Two of the most devastating viral diseases for cats are
Feline Leukemia and Feline AIDS. Each is caused by a virus for which there is
no cure once a cat contracts it. Both viruses are in the family of viruses
called Retroviruses, which puts them in the same group as the Human
Immunodeficiency Virus. Fortunately, repeated studies of veterinarians who
routinely come in contact with these diseases, and repeated unsuccessful
attempts to grow these viruses in human cell cultures has confirmed that
neither virus is transmissible to humans.
For cats, these viruses are both spread by bite wounds, as
the virus is secreted from a cat’s body into their saliva. As opposed to HIV,
the Feline Immunodeficiency Virus is not a sexually transmitted disease.
Therefore, even spayed and neutered cats can contract feline AIDS without the
precondition of having mated with another cat.
These viral diseases have the same biological behavior in
cats as HIV does in humans. Initially, there is no indication that a cat has
become infected. Any cat with a bite wound from another cat may have been
exposed to either virus. In the case of the Leukemia virus, some cats will
mount an immune response and fight off the virus immediately after exposure.
However, the majority will not do so and will remain carriers of this deadly
pathogen. Cats that are exposed to the Feline Immunodeficiency Virus always
become carriers for life.
Most studies indicate that approximately 40% of cats exposed
to FeLV will fight off the virus, but the remaining 60% will remain infected
and die within 3 years. A small percentage will live longer. With FIV, the
average time to the onset of disease after a cat contracts the virus is much
longer—approximately 10 years. With
either virus the primary problem that develops is the same: the immune system
begins to fail, with consequences for a cat similar to those for people whose
HIV infection has progressed to the clinical disease of AIDS. Eventually,
almost all cats with either virus succumb to secondary bacterial infections and
other diseases. In some cases, cats with the Leukemia Virus will in fact
develop the cancer of leukemia (hence the moniker).
Research into possible treatments for these diseases has
largely been unsuccessful. There are reports that indicate the use of
Interferon as an oral medication given daily can help maintain a cat’s immune
function and thereby delay the onset of secondary infections. This has not been
documented by controlled studies.
The use of anti-viral drugs such as AZT used to treat AIDS
has been documented to be helpful, but is expensive and impractical for routine
use in cats. At present, it is considered that there is no cure for either of
these diseases.
There is an effective immunization against the Feline
Leukemia Virus, although none exists for FIV. (An immunization against FIV has
been developed and marketed by one pharmaceutical company, although the
American Veterinary Medical Association, the American Association of Feline
Practitioners and most veterinarians and veterinary immunologists recommend
against its use due to lack of data indicating efficacy).
Once it is known that a cat is a carrier of either virus,
that cat should be kept indoors thereafter to prevent it from interacting with
other cats outdoors. This eliminates the risk of transmitting the virus(es) to
unknown cats outdoors, and helps reduce the risk of secondary infections to the
known carrier. If a cat is confirmed as
a carrier of the Feline Leukemia Virus and is to be kept indoors, all other
cats in the house should be immunized against that virus.
If a cat is confirmed as a carrier of FIV, there are no
protective medical steps than can be taken to reduce the risk of transmission
to other cats in the household, apart from isolating the cats from each other.
Although FIV can only be transmitted through a bite wound contaminated by
saliva, it has been postulated that there is about a 5% chance each year that a
cat will contract FIV from another cat even without a bite wound. Whether this
is because there are unknown incidents of biting, or transmission occurs
through other contact with a carrier cat’s saliva, is not known.
Veterinarians generally recommend all new kittens and cats
have a blood test done to determine their status for these infections. Only
cats that go outdoors are at risk for contracting these infections, so at our
practice we do not recommend that indoor cats be immunized against the Leukemia
Virus. If a cat is to go outdoors also, it should be immunized against the
Leukemia Virus by receiving a series of two injections about three weeks apart,
followed by a booster shot a year later, and then a booster every 3 years after that. Again, there are not
preventive measures that can be taken to avoid FIV infection if a cat goes
outdoors and encounters other cats. By testing your kitten for these infections
we can begin to control the spread of these deadly viruses, and guarantee your
kitten and other cats you may already have, all have as healthy a life as
possible.
Dr. Utchen graduated from the University of
Illinois College of Veterinary Medicine in 1986. In 1989 he and Dr.
DeLano co-founded Norris Canyon Veterinary Medical Center in San Ramon,
which in the year 2000 became Bishop Ranch Veterinary Center. His
special interests are Orthopedic and Soft Tissue Surgery, Internal
Medicine, Emergency/Critical Care, Dentistry, and Anesthesiology/Pain
Management. He lives in San Ramon with his wife and 2 daughters and
their two Cavalier King Charles Spaniels, Tori and Gus.
