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Feline leukemia virus (FeLV)

Every Cat/Kitten has a blood test preformed to check for the Feline Leukemia virus before they are introduced to the cattery thus to keep *Transmisson from occuring and allows us to **Prevent exposure, so we can guarantee your Kitten/Cat will be free from FeLV and warn aganst the FeLV  vaccine since there is not a vaccine that offers 100% protection from the virus and serious side effects have also been reported as a result of FeLV vaccination. If you chose to vaccinate or expose your Kitten/Cat to untested felines it will be cause for void of the Breeder's Guarantee.

Virus classification

Group:Group VI (ssRNA-RT)



Species:Feline leukemia virus


Feline leukemia virus (FeLV) is a retrovirus that infects cats. FeLV can be transmitted between infected cats when the transfer of saliva or nasal secretions is involved. If not defeated by the animal’s immune system, the virus can be lethal. A disease caused by this virus is a form of cancer of the blood cells called lymphocytes (a leukemia).



The name stems from the fact that the first disease associated with the virus was a form of leukemia. By the time it was discovered that the virus was not the same as leukemia, the misnomer had already found its way into the vocabulary of pet owners.


Signs and symptoms

The signs and symptoms of infection with feline leukemia virus are quite varied and include loss of appetite, poor coat condition, anisocoria (uneven pupils), infections of the skin, bladder and respiratory tract, oral diseaseseizureslymphadenopathy (swollen lymph nodes), skin lesionsfatiguefeverweight lossstomatitisgingivitis, litter box avoidance, pancytopenia, poor grooming, recurring bacterial and viral illnesses, anemiadiarrhea, and jaundice.



Cats infected with FeLV can serve as sources of infection. Transmission is related to the subgroup (see below). Cats can possibly pass the virus between themselves through saliva and close contact, by biting another cat, through a litter box or food dish used by an infected cat (rarely happens)[citation needed], and from milk during nursing. Transmission can also take place from an infected mother cat to her kittens, either before they are born or while they are nursing.


Initially thought to survive only about 2 hours in a dry environment, and about 48 hours in a damp environment (such as a litter box)[citation needed] a new paper published by Cornell vets ( titled "Can FeLV survive in the environment?" likened FeLV to HIV (which can survive for several weeks in the environment[citation needed] and is structurally related to FeLV). In the absence of any meaningful studies in to the survival of FeLV in the environment, it may be sensible to exercise caution when assuming FeLV survival in the environment is so short (2 hours to 2 days).


FeLV causes immunosuppression in pet cats, and there is also evidence for existence of the virus in larger wild cat populations also (e.g. lynxcheetahs, and lions).


Overwhelming epidemiologic evidence suggests FeLV is not transmissible to either humans or dogs. This statement is based on the fact that approximately one pet dog in five lives with a cat, and all pet cats live with humans (some 60 million pet cats in the USA). It is species-specific, and does not infect other animals, such as dogs (in fact, there is apparently no canine version of this disease at all).


Approximately 0.5% of pet cats are persistently infected with FeLV, but many more pet cats (>35%) have specific IgG antibodies which indicate prior exposure and subsequent development of immunity instead of infection. Transmission of FeLV is mainly via saliva and friendly behaviors, such as sharing feeding bowls and mutual grooming (as distinct from fighting and biting).

There is strong evidence kittens under 4 months of age are susceptible to infection, but by 8 months are resistant to it.

Kittens can be born with it, having contracted it from their mother while in utero.

Infection is far higher in city cats, stray or owned, than in rural cats: this is entirely due to the amount of contact the cats have with each other.

Four subgroups of FeLV exist: A; B; C, and T, but only subgroup A is transmissible between cats. The other subgroups arise de novo and as results of recombination with an endogenous DNA feline sequence. Hence, there is very good evidence this virus is quite ancient, and may well have evolved more than one time over the last 10,000,000 years.

Subgroups are defined on the basis of viral interference and in vitro host range. The differences are due to polymorphism in the envelope glycoprotein gp70 with the highest level of divergence lying in the region of gp70 which is thought to interact with the cellular receptor. In an infected cell, gp70 is thought to block viral receptors, so preventing further infection by the same subgroup.



The disease has a wide range of effects. The cat can fight off the infection and become totally immune, can become a healthy carrier that never gets sick itself but can infect other cats, or a mid-level case in which the cat has a compromised immune system.[citation needed] Nevertheless, the development of lymphomas is considered the final stage of the disease. Although it is thought that virus protein has to be present to induce lymphomas in cats, newer evidence shows that a high percentage of FeLV-Antigen negative lymphomas contain FeLV-DNA, indicating a "hit-and-run" mechanism of virus induced tumor development.

Once the virus has entered the cat, there are six stages to a FeLV infection:

  • Stage One: The virus enters the cat, usually through the pharynx where it infects the epithelial cells and infects the tonsorial B-lymphocytes and macrophages. These white blood cells then filter down to the lymph nodes and begin to replicate.

  • Stage Two: The virus enters the blood stream and begins to distribute throughout the body.

  • Stage Three: The lymphoid system (which produces antibodies to attack infected and cancerous cells) becomes infected, with further distribution throughout the body.

  • Stage Four: The main point in the infection- where the virus can take over the body's immune system and cause viremia. During this stage the hemolymphatic system and intestines become infected.

If the cat's immune system does not fight off the virus, then it progresses to:

  • Stage Five: The bone marrow becomes infected. At this point, the virus will stay with the cat for the rest of its life. In this phase, the virus replicates and is released four to seven days later in infected neutrophils (white blood cells), and sometimes lymphocytes, monocytes (white blood cell formed in the bone marrow), and eosinophils(another white blood cell).

  • Stage Six: The cat's body is overwhelmed by infection and mucosal and glandular epithelial cells (tissue that forms a thin protective layer on exposed bodily surfaces and forms the lining of internal cavities, ducts, and organs) become infected. The virus replicates in epithelial tissues including salivary glands, oropharynx, stomach, esophagus, intestines, trachea, nasopharynx, renal tubules, bladder, pancreas, alveolar ducts, and sebaceous ducts from the muzzle.


Cats diagnosed as persistently infected by ELISA testing may die within a few months or may remain asymptomatic for longer. The fatal diseases are leukemiaslymphomas, and non-regenerative anemias. Although there is no known cure for the virus infection, in 2006 the United States Department of Agriculture approved Lymphocyte T-Cell Immunomodulator as a treatment aid for FeLV and/or FIV infections.



  • Non exposure


  • Vaccines for FeLV are available (ATCvet code QI06AA01 and various combination vaccines), though no currently available vaccine offers 100% protection from the virus. Serious side effects have also been reported as a result of FeLV vaccination.

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