Feline Leukemia Virus is a retrovirus that infects cats. Transmission usually occurs when the transfer of saliva or nasal discharge and secretions are involved. It is transmitted as an RNA virus and is reverse transcribed into the DNA.

Signs and Symptoms

Signs that your pet might be infected vary and can be greatly affected by stress levels, so keeping your pet at a consistent, content emotional state is always advantageous.

A stressed cat might avoid the litter box or experience a loss of appetite or incontinence. Other signs include poor self grooming, bladder and respiratory tract infections, oral disease, fever, fatigue, skin lesions and jaundice.

Stomatitis, pancytopenia, and lymphadenopathy, as well as reoccurring bacterial and viral illnesses are all common as the affliction changes throughout the different stages.

Kittens can contract it from their mother in utero or during nursing. Otherwise healthy kittens seem to be susceptible to infection under the age of four months, but by the age of eight months appear to be resistant.

Infection is higher in city cats than in rural cats. Less than 1% of pet cats are infected with FeLV, but many more cats (over thirty percent) have specific antibodies that indicate prior exposure and spurned the development of immunity rather than infection. If the virus can not be defeated by the cat's immune system, the disease can be terminal A cat can fight the infection and become immune yet still be a carrier to go out and infect other cats. It has been said that this is a very ancient virus, perhaps evolving more than one time over the last ten million years.

FeLV causes immunosuppressant in domestic cats and does not infect, dogs or humans, even though the viruses are structurally related…..and cats are the sources of their own infections: biting, grooming, saliva, close contact/friendly behaviors, litter boxes and food bowls.

While forty percent of cats are healthy enough to deal with the affliction, sixteen percent or so are able to fight it due to minimal contact. In twenty percent of cases, the infection slips into a state of latency, and remains that way until the cat becomes stressed, at which time it will resume. About thirty percent of animals see the disease through to completion, resulting in death.

The timeline for symptoms: sixteen to eighteen weeks after the FeLV virus is introduced.

The six phases of infection:

Phase One

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

Phase Two

The virus enters the blood stream and begins to distribute throughout the body.

Phase Three

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

Phase Four

The focal point in the infection, where the virus can take over the body's immune system and cause viremia. During this phase the hem lymphatic system and intestines become infected.

If the cat's immune system is unable to withstand the virus:

Phase 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 neuttrophils (white blood cells), and sometimes lymphocytes, monocytes (white blood cell formed in the bone marrow), and eosinophils (another type of white blood cell).

Phase 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, or pharynx, stomach, esophagus, intestines, trachea, nasopharynx, renal tubules, bladder, pancreas, alveolar ducts, and sebaceous ducts from the muzzle.


Any of a group of viruses, many of which produce tumors, that contain RNA and reverse transcriptase, including the virus that causes AIDS.

RNA virus:

Any of a group of viruses whose nucleic acid core is composed of RNA, including the retroviruses and picornaviruses

Stomatitis is an inflammation of the mucous lining of any of the structures in the mouth, which may involve the cheeks, gums, tongue, lips, throat and/or the roof and floor of the mouth.

Pancytopenia is a medical condition in which there is a reduction in the number of red and white blood cells, as well as platelets.

Lymphadenopathy is a term meaning "disease of the lymph nodes", and most often used synonymously used with "swollen/enlarged lymph nodes".