Feline leukemia (FeLV), a widespread, incurable virus that typically suppresses a cat’s immune system, is the most common cause of cancer in cats. Although some cats are able to eliminate the virus on their own and develop immunity, many others die as a result of cancer or opportunistic infections.

The disease is spread from cat to cat through bites; mutual grooming; and sharing food or water dishes and litter boxes. Kittens can also contract the virus from their mothers.

FeLV is species-specific, so humans and dogs are not at risk.

In 2006, the Winn Feline Foundation reported that 3% of cats in single-cat homes were infected with FeLV. Infection rates are dramatically higher among stray cats and in homes where cats are allowed outside.

FeLV is highly contagious, so it is important to have your cat vaccinated if it could be exposed to other cats. The American Association of Feline Practitioners recommends all kittens receive the vaccine.

Infected cats may harbor the illness for several years with no signs of illness. Over time, they may lose weight, become depressed, or develop a fever. Their coats often deteriorate, and they may develop skin, bladder, or upper respiratory infections.

Your veterinarian can diagnose the disease by conducting a simple blood test called an ELISA.

Cats infected with the virus live an average of three years.

“Many of these cats can live reasonably healthy lives for a number of years if they receive proper care,” says Fred Scott, DVM, PhD, interim director of the Cornell Feline Health Center in Ithaca, N.Y.

If your cat is infected, good nutrition and a stress-free environment are essential.

“Your veterinarian will talk to you about the importance of maintaining a balanced diet. Also, he or she will ask you about your cat’s lifestyle and look for ways to reduce stress,” Scott explains.

Scott strongly recommends that infected cats be kept indoors so they won’t spread the virus. If you have multiple cats, have all of them tested, vaccinate any that are not infected, and consider housing infected cats separately.

“Your veterinarian will want to see your cat on a more frequent basis [than a healthy cat], say, every six months,” says Scott.

“Between check-ups, stay alert to your cat’s body condition. Once a month, rub your hand over its ribs. You should be able to feel them, but they shouldn’t stand out.”

If you notice any changes in your cat’s health or behavior, notify your veterinarian immediately.

This article originally appeared in PetsMatter Volume 3 Issue 4, published by the American Animal Hospital Association. Copyright © 2009 AAHA.

Reprinted with permission from the American Animal Hospital Association.