Animal Tales

by Dr. Howard A. Mintzer

Q. Ellen F. from East Fishkill writes: My veterinarian has recommended that I start giving my cat heartworm preventative. My friend's veterinarian doesn't think it's much of a problem and doesn't recommend the medication. I have had cats for years and have never used any heartworm preventative. What should I do?

A. Ellen, If you would have asked me this question a year ago I would have agreed with your friend's veterinarian. I, like many other veterinarians believed that heartworm disease was a rare condition in cats and that cats really didn't need to be protected. In the past year what I've learned about feline heartworm and the cases I have treated in my practice have made me change my mind. I now recommend that all the cats in my practice be receiving preventative. Heartworm is truly a problem in cats in this area and you are bound to hear much more about this disease in years to come. I think that within a year or two your friend's veterinarian will be recommending it also.

Veterinarians have always know that cats did get heartworm disease. Many of us have performed an autopsy on an otherwise healthy cat that died suddenly and were surprised to find heartworms in the heart. Because this happened so infrequently we felt and told our clients that heartworm was a rare condition in cats. Over the past two years it has become increasingly evident that we were wrong. Heartworm is a much more common disease in cats than we ever thought.

In the past few years quite a bit of research has been done in an attempt to determine the true incidence of heartworm disease in cats. Better tests now allow us to not only diagnose cats with heartworms in their heart, but more importantly diagnose the condition before it reaches the cat's heart. The new facts that we have learned has revolutionized how veterinarians understand heartworm disease in cats.

In the past we rarely found heartworm disease in cats because we were looking for the wrong disease. Here in Dutchess county we veterinarians are pretty good at diagnosing heartworm disease in dogs because we see so much of it. If cats got the disease it would look like the dog disease, right? So we looked for a disease of the heart just like we found in dogs. In the dog the disease begins with a cough and progresses over the course of a year or two with more persistent coughing, loss of weight, fatigue and finally heart failure and death. Put a drop of blood on the microscope and you often found many squirming heartworm babies among the blood cells. Heartworm disease in cats is different. First of all, there are almost never baby heartworms in the blood, and only rarely do adult heartworms reach the cat's heart. This disease in cats is primarily a disease of the lungs. In cats, it is a more acute disease, not a slow progressive disease that takes two or three years to kill. It is rare for a cat to go into congestive heart failure from heartworm disease. In its most violent form no symptoms are noticed before the cat is mysteriously found dead. More common symptoms can be wheezing either continuous or intermittent, coughing, vomiting and symptoms that look like a human having an "asthma attacks". Not all cats show all these symptoms. Some cats show no symptoms at all. In fact we now know that some of the cases we have diagnosed in the past as chronic bronchitis and asthma were in fact the cat form of heartworm disease. A feline heartworm test is now part of my standard workup for cats showing these symptoms.

Now that we know what to look for we are finding more cases of heartworms in cats. I have found and treated a number of cases in my practice here in Dutchess county. A recent study of cats in animal shelters in Japan showed that up to 25% of the cats had heartworm disease or had been exposed to heartworm disease. It is estimated that a cat has about ¼ of the risk that dogs do for getting infected with heartworm disease. Since heartworm disease is so common in dogs in our county it is easy to see why protecting your cat is so important.

Finally, protecting your cat is easy. Heartworm medicine can make a pet very sick if he has baby heartworms in his blood. That's why your dog is tested each year before renewing your prescription for heartworm preventative. Since baby heartworms are so very rarely seen in cat blood, your cat can safely start taking heartworm preventative without being tested for the presence of baby worms. The medicine is chewable, cats like it and it only has to be given once a month. It's a small price to pay for keeping your cat healthy.

If you'd like some more information, you can find it on my web page or you can send a stamped self addressed envelop to the office and I'll be glad to send the literature your way.