The Carlisle Mosquito Online

Friday, May 4, 2007


Mosquitoes spread heartworm disease to cats

Whether humans are the cause of global warming or not, the fact is, the climate seems to be changing, and the earth is warming up. The result for those of us residing in mosquito-laden Carlisle is warmer winters and yet more mosquitoes. The consequences for our pets are potentially serious. Dog owners are likely well aware of the dangers of heartworm disease. I recommend monthly heartworm preventative for all dogs all the time, even through the winter months — the medication works.

Heartworm disease in cats has only recently begun to be well understood. We have known for a while that cats can get a heartworm infection, but now we are beginning to understand that it is not just the adult heartworms that are the problem. The mosquito injects a baby heartworm (larva) into your cat's body which then develops into a teenager worm. In most cats, the teenager worm does not complete its development into an adult heartworm, but instead wreaks havoc on your cat's lungs. Heartworm Associated Respiratory Disease (H.A.R.D.) is a new syndrome being described in the cat.

In the cat, heartworm disease is a lung disease for which there is no safe treatment. The treatment used in dogs is fatal to cats. Sudden death is not an uncommon manifestation of feline heartworm disease. We speculate that this could be another explanation for cats that suddenly disappear.

Those cats that show signs of heartworm disease may exhibit anorexia (failure to eat), coughing, tiredness, vomiting, weight loss, collapse, blindness or difficulty breathing. There is no way to test a cat for the presence of H.A.R.D. In fact, we now think that many cats diagnosed with feline asthma may actually have heartworm disease. Fortunately, the management of feline asthma and heartworm disease are the same: steroid therapy (by pill or inhaler), airway openers (by pill or inhaler), and monthly heartworm prevention.

All cats, whether they go outdoors or not, should be on regular monthly heartworm preventative. A mosquito can get into your home any time you open a door or a window — especially here in Carlisle! Heartworm prevention works retroactively. This means that it kills baby or teenager heartworms that were introduced into the body of the patient in the past months. Heartworm prevention comes in the form of oral, flavored chewable tablets (Heartgard®, Interceptor®) or topical applications (Revolution®, Advantage Multi®). I encourage cat owners to use the topical products as they also will kill fleas. The main disadvantage is that these can cost a little more. The chewable tablets are less expensive and certainly very effective in preventing H.A.R.D. in cats.

The American Heartworm Society is teaming up with the American Association of Feline Practitioners and Pfizer Animal Health in a new major public awareness campaign about this completely preventable disease. See to view comprehensive information about heartworm disease in cats and dogs. Finally, ferrets are also susceptible; don't forget to protect these little friends every month too.

Dr. Tiffany Rule is a Carlisle resident and veterinarian at Countryside Veterinary Hospital. She can be reached at

2007 The Carlisle Mosquito