Pet Columns, Office of Public Engagement, College of Veterinary Medicine at the University of Illinois at Urbana-Champaign

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Cats Get Heartworm Disease, Too

Pet Column for the week of March 9, 2009

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Ashley Mitek
Information Specialist

Most dog owners are well aware of the deadly consequences a heartworm infection can have on their pet and strictly adhere to monthly preventatives. However, many cat owners are unaware that their pets are susceptible to these parasites as well, even if their feline friend lives only indoors. Because clinical signs of heartworm disease in cats are sometimes mistaken for other ailments, the disease may go undetected.

"Feline heartworm disease is very difficult to diagnose, but easy to prevent," says Dr. Allan Paul, a veterinary parasitologist at the University of Illinois College of Veterinary Medicine. Because the disease is complex, testing for the parasites in cats can be confusing and, in most cases, more than one test is needed to make an accurate diagnosis.

Signs of heartworm disease in cats are somewhat nonspecific. Years ago the disease would have been diagnosed as feline asthma, but now veterinarians realize that cats can get heartworm disease, too. Coughing and difficulty breathing are two of the common symptoms. Unfortunately, "acute death is also one of the signs," notes Dr. Paul. Because the worms have a short lifespan of 2-3 years in cats, once they die this may cause an embolism resulting in immediate death.

Preventing heartworm disease is quite simple. Just as with dogs, there are monthly preventatives on the market you can get from a veterinarian. Because there is no treatment for the disease; prevention is the only cure. Dr. Paul also notes that most of the feline heartworm preventatives also kill other internal parasites that would be harmful to your pet.

Mosquitoes transmit heartworms when they feed on an animal. The spring brings warm weather and a flurry of mosquitoes carrying many diseases. Monthly preventatives inhibit a certain stage of the parasite to prevent growth in the animal's heart and lungs. Although dogs are the preferred host of heartworm disease, and cats are more resistant to the worms, our feline friends most certainly are not immune.

Data from the American Heartworm Society indicates that the disease is most prevalent in the southern United States and along the Mississippi River. Because the parasite is spread by mosquitoes, waterways are a highly endemic area.

Current research has also shown that the pathology of heartworm disease in cats is somewhat different than that in dogs. Despite being called "heartworms" the disease in cats mostly affects the lungs. In contrast to canine infections, data has shown that even immature worms can cause severe problems in the lungs of cats. Furthermore, when a common blood test indicates that worms are not present, the disease may still be ongoing, or in the early stages, and starting to damage lung tissue.

Dr. Paul recommends that you talk to your local veterinarian if you have questions about placing your cat on preventatives. For more information you can visit the American Heartworm Society's Web page for cat owners at