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

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Felv and Fiv: Compelling Reasons to Keep Kitty Indoors


Pet Column for the week of June 11, 2001


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

While it may be tempting to let your cat roam the great outdoors when the weather gets nice, there are some compelling reasons to keep your pet indoors. FELV and FIV are diseases that systematically destroy the immune system and render the body unable to defend against even the most common infections.

FELV, which stands for feline leukemia virus, infects bone marrow and other tissues. FIV, or feline immunodeficiency virus, infects white blood cells, rendering them unable to protect the body from infection. In both cases, the method of attack on the body is indirect, so there are no specific symptoms of disease that can be used to make a diagnosis.

Dr. Christine Merle, a veterinarian formerly at the University of Illinois College of Veterinary Medicine in Urbana says, "In most cases, it is not the virus that kills these animals, but secondary problems and secondary infections brought on by a suppressed immune system. The reason these diseases are so serious is that there is no cure for them. If you have an animal that is suffering from repeated infections and that seems to have an overall unhealthy appearance, it would be a good idea to test for both FELV and FIV."

Both diseases are spread through intimate contact between two cats. Dr. Merle says, "There must be transmission of the virus from one cat directly into the bloodstream of another cat." This means that while the virus is present in the saliva of the infected cat, it must be introduced into an opening in the skin such as a scratch, skin sore, or wound. Bite wounds are a perfect means of transmission for both of these diseases. Mother cats can also transmit them to kittens before they are born. Animals that live together and groom each other excessively are at a higher risk of spreading these diseases to one another through exposure to each other's saliva.

It was once thought that while FELV was relatively widespread, FIV was less contagious and limited primarily to older cats that had received bite wounds during fights. Veterinarians now believe that FIV is fairly prevalent. For this reason it is recommended that all cats coming to a new home, including kittens, be tested for both diseases before allowing them contact with other cats already in the household. Testing requires only a few drops of blood and can be completed in just a few minutes by your veterinarian.

For cats in a high-risk category, (e.g., those that go outside regularly) there is a vaccine for FELV. It is 80 to 90 percent effective at establishing immunity against FELV and therefore does not guarantee that your cat will not contract FELV if exposed. There is no vaccine currently available for FIV. For this reason the only effective means of preventing FIV infection is to keep your cat indoors, where it can't be exposed to potential carriers of these diseases.

Some animals live for years with these diseases without showing symptoms, and many can lead relatively normal, healthy lives for some time before the virus starts to take its toll. If the pet is in good health and the owner is willing to deal with possible health problems in the future, there is no reason not to continue to cherish an infected pet. To prevent the spread of disease, the infected cat should be kept in a closed household in which no other cats are introduced, and the infected animal should not be allowed to go outside.

Both FIV and FELV are debilitating and incurable diseases. The most effective method of preventing these illnesses is to limit exposure. Your cat may miss having the run of the neighborhood, but this policy may save you and your pet a lot of heartache in the long run.