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Feline Leukemia Virus Infection (FeLV) in Cats

Feline leukemia virus (FeLV) is a disease that impairs the cat's immune system and causes certain types of cancer. This virus is responsible for a majority of deaths in household cats, affecting all breeds. Males are more likely to contract the infection than females, and it is usually seen between the ages of one to six years old.

Symptoms and Types

Signs depend on the type of infection: FeLV-A, FeLV-B, or FeLV-C. Cats found with the virus can be infected with one, two, or all three types.

FeLV-A:

• Occurs in all cats infected with FeLV. It severely weakens the immune system (immunosuppression).

FeLV-B:

• Occurs in about 50 percent of FeLV-infected cats, and causes tumors and other abnormal tissue growths.

FeLV-C:

• The least common type, occurring in about 1 percent of FeLV-infected cats. It causes severe anemia.

Of these types, some of the more common symptoms include:

• Anemia
• Lethargy
• Weight loss
• Abscesses
• Enlarged lymph nodes
• Persistent diarrhea
• Infections of the external ear and skin
• Fever (seen in about 50 percent of cases)
• Wobbly, uncoordinated or drunken-appearing gait or movement
• Inflammation of the nose, the cornea, or the moist tissues of the eye
• Inflammation of the gums and/or mouth tissues
• Lymphoma (the most common FeLV-associated cancer)
• Fibrosarcomas (cancer that develops from fibrous tissue)

Causes

FeLV is usually contracted from cat-to-cat transmission (e.g., bites, close contact, grooming, and sharing dishes or litter pans). It can also be transmitted to a kitten at birth or through the mother's milk. Kittens are much more susceptible to the virus, as are males and cats which are allowed to go outside.

Diagnosis

Your veterinarian will first rule out other infections such as bacterial, parasitic, viral, or fungal. In addition, nonviral cancers need to be ruled out.

A complete blood count is done to determine if the cat has anemia or other blood disorders. Diagnosis may also be determined by conducting a urinalysis, or through a bone marrow biopsy or bone marrow aspiration (removing a small amount of marrow fluid for study).