The feline leukemia virus is excreted in saliva and
tears and possibly the urine and feces of infected
cats. Prolonged, extensive
cat-to-cat contact is required for efficient spread, because the virus is
rapidly inactivated by warmth and drying.A cat with FeLV disease may live for several weeks to
several months, depending on how advanced
the disease is at the time of
diagnosis. However, it is impossible to tell how long any particular cat
will
survive.
A significant percentage of adult cats that are exposed
to the virus develop immunity and do not
become persistently viremic (i.e., will
not carry the virus indefinitely in the blood and bone marrow).
Usually those
cats live out a normal life span. However, in some the virus may remain
sequestered
for a variable period of time somewhere in the body. It is thus
conceivable that FeLV might break
out and cause disease at a later date, after
the cats have been stressed, or perhaps medicated
with drugs that suppress the
immune system.
Although the possibility that FeLV can be transmitted to
human beings and cause disease cannot be
ruled out completely, there certainly
is no evidence to date that transmission does occur, despite
decades of
extensive research. Also, there is no known association of FeLV with acquired
immune deficiency syndrome (AIDS) in human beings. It is true that FeLV can be
grown in human cells in
culture; the same is true of other infectious disease
agents that nevertheless do not produce
disease in human beings. Similarly there
is no evidence that FeLV is carried by, or causes any illness,
in dogs.
Common clinical signs produced by FeLV include anemia,
jaundice, depression, weight loss, decreased appetite, diarrhea or constipation,
blood in the stool, enlarged lymph nodes, respiratory distress,
decreased
stamina, excessive drinking and urination, fetal resorption, abortion,
infertility, birth of
"fading" kittens, and a syndrome resembling panleukopenia ("cat distemper"). FeLV also interferes with
the cat's
natural ability to ward off infectious disease agents, so that almost any
severe, chronic
illness may lead your veterinarian to suspect FeLV.
Cancer occurs in some FeLV-infected cats. In those cats
the tumor masses may cause such problems
as respiratory distress; intestinal
inflammation with diarrhea, vomiting or constipation; liver or kidney disease;
cloudy eyes; and neurologic abnormalities.
Even if two or more successive tests reveal your cat to
be truly positive, it will not necessarily die.
An FeLV-positive healthy cat may
live for months or years; the life expectancy is impossible to predict. Your cat
is probably shedding virus that could infect other cats, however, and you should
take
precautions to reduce the chance of spreading the disease. In addition, the
body's reaction to the
virus may protect it from the primary FeLV disease
problems but not from the immune-system
suppression that the virus also can
cause. Your cat thus may be much more susceptible to other
infectious diseases
and will require careful monitoring and immediate treatment should illness
become apparent.
To date there is no cure for FeLV infection or disease.
A variety of chemotherapeutic regimens have
been developed, and in certain cases
those regimens can produce a temporary remission, depending
on the physical
condition of the cat and the type of disease that is present. Those drug
therapies may allow the cat to continue in a reasonably healthy state for a
period of several weeks to several months. However, it must be understood that
those are only remissions and not permanent cures. Chemotherapeutic drugs are
very potent, and their effects must be monitored carefully, to avoid overdosing
the patient.
Various antiviral compounds including interferon may
also be used to treat cats with FeLV infection.
Those compounds, while still
experimental, are generally safer to use than chemotherapeutic agents,
and may
reduce the amount of virus present in the blood of the cat, and may extend the
period of remission of clinical disease. As yet, antiviral compounds do not
produce permanent cures for FeLV
infection or disease. Hopefully, additional
research will produce effective antiviral therapies that will
cure FeLV disease.
There is no scientific documentation that vitamin C
cures cats of leukemia. Controlled studies of feline
viral rhinotracheitis,
canine distemper, and human respiratory infections have failed to show
effectiveness of high doses of vitamin C. Of course, a multivitamin and mineral
supplement may be
helpful to any sick animal that is not eating properly;
however, there is little evidence to support
claims that such a supplement can
cure any of those conditions. Other than providing general support
to the
animal's health, vitamin and mineral supplements, in our estimation, are not
effective in
preventing the spread of FeLV within a cattery and certainly will
not cure an individual cat of its
infection.
Therapy with a steroid (such as prednisolone) acts to
decrease the numbers of some circulating white blood cells (lymphocytes). A cat
with leukemia may have an increased number of abnormal (cancerous) lymphocytes
circulating in its bloodstream; therefore steroid treatment may help to destroy
them. Prednisolone may also act directly against the cells of some solid tumors
(such as lymphosarcoma) that
are caused by FeLV. Steroids also inhibit the cells
that are normally responsible for destroying senescent red blood cells; that
effect may help to combat the anemia and excessive red blood cell destruction
that often accompany FeLV.
It is important to remember that because steroids and
FeLV both suppress the immune system, an
FeLV-positive cat undergoing steroid
therapy is especially vulnerable to other infections.
Several vaccines are now available to aid in the
protection of your cat against FeLV infection. The vaccines are produced by
various methods, and either contain the inactivated ("killed") whole
virus,
or a subunit protein of the virus. The principle of protection is the
same for each of these vaccines.
The FeLV vaccines are as safe as other commonly used
feline vaccines. As with any vaccine in animals
or humans, some reaction to the
vaccine may occur in a relatively small number of vaccinations. The
vast
majority of cats vaccinated with FeLV vaccines will experience no reaction at
all. Occasionally,
your cat will experience some malaise for a few hours or for
a day or two after vaccination. On rare occasions, an allergic reaction to one
of the components of the vaccine may occur which will result in fever, diarrhea,
and malaise. This allergic reaction can be treated by your veterinarian.
The FeLV vaccines are reasonably effective in preventing
persistent FeLV infection should your
vaccinated cat be exposed to the virus. No
vaccine is 100 percent effective, and this is true for the
FeLV vaccines. The
immune response produced by these vaccines will protect most exposed cats from
becoming infected with the virus. Occasionally after exposure to the feline
leukemia virus, a vaccinated
cat will develop a transient viremia (temporarily
become FeLV positive for up to 12 weeks), but the
immune response produced by
the vaccine will control the virus such that these cats will not develop
clinical disease. Unfortunately, a small percentage of FeLV-vaccinated cats will
not be protected
against exposure to FeLV.
Kittens should be vaccinated twice starting at nine to
ten weeks of age, with the second dose of the vaccine given three to four weeks
later. Your cat should receive annual revaccinations ("booster"
vaccinations) against FeLV.
The FeLV vaccines are not 100 percent effective, and
thus a degree of risk occurs when a vaccinated
cat is housed with a
persistently-infected cat (FeLV-positive cat). It is recommended that
FeLV-
positive cats not be housed with FeLV-negative cats, even those that have
been vaccinated.
Certainly, a cat vaccinated against FeLV will have a far
greater chance of successfully withstanding
an exposure to FeLV than an
unvaccinated cat.
No, vaccination will not interfere with either the ELISA
or IFA diagnostic tests. The vaccines do not
contain living virus, and the
diagnostic tests detect a specific protein within the virus. Antibodies
against FeLV, produced as a result of vaccination, are not detected by the diagnostic
tests.
In either a cattery or a multicat household, the most
effective procedure is to test by IFA and remove
all FeLV-positive cats. The
remaining FeLV-negative cats should then be vaccinated and retested
every three
to six months for the next year, and any that become positive during that time
should be removed. The household cannot be considered "free" of FeLV
until all remaining cats have tested
negative in two sequential tests taken at
least three months apart. No new cats should be brought
into the household until
all the cats already there test negative repeatedly. All new cats should test
negative initially, be quarantined for at least two months, and retest negative
before being allowed to mingle with other resident cats.
The premises should be routinely scrubbed with detergent
or disinfectant and wiped down with a
solution containing four ounces of
household bleach per gallon of water (bleach is an excellent
disinfectant for
viruses and other infectious disease agents). All food and water bowls, bedding
material, and litter pans should be thoroughly cleaned and disinfected. Better
yet, they should be
replaced.
Feline leukemia virus is relatively unstable and will
not survive outside an infected cat for an
appreciable length of time. The
Cornell Feline Health Center recommends a waiting period of at least
thirty days
after removal of an FeLV-positive cat before a new cat is acquired. Other
precautions that should be taken are identical to those described above to
protect healthy cats. Thoroughly disinfect or replace the food dishes, litter
pans, and bedding that were used by the infected cat. Floors that are covered
with tile or other hard surfaces should be cleaned and then disinfected with
dilute bleach
solution (4 oz. household bleach to 1 gal. water). Thorough
vacuuming of rugs, plus the thirty-day quarantine, should be sufficient to
eliminate the virus from carpeting in the household.
Removal of persistently FeLV-positive (positive on the
IFA test) cats from a household is the only
proven effective method for FeLV
control. The question naturally arises: what is to be done with such
cats after
their removal? In the past, some have recommended euthanasia (because there is
no reliable means of eliminating the virus from the cat's body, the cat itself
must be destroyed, to destroy the
virus). Euthanasia has also been put forth as
the only effective means for preventing further spread of FeLV within the cat
population at large. The question of euthanizing a positive cat is one that must
be addressed in each individual case, in consultation with the attending
veterinarian. Vaccination against
FeLV does not completely replace testing and
removal as the method of choice for controlling FeLV.
If you own only one cat and it is FeLV-positive,
euthanasia is not necessary from the standpoint of controlling virus
transmission, so long as you keep your cat indoors and away from all other cats.
You
must remember, however, that in time the cat may develop an FeLV-related
illness and become so uncomfortable that euthanasia becomes the only humane
course of action.
If you have only a few cats and are reluctant to have a
positive one destroyed, particularly if it is
clinically healthy, a strict intrahousehold quarantine program may permit you to protect your other
cats from
infection. The FeLV-positive cat must be prevented from having any contact with
the
negative cats, perhaps by housing it in a separate room within the house.
Separate feeding utensils
and litter pans should be provided, and hands should
be thoroughly washed and clothing
(including shoes) after handling and caring
for the positive cat. The positive cat should never be
allowed outdoors, where
it might come into contact with FeLV-negative cats and transmit the virus.
Feline leukemia virus is transmitted from carrier queens
to their kittens either in utero or after birth.
A very high percentage of
kittens born to infected queens will succumb to FeLV infection or FeLV-
related
disease. In our estimation it is absolutely essential that you establish a
test-and-removal
program, so that all persistently infected animals are removed
from the cattery. Continuing to breed
FeLV-positive queens merely expands the
problem and in essence signs the death warrant of kittens
born to those queens.
Our research on FeLV has involved basic studies of the
virus itself; attempts to develop more effective vaccines; and evaluations of
the effectiveness of current FeLV vaccines, therapies, and diagnostic tests. Our
efforts are directed toward eliminating forever the threat of this devastating
viral infection.
Join
Our 
