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Feline Leukemia and Feline Immunodeficiency Virus

| May 31, 2018
Feline Leukemia and Feline Immunodeficiency Virus

Once a cat has been infected with FeLV, it has the virus and, at this time, there is no known way to eliminate it from the cat's system.

Feline leukemia virus (FeLV) is a contagious and often fatal virus that is widespread in the American cat population. Once a cat has been infected with FeLV, it has the virus and, at this time, there is no known way to eliminate it from the cat’s system. The infected cat’s immune system is suppressed and thereby the cat becomes more susceptible to secondary infections. No breed of cat is more susceptible than another, but kittens and older or debilitated cats are more susceptible than healthy cats.

Mode of Infection

After being infected with FeLV, all cats will develop a low-grade level of the virus in their blood within the first two weeks. This infection will then progress in some cats, while others will successfully fight off the virus and not remain infected. All cats that develop the persistent infection serve as a source of infection for healthy, uninfected cats with which they come in contact. The virus is excreted primarily in the saliva, but may also be present in feces and urine. The major modes of spreading the virus are through social grooming, biting, sneezing, and sharing litterboxes or food bowls. Kittens can become infected from their mother in utero, or through her milk. Although feline leukemia is widespread in cats, a significant percentage of adult cats that are exposed to FeLV develop an immunity to the virus and do not become infected. Once outside the cat, FeLV is very unstable and is rapidly killed by drying (3-4 hrs), alcohol, and most common household detergents and disinfectants.

Symptoms and Diagnosis

Signs of FeLV infection arise from the various diseases it causes. The affected cat may lose appetite and weight, its mucus membranes may become pale, it may be constipated or pass bloody stool, and have difficulty breathing, coughing or swallowing. Most kittens born to infected mothers develop what is termed “fading kitten syndrome”. The kittens are lethargic, have stunted growth, and are susceptible to infection. A cat with FeLV may develop a number of diseases that are either directly or indirectly caused by the virus. Most common are various cancers, anemia, kidney disease,or secondary infections caused by a lowered immune response. With the weakening of the cat’s immune system, otherwise non-threatening conditions may prove serious or fatal. FeLV cats recover slowly from such infections (upper respiratory infections, bite wounds, abcesses) and can easily become severely debilitated.

Infection with feline leukemia virus is diagnosed by a blood test. Since a cat will test positive to FeLV even in the primary stage of the infection (when the cat’s immune system may still be able to fight off the virus), it is important that all positive tests are repeated in eight to twelve weeks to determine whether the infection is persistent.


There is no recognized cure for feline leukemia virus, and currently many cats will die within a year of diagnosis. Traditional treatments address the symptoms of the disease, and try to keep the cat as comfortable as possible. More recent approaches to cancer caused by FeLV include surgery, radiation therapy, and chemotherapy. Some holistic veterinarians have experienced success in treating feline leukemia with nutritional therapy, particularly through the use of vitamin C. This is a field of treatment that is not yet accepted by the medical community at large, although the licensed veterinarians who practice nutritional therapy claim significant success in treating FeLV cats. It is important to realize that FeLV-infected cats are capable of infecting other cats in the household. Because of the poor prognosis most veterinarians currently give for a FeLV cat to live a life of good quality, many people choose to euthanize their cat rather than pursue treatment and subject the cat to isolation from others of its kind. This is a difficult decision which must be considered on an individual basis. There is no evidence linking human illness to the feline virus, but many veterinarians recommend that contact with FeLV positive cats be minimized.


Many veterinarians feel that if you have only one cat and she is kept strictly indoors, there is little chance of the cat being exposed to feline leukemia virus. This is probably the best means of prevention. All new cats entering a multi-cat household should test negative. If you have previously had a cat with FeLV, wait at least 30 days before acquiring a new cat. During that time, all litterboxes and food bowls should be replaced, and the premises cleaned thoroughly.

Two vaccines are currently available for prevention purposes. Neither so far offers protection to more than 89% of cats inoculated, so the vaccine alone is not recommended as the sole means of prevention. Until a 100% vaccine is developed, additional measures should be taken. Keeping your cat indoors 24 hours a day is currently the best safeguard. However, any cat may be periodically in a high risk situation, and it may be wise to have the cat vaccinated for extra protection. A vaccination schedule can be started as early as nine weeks of age. Only those cats that are FeLV negative should be vaccinated. Three doses are required: an initial inoculation, repeated a second time two to four weeks later and again two to four months later. Thereafter a yearly booster is recommended to maintain immunity.

Feline Immunodeficiency Virus

FIV is a newly recognized feline virus. It is related to FeLV and displays many of the same signs: anemia, low white blood cell counts, and secondary infections. For some time, cats who showed symptoms of FeLV syndrome but who tested negative were nevertheless assumed to be carrying FeLV. Now a FIV test is available. FIV is not related to the human virus HIV, although many of the symptoms may be similar. FIV infection is restricted solely to cats.

Much remains unknown about FIV. The method of transfer is believed to be through bite wounds rather than casual contact. The virus may remain dormant for some time (up to years), during which the cat appears normal. As the immune system becomes affected, the cat is likely to contract secondary infections. It is these secondary infections that are responsible for most of the clinical signs associated with FIV infection.

There is no current treatment for FIV. Treatments used are to combat the secondary infections that arise. No vaccine is currently available. Protection can be assured only by preventing your cat from contacting infected cats. Cats kept indoors and away from free-ranging cats are highly unlikely to contract FIV infection.

Copyright & Credit:
Source: Paws –
Photo copyright and courtesy: Duygu Agar – stock.xchng

Category: Feline Health, Feline Health and Care, Feline Resources

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