That's the heartbreak of feline heartworm disease. Heartworm infestations can do severe damage to your cat's health or even threaten his life -- with fewer treatment options than those available for heartworm infestations in dogs. Let's take a look at heartworm disease, how it affects cats, and what you can do to protect your kitty against it.

Heartworms are so named because their long, spaghetti-shaped bodies live in the hearts and lungs of infested animals. But these worms don't actually enter your cat's body as worms; they begin as immature forms called microfilarie. Mosquitos pick up microfilariae from the blood of infested animals and then inject the larval worms into other animals through bites. Once in the bloodstream, the microfilariae find their way to the cardiopulmonary system and take up permanent residence there. As they grow, they do more and more damage to the heart, lungs, and blood vessels.


Heartworms may or may not produce recognizable symptoms during the 2 to 3 year they typically live inside a cat's body. The common signs of a possible heartworm infestation include:

• Breathing problems or coughing
• Loss of weight, vomiting, and/or lack of interest in food
• Difficulty walking, seizures, fainting spells, and other neurological symptoms

As terrible as this list sounds, even more shocking is the fact that heartworm can cause sudden death in cats that haven't even shown any symptoms. That's because as the worms die off, they release substances that can trigger fatal immune system reactions.

On the surface, cats would seem to have it better than dogs where heartworm is concerned. Dogs make a much more suitable host for the worms, sometimes hundreds hundreds of worms at a time, while a cat might harbor half a dozen worms at most. Heartworms also live longer in dogs than they do in cats (5 to 7 years as opposed to 2 to 3 years). But dogs don't experience the "sudden death" reactions that cats do -- which makes them much easier to treat for the condition than cats.

Heartworm treatment for dogs may be a risky, lengthy process involving months of drug therapy, but at least they have the option of undergoing such treatment. Cats can't receive drug therapy because of the danger of a deadly reaction to the dying worms. In many cases, the best your vet can do is treat your kitty's symptoms, keep him as healthy as possible, and hope that the worms will eventually die off harmlessly.